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June 7 -8,2007 Lecturer Professo r Phil Hopkins
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IRGANIZED BY
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SUPPORTED BY
Defect Assessment in Pipelines June 7-N, 2007, Houston
Organized by Cl arion Technical Conferences 3401 Lo uisiana Street, Houston, Te xas 77002 , USA T el. 7 13.52 1.5929 . Web: www.clarion.org and G lobal Pipeline Mo nthly PO Rox 21, Beaco nsfield, Bucks HP9 INS, UK Tel. 44 1494675139 Web: www.pipcmag.com
Co pyright © 2007 Pcn spcn Gr oup . All rights reserved. This publicat ion may not be reproduced in any form wi thout pe rmi ssion of the copyright ow ners. For information contact Clarion Techn ical Conferences .
De fe ct As s e s sment in Pipelines
Course Progra m
1.
Course In t rod uct ion
2.
Introduction t o Oil , Ga s, a nd Pipeli nes
3.
In t rod uct ion to Pipeline Design, Con struction , a nd Op eration
4.
How Safe Ar e Pipeli n es a nd Why Do Th ey Fail ?
5.
In t r odu ction to Fract ure Mechanics (notes only)
6.
How to Assess Fatigue (notes on ly)
7.
How to Assess Defects
8.
Assessment of Corrosion
9.
Assessment of Gouges
10.
Ass essment of Dents
11.
Assessment of Cracks
12.
Assess ment of Weld Defect s
13.
Fract ure P ropa gat ion and Arrest (not es only)
1,1.
Intelligent P ig Inspection
15.
Pipeli ne Re pair a nd Reh abi lita t ion
16.
Risk Managem en t
17.
Respon sibilities, Moral s and Ethics
18.
Tutoria ls
Defect As s essme n t Cours e Schedu le
Day 1 8.00
Introduction, lectures
9.15
Coffee
s.ao
Lect ures
10.45 Coffee 12.00 L un ch
LOO
Lect u r es
2.15
Coffee
2.30
Lectu r es
3.4 5
Coffee
5.00
End of Day 1
Day 2
8.00
Lectures
9.15
Coffee
9.30
Lect u r es
10.45 Coffee 12.00 Lu nch
LOO
Lectu re s
2.15
Coffee
2.30
Lect u r es
3,.15
Coffee
4.45
End of course
Lect ure r
Professor Phil Hopkin s has more than 26 years' experience in pipeline and marine engineering, and is Technical Director with Penspen In tegrity and Visiting Professor of Engineering at the University of Newcastle-upon.Tyne. Phil has worked with most of the major oil and gas companies and pipeline companies around the world, providing consultancy on management, business, design, maintenance, inspection, risk analysis and safety, and failure investigations . He is th e current chairman of the Executive Committee of the AS),IE Pipeline Systems Division and has served on many other professional committees , including the Bri tish Standards Institution, European Pipeline Research Group, the American Gas Association's P ipeline Research Committee, and the DNV Pipeli ne Committee. P h il has extensive experience in both lecturing and training, and he regularly presents on many aspects of pipeline engineering at international industry meetings and seminars. More than 1500 engineers and technica l personnel around the world have attended his Pipeline Defect Assessment and P ipeli ne Integrity-related courses .
PIPELINE DEFECT ASSESSMENT COURSE PDAC
A Course by:
PENSPEN,UK World Leaders in Pipeline Integrity Training
COPYRIGHT AND DISCLAIMER Co pyr ight 2 0 07 by Penspe n G ro~ p All ri gh t s re served . No p a'-t 0 1 t t es s c our se n o te s may b e rep ro duc ed , d i st r i but e d o r store d or. a.ny for", o r b y a ny me a ns wit h out th e pr i or writ ts r. au t ho r isat io n o f the Penspen Group . Some of t he i mag es i n t l:e s e cour se no t e s l ave been s up p l i ed co n rt es y o f o t ter o r g~ r. j s~t ;ons or i nd i viduals , ~ nd t he s e ~r e acknowl edge d Some o f the i n ~ o rma t i onima t e r i al
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t a k en fro m t he l ite ra tu r e / int e rne t and i s fu ll y
Th e litera ture ! 'Ne bsite s ho u l d b e c on sul ted t or t he ~ o p y ri g h t t e r ms. cop yri gh t of e h es e mat:e , -ia ls re"a i:l s ~·it r. t h e ori gina l c o pyr ig ht ho l der .
re~erence d .
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cours e ho te s ha ve b een pre pared by penspen I nt eg r i t y Ipart at t he P e h s p e ~ based On i~ < Qrmat i on
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ACKNOWLEDGEMENTS The c au , s e
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aC kn o wl e d g e the i r co ll e a g ·~ e s . a r:d .,r",, ' ou s cou r s e a~tend e e ~. f o r tLeir' many c ornme n t s and Buggestior.s f or irr.proving t~.1! c o ur se non",. ':"he authors also t ha r.k thos e i n ctiv iduala a nd com p a n i e s ~' h o h,;v" sUl'pl ie1 some 0 1 t he i ma g " " in th.. "e CO"ree n o t e s .
Defect Assessment in Pipelines Houston, USA. June 2007
Phil Hopkins PENSPEN INTEGRITY
World Leaders in Pipeline Integrity Training Hav.' bom Sun" LOlL' ?&: k. Terrac:e w 'e! Sf Peter. Wharf St. Pc""" '$ Ba"" ~ .... ca'tle upon Tyno: "F~ 1 rz OK Tel H (/)) IV! 2.l X 1201! f,n 44 ((Ii 19/ .'Jj 97x6 ~",,,il "'Ngril,<'. "d:ii14·".'p~n.,·om ""w. f'
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Welcome ::J W elcome ... to the Pipel ine Defect
Asse ssment Course
::J Penspen is a UK based pipe line engineering consultancy com pany. ::J Part of our business is training pipeline eng ineers allover the wo rld, and we welcome any comments, or feed back, on this cou rse programme. :J
Please contact us with you r comments u Contact deta ils are on the front cover of this presentation.
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Penspen Group rr Pe nspen is owned by Dar AIHa ndasa h - 'House of Engi neers'
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Penspen has >1200 employees. u HQ is in Ric hmond , UK, but has offices around the world . o Works in oil, gas, water pipelines, and fac ilities eng ineering.
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Introduction o Introduce lecturers ...
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u and attendees """:IiIIIIII~.IIII
o Domestics u Help and Assistance
o Interaction o Course Timetable o Objective of Course o Reasons for Course o General Guidance Notes
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Domestics and Interaction Domestics
o T ea/Coffee o Lunch Breaks o Assistance ;:J Fire exits/procedures Interaction o It is YOU R course - interact! o Ask questions. pass comments, share your experiences o Vis it our website for more papers and articles on defect assessment:
www.penspenintegrity Qcom
Course Timetable
Day 1: 08.00
17.00
Day 2: 08.00
16.45
Worked Examples (during course)
Bring a calculator!
C _ U O 2001
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Course Timetable or
Introduction and Wel co me
or
Introduction t o Basi cs Pipel ine Engineering
or
W hy Pipelines Fail
... Introd uction t o Fractu re Mech an ics & Fat igu e (no tes o n ly)
or Fundam ental Pipel ine Def ect Fail ur e Rel ationsh ip s or How to Assess Corros io n Defect s or
How to Assess Gouges & Dents
or
How t o As sess Weld Defects
or
How to A ssess Cracks
or Fract ure Propagati on and Arrest (time perm ittin g) .... Setting Inte lligent Pig Inspectio n Levels
or Pipel ine Repa ir .... Pi peli ne Risk and Integrity Management & Tuto rial
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Objectives of the Course OBJECTIVE to underst and the :
reason for; behaviour or.'
assessment of;
consequences of; defect s in t ra nsm ission pipelines
AIM
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......
to give course attendees a sound . holistic I'comptete') understanding of defects in transmission pipelines, and the knowledge to allow asses sment
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Reason for the Course
Pipelines can cause fatalities:
Ghis leng ien, Belgium , July 2004 failure in a gas pipe line due to mechanical damage, ca us ing 23 fata lities
Reason for the Course
Car lsbad , New Mexico, August 2000 fail ure in a gas pipe l ine d ue to microb ial int erna l co rros io n, ca us i ng 12 fata lities
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Reason for the Course Pipelines can cause. .. Environmental damage
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Reason for Training: Safety rt A study conducted at the Swiss Federal lns lit ute of Techn ology in Zuri ch
analyzed 800 cases of structu ral failure in which 504 people wer e killed, 592 peopl e injured, and millions of do llars of dama ge incurred o Wh en engineers were at fault . the causes of failure were clas sifi ed as: In sufficient knowledge
36%
Underestimation of influence Ignoran c e, carelessness, n egligence
16% 14%
Fo rg etful nes s, error
13%
Rel yi ng upo n othe rs w ith ou t sufficient c o ntrol
9%
Ob ject iv ely un kn own s it uation Imp reci se definition of res po n si b ili ti es
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Cho ice of bad quality
1°/.
Oth er
3%
1%
ODES YOUR COMPANY HAVE A STRUCTURED AND DOCUMENTED 'INTEGRITY' TRAINING PROGRAM?
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Reason for Training: Business 'INTELLECTUAL CA PITA L' :J The market value of a perso n(s) is a combi nation of the knowledge the G
person creates and owns A company's worth is an accumulation of its emp loyee's knowledge.
II
D The market val ue of a comp any is determined . in a large part, by the intellectual capital , as perce ived by the inve sting public
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1:1 Exxon 's intellectu al capital estimated to be 72% of its market value.
c Coca Cola 's is estimated to be 96%
LOSS OF CAP ITA L n
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,_ __
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Intellectua l capital of the oil and gas business continues to "leak into othe r ind ustries at an alarming rate "
D In the UK , across all industries. 25 ,000 engineers retire annua lly and on ly 12,000 graduates replace them CO MPANY RESTR UCTURINGfRE ORGAN ISA TION
As we 'downsize' , we are forc ing staff , with critical knowledge and co rporate memory , to
:::J The industry is contin uing to make mistakes .
leave, and com panies leam too late that such knowledge is irreplace able. 0_
.... _ '
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Reason for Training: Staff n
A USA survey by The Gallup Organization concluded : o Employer -sponsored training and education is a major attraction for young staff looking for jobs. Q Worker s say they are more likely to remain with companies that invest in training programs .
.:J A survey by the American Management Assoc iation concluded: :J Investing in employees skills through training is a more effectiv e tool for retaining staff than purely financial incentives.
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Reason f o r Training: We are old••• CJ W e are an old wor kforce! o Average age in oil and gas indu stry is 49 1:1 a 'young' worker being 43 and
u an 'old' worker being 55 o Early retirement is still popular :J Could lose ha lf of our experienced work force by 2007 :J 50% of She ll's E&P workforce will retire ove r the next
12 yea rs" n In one major contractor the average age of senior staff is
now 49 years and increasing by about one o
yea ",r~;~n~e~v~e~ry L
---,
25 ~
tNo. OU f age profile should be this, but..
20 l' III 15
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20
45
65
Reason for Training: We are old.•• o The effe ct of age demographi cs is 'tighter' intell ectu al capital in com pa nies o We need to preserve 15 and grow our intellectual l' ~ 10 capital
:J This can be partly
U- - - - - - -I U- - - - -
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achi eved by having 5 well-trained staff, under continuous and I accelerated 0.... develo pment .~ ~ program s
O _ L l < I 2007
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e:: 20· 25· 30- 35- 40· 45· 50- 55- 60- 65+ 24 29 34 39 44 49 54 59 64 ag e of staff
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Reason for Training: The Future .:1 This cent ury ..
u OUf limitations will not be computers and communication capabilities (they will rapidl y advance ), but rather. .. a O Uf limitations will be learning , experience, values and information.
be how oil and gas companies will succeed in our industry in the future.
:J These will
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Reason for Training: Regulatory n The USA Pipeline Safety Regulations Federal Reg ister Part 49 CFR §192.763 . Pipeli ne integrity managem ent in high consequence areas state:
V NIHO STATU OEPAR TM ENT
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TRAN SPOR TAT IO N
:J (2) Trai ning (i) Supervisory u An operator's integrity management program must provide that each supervisor... has appropriate training or experience in the area for which the person is responsib le ... :J (2) Tra ining (ii) Persons who eval uate.
o An operator's integrity management program must provide criteria for the qualification of persons who review or analyze results from integrity assessments and evaluations..
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What is Pipeline Integrity? o Pipeline integrity is the proc ess of ensuring that a pipeline is safe and secure . It involves all aspects of pipel ine design , operation, inspection , maintenance and managem ent.
LI This presents an operator with a
complex 'j i g s aw'to solve if they are to maintain high integr ity.
o Pipeline integrity management is the management of all the ele me nts of this com plex jigsaw .
Risk .. nd Rel ia bility
o The management brings all these pieces of the ji gsaw together.
What is Pipeline Integrity?
o
The USA's DOT considers .. .. ::J The term "integrity" means that a pipeline system mainta ins its
structural integrity and does not lea k or rup ture. IJ "Integr ity management" encompasses the many activities pipelin e
operato rs mus t undertake 10 ensure that releases do not occ ur, ::t lntegrity' will have different meanings in differen t sectors of the petroleum business ; for example: arc a customer, it may mean 'billable quality' of product; nrc a control room it may mean 'operational stability'.
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Pipelines Fail - Why? o
Pipelines carry hazardous products.
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The products are hazardous, not the pipelines.
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A pipeline will have high rel iability if it is correctly designed, maintained and operated. Pipelines can fai l due to: i. natural diaste rs. ii. gross human error, iii. sabotage/wars
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iv. existing defects in a new pipeline, or
v, defects introduced during operation n
Enginee rs can do little to preven t (i) to (iii).
Therefore , engineers maintain the safety of a pipeline by prevention, or elimination, of defects that can cause failure . () ~ . OspOn l td . 200 '
Important Notes
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Course Notes and Guidance, 1 Ll The defe ct assessment course and the notes ha ve been de....elop ed o ver many years Ll They are updated and imp ro ved after e very cou rse, based on: 1. course feedback, and 2, changes in the met hods reported in the literature ,
POAM THE PIPELI NE DEFECT ASSE SSMENT MANU AL
o The note s and recommended practices are conside red best industry practice, based on: :J the authors' experiences Q
industry practice around the world
"Q literature reviews and the Pipeline Defect
Assessment Man ua l, a joint industry project supported by 16 companies.
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Course Notes and Guidance, 2 o
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Your co mpany and your work will be lim ited by both company codes and practic es, and your nation al and state legislation and regu lations . o For example. we will recommend a dent is 'acceptable' under static loading, if it is less than 7 percent of the pipe diameter. o This is a technical limit, based on fitness for purpose. !'J You must always check other engineering aspects and the consequencesof your conclusion (e.q. a 7% dent may restrict product flow and pigs). n Your cooesneqrstauorvetc. may not allow such a deep dent. You MUST always chec k local and national limits and leg islation, before applying fitness for purpos e:
1. can I apply it, and 2. can I use the results? o _ uo2001
Course Notes and Guidance, 3 o
o 1.
n
2.
Fitness-for- Purpose in this course means that: a particular structure is con sider ed to be adequate for it s purpose, provided the conditions to reach f ailure are not reached (see 8$ 7910 or API 579) . Note that 'fitness- for-purpose' may have a legal and contractual meaning in your country: CONSULTANT'S OBLIGATION For example, in the UK, a consultant engineer is expected to exercise 'reasonable skill and care ' in their work. CONSTRUCTOR'S OBLIGATION
o However, a contracto r carrying out a construction has a fundamentally different obligation, they are obliged by law to warrant that the comp leted works will be fit for their intended purpose . o This will be implied in the contract ; it does not have to be staled explicitly
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Course Notes and Guidance, 3 (contd.) ::J Therefore, if a consultan t gives a warranty for fitness-for-purpose (on the
completed works) and they are not, they will be liable even if they have used all reasonable skill and care o The damages that can flow from a breach of warran ty are different from those of negligence : 1. Warra nty - you pay the costs of mak ing the works fit for purpose 2. Negli gence - you pay for anything that could have reasonab ly been foreseeable. o Therefore, check with your professional indemnity insurance o
What are you cover ed for as a com pany or professional? C1 Usually, professionals and consultants are NOT covered for warranties
Course Notes and Guidance, 4 :J We have to be careful with 'definitions'... :J
New standards (e.g. API 1163) now consider...
':J
a 'defect' as an anomaly" for which an analysis indicates that the pipe is approach ing failure as the nominal hoop stress approaches the specified minimum yield strength of the pipe material. This means an anoma ly with dimensio ns or characteristics that exceed acceptable limits
o an 'im perfect ion' as an anomaly in the pipe that will not result in pipe failure at pressures below those that produce nominal hoop stress equal to specified minimum yield strength of the pipe material. That means an anomaly with characteristics that do not exceed accep table limils.
c These definitions are consistent with API 5L definitions , c_
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Course Notes and Guidance, 5
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SAFETY is ALWAYS our prime consideration in any calculation rt It is YOUR RESPONSIBILITY to ensure that any fitness for purpose assessment is correct. Always understand the cause of any defect you're assess ing , o Try and use the bes t poss ible practices available, e Ch ec k calcul ation s, inputs and assumpions. !,;!
Use all relevant data, e.q . pig data , operations record s, ma ps, etc.
.:J Always appreciate the CONS EQUENCES of your assessment. !';J
If there is an error, e q. if the defec t measu rements are wrong , and the pipe line fails, what are the consequences?
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Consequences will dictate your safety margin on your ca lculations
:::J 'Rules of Thumb ' are fine , but limited to past experience , and remember
the origin of a 'Rule of Thumb' is ...
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ANY QUESTIONS BEFORE WE START?
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C _ 110 2001
Introduction to Pipel ine Design Penspen
Integrity
PIPELI NES DESIGN: Legislat ion .Pipe line l eg al/St at utory Positi on _ The ope ration of tran smission pipelines is usually con trolled by national regulations or laws. _ The selection of a design stand ard , or design calculations, are often limited by these regulalionsllaws. a t.aws ('statu tes') are created by Governments (e.g . the USA Cong ress). _ Regulations are 'rules ' based on an interpretation of these laws, usually written by Federal Departments. _ They are standards to implement. interpret, or make specific the law enfo rced or adminis tered . _ Regulations have the same effec t as Laws: both are enforceable. _ Failure to comply with either the laws or regul ations could result in lega l proceedings.
,
PIPELINES DESIGN: Legislation in USA & UK _ In the USA. the Department of Transportation issues a range of Pipeline Safety Regulations. e 'r hese Regulations rely heavily on the A$ME 83 1 stand ard s. _ Any pipeline design in the USA would be to ASME 83 1, and additionally satisfy these Regulation s. _ In the UK , the Pipelines Safety Regulations cover all transmission (of 'hazard ous fluids' ) pipelines in the UK . e 'Tbese Regulations are not prescr iptive, but goal setting but Regulators would expect existing standards to be the starting point of any pipeline design .
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PIPELINE DESIGN: We use 'Standards' _A pipeline owner will expect a designer to produce a pipeline to a recognised pipeline standard.
_U sually, there will be a recognised (by both the pipeline owner & the regulator y au thority) standard alrea dy in use in the cou ntry where the pipeli ne is 10 ope rate .
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PIPELI NE DESIGN: Fundamental Issues . Any pipeline standard used must address four key issu es:
Safety - the syst em mu st pose an acceptably low risk to the surrounding population/environme nt Security of Supply - the system must deliver its product in a constant manner to satisfy the owners of the product (the 'shippe rs') and the shippers ' custom ers (the 'end users'), and have low risk of supply failure Regulatory & Legal comonmce- Some pipeline systems are regulated, and all pipelines must satisfy all legal require ments
Cost Effectiveness - the system must de live r the product at an attractive mark et price, and mini mise risk of losing business
PIPELINE DESIGN: Fundamental Elements
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Pipeline design includes:
•
condu ct eng ineering economic ana lysis and a m arket ana ly sis to determin e the optim um
system based on designs.
•
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se lect route,
" Route
ne through put & I • determi veloc ity , and pipe diameter
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Satisfy ,~ e9 11 l a tJ 0t'l5>fLaws
I
Se l'ecr~'h~'sign Standa rd/Code
Permits
ca lcu late pressure gradient, se lect of pumps/ compressors/other equipme nt,
' conceptual' design or 'FEED'
.J)e~lkld DeiStgi1 & Route
Construct and test dete rm ine pip e th ickn ess and grade , _NB - A pipeline code is not a complete guide to a good design. A design might meet a code requirements, but it may be a I:>P..,.".., 2006 Ro,&'1 unnecessarily costly,dangerous to construct, or ugly
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PIPELINE DESIGN: The First Standards••• _ Steel Pipel ine Des ign Standards were originally developed in the USA _ T he first oil and gas piperine stand ards were: _ ASMElANSI 8 31.4 Liqu id Petroleum Transportation _ ASME/ANSt 83 1.8 Gas Transmission & Distribution Pipe line System
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GAS TRANSMISSION AND DISTRIBUTION PIPING SYSTEMS
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PIPELINE DESIGN: History of Standards and Regulations _ Gas: ASM E 831 .8 was first developed in 1955. _ In 1955, industry/cod e concerns were main taini ng the safety of the pipeline system while economically trans porting natural gas.
• Liquid : ASME 831. 4 was first published in 1955. _ The primary purpose of the standard wa s to esta blish requirements for safe design . construction, inspection, testing, ope ration and
maintenance of liquid pipeline systems _ ASME 831 wa s quoted in the USA Pipeline Safety Regul ation s, first issued in late 1960s
0 0 0
1955
) b 31.8
1955
) B31.4
1969
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PIPELINE DESIGN: ASME standards were popular ••• _ As oil & gas was di scovered aro und the world , coun tries developed their own standa rds , bu t used ASME as a 'good pract ice' bas is :
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_ ego the fi rst ed ition of CSA Stan da rd 2183, 'Oi l Pipe Line Tran sportation', was pub lished in Ca nada in 1967, and in 1968, CSA Z184 , 'Gas Transm ission & Distribution Piping Systems', was published . _Most developed nations have their own standards/gu idelines, e .g . the UK uses BSI PO 80 10, Netherl ands uses NEN 3650 .
851
_ New internationa l (ISO) and European ('EN') standard s are ava ilable : _ ISO 13623 - stan da rd cove ring oil and ga s lines
_ EN 1594 and EN 14161 (equivalentlo ISO 13623) for gas an d liqui d lines.
PIPELINE DESIGN: Key ASME standards _ A S M E has 500+ cod es a nd stand a rds . _ H e re are some pipe lin e sta ndards : _ A SME 83 1.3:
Process Pip ing
_ A SME 831.4:
Liquid Petroleum Transportation
_ ASME 831.8:
Gas Transm ission & Distribution Pipe line System
_A SME 8 31 .8S: Managing System Integ rity of Gas Lines _ A SME 831 .11: Slurry Trans portation Piping Sy stem s _ A SME 8 3 1.12: Hydrogen Pipe lines and Pip ing (in deve lopment, due 2007) Remaining Strength of Cor rod ed Pipe lines _ A SME 831Q:
Qua lification of Pipeline Operato rs (under deve lopment) 10
PIPELINE DESIGN: Standa rds for Offshore Lines _ Most standards cove r both onshore and offshore lines _ ONV as Fl 0 1 is specifically for offshore lines, and is beco ming the most popular offshore design standard
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PIPELINE DESIGN: The 'Hydrotest' _ Our Design Standards give a variety of guidance. _ For exampl e, before we put a pipeline into service. desi gn standards require that we first ' hydrat est ' it
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_ This mea ns we fill it with water and pressu rise this water, to give a hoop stress/pressure in the pipe line of about:
• 90-1000/0SMYS , or
Hydrotest 0= 90-100% SMYS
. 1.1-1.5 x design pressure . _ W hen the pipeline pass es this test , it 'proves' the strength of the pipeline before it enters service _ We then fill it with product and it enters service.
Product
PIPELINE DESIGN: Oil & Gas Standards Differ . Pipeline standards treat oil and gas pipelines differently: _ For oil pipelines: a no account is taken of population density in their location (but note new movement in USA) _ there is no spec ified limit on density of (occupi ed) buildi ngs around the pipeline . you can generally build an oi l pipeline with a high stress ('des ign factor' (0.72) in most locations)
_ For gas pipelines: a account is taken of population (building) density _ minimum dista nce from buildings may be speci fied _ Stress ('design faclor' is lowered in popul ated areas (design factor is 0.3 in UK, 0.4 in USA ) _ gas pipe line standards limit popu lation by 'location classifications'
PIPELINE DESIGN: 'Right of Way" _Our pipeline is laid in a 'right of way' (ROW) _The pipeline owner usually leases this land _The ROW is usually about 8 to 50m wide containing the pipeline. _The ROW is kept clear to allow the pipeline to be safely operated, aerially surveyed and maintained. _ Pipeline com panies are responsible for maintaining their rights-of-way to protect the public and environment
CI ............ 2IlOII ......'
PIPELINE DESIGN: ' Ri g h t of Way' _ The pi pelin e operato r retains access rights for the ROW for the life of the pipel ine . Thi s : e enabtes wo rkers to gain access for inspection, maintenance, te sting or emergencies _ maintains an uno bstructed view for freq uent aerial surveillan ce _ identifies an area that res tricts certain activities to protect the landowner, the community, and the pipelin e itself.
- .. ROW
:~ . . .: .. ,
"
PIPELINE DESIGN: 'Working W idth' _ We will temporarily need a larger width that the right of way, 10 allow us to construct our pipeline _This is our 'working width '
I
•
In the USA . the Offi ce of Pipeline Safety has no authority over land use practices outside of the pipeline rig htsof-way.
PIPELINE DESIGN: 'Boundaries' for a gas line CLASS 1
'Locat ion classification' for as lines
Wo rking width
~ ill
~ ill
220 yards
~ ill
~ ill
~ ill
220 yards
1 mile coPeospeo 2006 Rev6! 1
PIPELINE DESIGN: Location Classification No restriction In this zone
Limil building in this zone Prevent, or severely limit, ROW -
no building allowed here
ROW
Prevent, or severely limit, " ..",..""..",.""..."".."..p.l!l!rJ.JngJ'1 ,(fJf~"~Q(JfiJ ,, .. Limit building in this zone No restriction In this
zonca
PI PELINE DESIGN: ' L o c a tion Classification' i n ASME CLASS 1: 10 or less living units. CLA SS 2 : >10 & <46 . CLASS 3: >46
220 yards
ClASS 1
220 yards
I
1 mile
'Living units'
Pipelines in Class 1 location can operate at high design factors. Classes 2·4 operate at lower design factors than Class 1.
ts
PIPELINE DESIGN: ' L o c a t i on Classification' i n ASME AREA
CLASSIFICATION
Class 1 (Oiv 1) Class 1 (Oiv 2)
0-10 bu ild ings (r ural)
Class 2
11-45 bu ild ing s (areas aro un d towns )
Class 3
46+ dwellings (e.g. s u bu rban), etc ".
Class 4
MUlt i-storey-type buildings
e r nese locations Originate In work In 1955. Aena l photographs of exrstmq pipelines and th eir surrounding buildings were ana lysed and 4 location ctasses were established that close ly resembled current practices in the design of pipelines . • Originally, a 'cornoo r wio th' of 0 .5 mile wide , with the pipe line at the centre (this figure was the same as the width of aerial photographs at that time .. .), was used to determine the population density at risk. _ 0.25 mile was later introduced by OPS as mo re appropriate (as it did not affect safety to people' or risk to pipeline): therefore, t he location class is defined by an area that extends 220 ya rds on either side of the center line of any contin uous t -mne length of pipeline. .. .._ _ ._...-.....- ............
.•• . - _ _ ,_ ....._
.. .. 0...,
PIPELINE DESIGN: Location Classification in USA••• during operat ion ClASSIFICAnON
No. of buildings -N_ Construction
Class 1 (Oiv 1)
Class 1 (Div 2)
0-' 0
11-25
Pf
OWlolAOP bill nol gr..-tt>an IlO'lIo SUYS
11-25
~1,Uo()P
26-45
(l
8 _ pr-... but not ~ ""'" 7Z"fo s""'s
(I
61.-1'fftOU'e but not ~_ ~ 60"4 SMYS
' 6-05 IolIA-SlOIy ~
UoIIi.slOry ~
. _
.... _
... _
• .\SWE8J1 . ~_ _ . ..... _ _
_ -s\Ory~
46. _
... _ _. . . - _ , . ,..... "\1
.,.. _"'...,,_.....-.
__
. n_ _
_
_ '"lI .. _
...-
__
_
_
72'1lo SMYS
1I.SS_ _ bu1 _V-lI>an
067_ _ _ bul ...
66'
Class 3 & 4
not~~
~
SMY5
" ' - WAOP 1M noI grNIoW hn 6O"Jlo SINS
,6-<>5
11-4 5
buI
II 67_ P'ft*" buI no! gnNI* lI>an 60'4 SUYS
66'
Class 2
Max imum Allowable Operating Press ure
No. of bultdings -Operation
__
....
""" ,.."""
~
.....
""'
o S6-..c pan 5O'Il. SMY S _ _ bill
noll
....... " . ,
""
~ --.g ~....,_. --r_ _ ....._ _ _ ..~ _ ........ _ "' ... _ .. • _ _ .. - - .
21
PIPELINE DESIGN : Liquid Lines Location (USA Regs) No pipeline may be loca ted within 15 metre s of any building s or places of public assembly unless it is provided with alleast 305 m m of cove r, in addition 10' L. ocat io n
COVF.R* Norma l exc avat ion in(mm)
For rock excava tion
Industrial, commercial, arc residential areas
36 (914)
30(762)
Walet Crossings
48 (1219)
18 (457)
Drainage ditches
36 (91 4)
36 (91 4)
Deepwater port sa fety zone
48 (1219)
24 (610)
Gulf of MeKico, and offshore (less than (3.7 m) deep)
36 (914)
18 (457)
Any other area
30 (762)
18 (457)
O ~ 2OOa _ '
_ ......-IIJ,. .... l PG _ _ ....
.... - . ..... _ " ' _
e-... ....._ .....
. Pi peline must be at least 12" from other underg round struc tures _ Pipeline componen ts can be ab ove ground, if (e.g.): _ Areas under the direct co ntrol of the opera tor _ Area is inaccessibl e to the public. 22
PIPELINE DESIGN: Liquid Lines and
'S a fe ty Zone'? * _ Research conducted in the USA during the 19805 on liqu ids pipelines show ed th at:
_T wo third s of deaths and damage, and three-fourths of inj uries occurred within 150 feet of the point of discharge ;
_ 8 percent of death s, none of the injuries . and 6 percent of property damage extended as far as 1.2 mile from the pipel ine
°rRB '!lea
~ROW'!l'~ P_._~S¥o fl'
lWt>o9oP
_ _.. '-ono-...c.:....o, ..._"""""oc
23
_~............,..
PIPELINE DESIGN: Location Classification fo r offshore lines? _ Offshore pipeline codes do not have 'location classifications' as these pipelines ar e not usua lly near bui ldings , other than oil and gas facilities _ Sui whe n a pip eline app roaches the sh ore line , an d the re are occupied ----.. bu ildi ngs at the shorelin e, then the loca tion classifications are applied _ A lso, the contents of an offshore pipe line will affect the safety/risk evaluat ion of the pipelin e at the design stage (e, g as PD 80 10-2) . Finally, offshore design code s red uce de sign factors at pipe lin e ris ers
0 __
2OOIl~' 1
Shoreline . ._ ~ ~
...
PIPELINE DESIGN: Design Stresses •
We want to ensure that our pipeline does not fail due 10: • Burst • Structural collapse (buckling) • Fatigue
•
• Fracture And we don't want our pipeline to become 'unserviceable' due to: • Ovalisation
•
• Displacements Therefore, we control our stresses below a specified stress level or ... • a 'design level' or 'design factor' . These factors vary in codes.
·A 30" pipeline with an internal pressure of 15 MPa is loaded by a tota l fo rce of 1.1 MN (1,100 lannes) -This force tries to separate each metre length of line, so that each metre of wall has to carry a hoop force of 5.5 MN.
PIPELINE DESIGN: Key Parameters in Standards••• Pressure, Stress, Design Factor
.Pressure (p) in a pipeline causes a 'hoop' stress in the pipe wall. The higher the pressure the higher the hoop stress. .Pipeline design codes limit the level of hoop stress in a pipeline using 'design factors'. This will effect D and t.
Pressure
F'o"'"
Hoop stress
\
. 'Design factor' is:
hoop stress/SMYS
\
Design Factor
=Hoop stress SMYS
_Hence, the higher the design fac tor, the higher the stress in a pipeline.
r
II:I p"""",", ]006 R. .6/ 1
26
PIPELINE DESIGN: Pressure to Stress _ When we put pressure into a pipeline. the pipe wa ll experiences a load or a 'force' thai attempts to expand the pipe _ T he 'force ' is fro m the pressu re in the pipe .
=
• Stress Force/Area . 'Area' is a function of Diam eter and Wall Th ickn ess
_ The internal pressure causes a 'hoop' stress . _ The higher the pressure the higher the hoo p stress.
,
./~~ """"""""'"
~
".
•.....
...,.•.•....•..•.•/ . /
-:
../\ ~ &&
'.;
,""
/ ..../
...•••.,••.•••
(
Interna »:" press ure
c _ _ """"_.
PIPELINE DESIGN: Hoop Stress
. The hoop stress tries to expand the circumference of the pipe in the 'hoop' direction
"-'-. /
.'
'
.. ' .,-
-",
.
"'
··
hoop stress •••••••••••••.»
hOOp stress
za
PIPELINE DESIGN: Calculating 'Design' Hoop Stress
- '-r - - - - - - - - , -
,
,It
The hoop stress is calculated by:
pD o
2t (Yo hoop stress - '-'---------~
p
internal pressure
o
diameter
(use outside diam. /0 be conservative)
wall thickness
hoop
29
PIPELINE DESIGN: Hoop Stress to Design Factor _U su ally the most important stres s we nee d to ca lcu late is the hoop stress . • Hoop Stress,
CT~:::
PD!2.t
.Pipeline design codes limit th e level of hoop stress in a pipeline - hen ce the co de s limit the pressure and size of pipeline.
hoop
• Pipeline design codes refer to 'de sign
factors'. _ This design factor is hoop stress/SMYS _ Hence, the higher the design factor, the higher the stress and pressu re in a pipeline.
Design Factor (9)= Hoop stress SMYS
30
PIPELINE DESIGN: Stress & Design Factor
Hoop Stress = ao = pDcode < ¢SAfYS < 'I'dxr y
».:
(}" =
stress. ¢; = de sign factor,
8 = hoop, t = wa ll thic kness.
D = diameter, p
= internal pressure,
OJ. = yield strength,
Design Factor = Hoop stres s SMY S
code = as specified in the code _ Usually, codes use outside diameter, a c ooee can use either nom inal or minim um wallthickness _ Minimum wall is typic ally -8% nomi nal wall in welde d line pipe. _ The high est design factors (0.8) are in the USA and Canada. Most other codes have 0.72 as highest design factor
"
DESIGN FACTOR: Is a Safety Factor a r here are uncertainties in the design, construction, operation a c c nsequenuy desi gners use 'sa fely factors' in their calculation s
_ The Design Factor is the inverse of 'safety factor' , It allows Ior": . Variability in materials.
_Variability in construction practices Design Factor = 1/S afety Factor a u ncertaintres in loading conditions e u ncertamnes in in-service conditions _ W hen we can not 'prove' the condition of a new stru cture we have a low design factor (high safety factor ): _bridges, ships have a design factor -0.6. _if the structure may buckle, we'll reduce this to -0.5. _ If we can 'prove' the structure prior to service, or if we have high ' red undancy ' in the structure, we can tolerate higher des ign factor s _ We can proof test pipelines, therefore we have higher design factors.
)
__
.....'."""'._,_ _"'C.,_...... """
..... ,_ Tn..- ' - _ _ ~ ""'T"" .~_
~ _ " _ r
.... _ . . " .
Water
az
DESIGN FACTOR: Is a Safety Factor _ W hen decid ing on a safety factor we need to consider ma ny details, for example " Safety Factor
Appl ication?
1.25 to 2 0
We are confident about ma terials and load s ... we are going to perform regu lar maintenance and inspection... we have condu cted a proof load ... .
2.0 to 2.5
As above, but no proof load
2.510 3
Less-tried materials , perhap s brittle , under 'average' loadings ...
>3
Untried materials, unce rtain environm ent s. uncertai n loads, etc.
_ We need to increase our safety factor further If the consequence of failu re is high . e.g. cas ualties II the teeter of safety is too big. performance/cost are an tssues! If the factor of safety is too sma ll, sa fely is an issue!
PIPELINE DESIGN: 'Design Factor' and ' L o c a t i o n Class' i n ASME B31.8 ASME
AREA
CLASSIFICATION Class 1 {Div 1) Cla ss 1 (Div 2)
Maximum Desig n Faetor (hoop stress/SMYS) 0.80
0·10 bu ilding s (rur al)
0.72
0.60
Class 2
11-45 b uildin gs (areas arou nd towns)
Class 3
46+ dwelling s (e.g. suburban), etc';
0.50
Class 4
Mu lti-sto rey·typ e building s
0.40
_ There will be high numbers of activities in the higher class areas (Classes 2-4) , because there are more buildings (people) in these classes . Most design standa rds require reduced design factors in these high location classes e o peretors usually cannot reduce pressure; therefore, operators maintain the pressure and diameter, and increase wall thickness . Increasing wall thickness ensures more resistance to external interference
o-..-au_,
33
DESIGN FACTOR: Wall thickness Size (inches)
Type of
Tolerance (% Specifi ed Wall Thickness
pipe
Grade B or lower
Grade X42 or higher
<2.875
All
+20, -12.5
+15 , - 12.5
>2.8 75 and <20
All
+15, -12 .5
+15 , -12 .5
>20
Welded
+17 .5, - 12.5
+19.5, -8
>20
Seam less
+15, - 12.5
+17.5, - 10
I-
ASME Stalldards use 'specifi ed ' wall thickn ess when calculating design factor : some othe r standards use mimmum 35
"
MAXIMUM DESIGN FACTORS (HOOP): International Comparison Hoop stress (0"1/) equauoncu
STANDARD
Hoop Stress Design Factor
Hoop Stre ss Design Factor
(u sing t~ode)
(using t nom)
AS ME 831.4
uo=PD/ 2tnom
0.72
0.72
AsM E 831.8
0.80
0.80
858010-1
O"e=P D12toom utrP D12tJtlltl
O.72l1 )
0.65
CsAZ662
uq==PDl2t nom
0.80
0.80
AS 2885 .1
utT'P D12tnom
0.72(2)
0.72
ISO CD 13623
a'=p(D-t)l2t~
0 .77 to 0.83
0.76
EN 1594
a q=pDI2t"""
0.72
0.65
__..
.
~
,
_
~
_
~
_
-
.
.
.
,
.
.
" _._"'.... _,_ ..._-_.,,,,--' _ _. . . -. "' ,, ·. . • •.
_. _ _
~< - , - ':., . -
,
_--..-~
EN-E_an.
·
_._--
....,. -..-.,._-..... -.... _ - ' -..,' ... _"' ..
loS _ Austra ha
,
CSA_ 150 CClI'acIa __
BS_ UI( .
,
""" -""
·_
_
'"v ..... _
_
, _.....
J6
DESIGN HOOP STRESS: Offshore Examples _Offshore pipeline codes have various equations and conditions for calculating hoop stress . _For example , DNV
as
F101 uses:
_Hoop stress = (pi - Po)(D - tnom)/2tnom
6 0
pD =- 2t
.where t nom is t he nominal wall thickness less fab ricatio n to lerance, less any corrosion allowa nce , p is intern al pr essu re and Po is exte rnal press ure
Po
_The international pipeline standard , ISO 13623 uses a similar formula: .Hoop stress = {pi - Po)(D - tmin )f2tmin ewhere t", n is minimum wallthickness which will incl ude fabricat ion to leranc es and any cor rosio n allowa nce
DESIGN HOOP STRESS: Offshore Codes ('Usage') Design Factor*
STANDARD
Risers
Line pipe
DNV
0.5
0.72
ASME 631.4
05
0.72
ASME 631.8
0.6
0.72
6S PD 8010-2
0.6
0.72
~,
~( )
-.. . .~ ?\.
Design Factor - Hoop stress SMYS C'
(
p.""",":1006Rw4&" • The 'usage' (design) facto rs are the same, but the code s have different definit ions of I m e and l oom
38
DESIGN FACTOR: W hy '0.7 2' in most standards? 0.72
0.72 = Design Factor = Hoop stress SMYS
39
DESIGN FACTOR: Why ' 0 .7 2'1 _ Most pip elines around the world have a maximum design facto r of 0.72 , although the re are some pipeline s operating at higher factors. _ This 0.72 design rector originates in North America , from lheAmerican Pipeline Standard ASME 831 .
_ The 72% SMYS limit originates from the 19305 in the USA . It was based on the mill testing of tine pipe _ The mill (water ) test was typically 90% SMY$. e o oerators agreed that a 1.25 safety factor on this was reasonable, therefore the 72% SMYS limit was created, and appeared in the American Code ASM E 8 31.8 in the 196Os .
_ It has no stru ctural significance _ It is an historica l limit.
0.72 = Design Factor
= Hoo p stress SMYS 90% SMYS
0
-=:i. ~ 90% SMY$/l.25 72% SMYS
=
DESIGN FACTOR: 1935••• '0 .7 2 ' _ T he first '0. 72' design factor pipeline was the Natural Gas Pipeline Company of America in the 1930s: thought to be the world 's first all electric girth welded pipeline . This was needed as no oth er all welded pipeline had been put in use, so the 80 % of the manufact urer's m ill lest (typically 90% SMYS) was introduced. _ A 72% stress level first app eared in the 1935 Am erican Tentative Standar d Cod e for Pressure Pipi ng . _ This is the fir st record of using a pressure te st to set maxim um operating pressur e/stress , and the pressure tes t is still used to day to set m aximu m pre ssure, altho ugh the fie ld test is used today. _ But note ... the line pipe standar d in use in 1935 (API 5L ) did not require hne pipe to be tested to this 90% SMYS; for example . Grade B line pipe (SMYS of 35,000 Ibfl in2 ) was required to be tested between 16.000 and 18.0001bflin2 (about 50% SMYS)
"
DESIGN FACTOR: Why '0.72'1 _ Another explanat ion of '0.72 ' is: _ The 90% SMYS mill tes t..
a was reduced by 12 .5% to allow for tole rances (under-thickness') in the line pipe wall thickness .. . _ And then divided by 1.1 to allow for 110% overpressure allowance (as was common pra ctice in the water industry) _ 90% SMYS x 0.875/1.1 0 .72 SMYS
90% SMYS
I ' 0%,
I
=
II
,
'--..-
t ' 0 .72 SMYS
DESIGN FACTOR: Why 0.8 i n some standards? _ The 0.72 design facto r was based on a safety margin of 1.25 on a wate r test in the pipe mill to 90% SMYS . • Using the same log ic (i.e. a safety factor of 1.25) , pipelines hydrotesled in the field pre-s ervice to 100% SMYS would be able to operate at 80% SM YS.
_I n the 19805, the ASME 8 31 .8 committe e considered >72% SMYS pipelines, and a 1990 addenda to the 1989 ASME 8 31.8 Editi on included provi sions for the operation of pipelines up 10 80% SMYS.
_
_
\
) 0.72
0 .72
= Design
.~ ) Factor
=90% SMYS (mill test )
0.8
\ ~
0.80 - Design Factor = 100% SMYS (field le st)
1.25
1.25
C_2OCIi"-"6;'
"
DESIGN FACTOR: Why are USA lines still limited to 0.72? s u s Reg ulations restrict the maxi mum des ign factor in oil and gas lines to 72% SMY S. _ This restriction was a prob lem for some lines: some wer e ope rating> 72% , and in som e cases 80% SMYS , when they cam e into force , . 'Grandfather' lines (old lines operating above code) were given concessions to operate - in some cases - up to 85% SMYS AS ME allows 0 .8
C _1OOIl Ra.ll. ,
USA Regs
=0 .72
'Grandfather' >0.72
Introduction to Oil and Gas, & Pipel ines We must under stan d bas ic pipeline co ncep ts before we understa nd defect beh avio ur
_Outline of this lecture : eon, Gas, Energy .Pipelines - History, Economics
~.,P~n
• • e ft Ud. 200T
1
n \tI D
EN ERGY: Where does it come from? •
The Sun provides 99.8 percent of the energy input to the earth's surface, but: • there are ove r 1 mi llion tonnes of oil cons umed every ho ur arou nd the wor ld' , an d • 250 mi llion cu metres of gas are consumed every hou r around the world • USA cons umes 20 mi llion barrels (360,000 ,000 gallons) of oil per day! • Wo rld energy consump tion wi ll inc reas e by 2%/annum from 2003 to 2030 '
World Use of Primary Fuels is *: Oil = 34% Coa l = 24% Gas = 21% Nuclear = 7% Hydro = 2% 'Other' = 12%
World Supply of Primary Fuels is : Gas - 60 years Coal - 200 yea rs Oil - 40 yea rs (all proven and recoverab le)
2
.[ t>. 0.,. _ 2003 ·AJ· _
w co'""",,", 0,
o.r>d u_•. o.>:du(""'il.'&ct" C'1y"" ",,>oo,' g "' •• n.'flI "'""" "' '"' ...'OCO"e" I ,;.,.
"'9""""" •• OCOnQ Iy
THE PETROLEUM INDUSTRY, Modern History . 1859: 2 oil wells in the USA, with value of 540,000 produced 2.000 barrels of crude oil. . Now, in the USA alone. billions of barre ls of oil are produced, with a value of $bill ions. _ The first co mmercially successful wells were in Pennsylvania . _ The first well was drilled to 59.5 feel.
,
--.- -
~
THE PETROLEUM INDUSTRY, Modern History _ W ithin 50 years of the oil indu stry's birth , petroleum had revolution ised travel by powering the world 's first airplane (1903) and helpin g the age of the autom obile . a ou consumption increased, with prices more than dou bling from 19 10 to 1920, as the number of cars and trucks on Ame rican roads grew from <500,000 10 >9 mi llion.
PETROLEUM: What is it? . 'Petroleum' is a complex mixtur e of 'hydrocarbons' _ Hydrocarbons are ma de up of hydrogen & carbon
e p en oiocm occ urs in the earth in liquid (crude oil), gas eous (natural gas), or solid (bitumen) form s. _ The term is usua lly restricted 10the liquid form _ But as a tech nical term it also includes gas , and the visco us or solid form known as 'bitumen' . Petroleum' is also call ed 'oil'. _ Oil in the ground is call ed 'crude' oil _ It was formed millions of years ago, from the effects of heat and temp erature on dead, anci ent sea life and plants (fos sils') Downstr eam' . Refers to refining, market ing. supply and transportation operations. Upstream · Refers to exploration, production , natural gas and gas products.
.... .
~
...... "". . _-"'.". ........
_.""""""'-
5
'OIL': What is it? _ The liqui d (crude oil) and gaseous (natural gas) phases of petroleum constitute the most imp ortant of the prima ry fossil fuels _ Oil is a mineral oil of natural origin _ It is in underground reservoir s. _ It is a combi nation of: . Iiquids ('hydrocarbons'): . other liquids (e.g. water ); and
. gas es (e.g. 'natural gas') _ Oil som etimes naturally see ps to the Eart h's surface along fault lines and crack s in rocks, where it can contaminate wate r as bitumen (tar, asphalt ) deposits . Typic al USA crud e 011 has a carbo n content of 83 10 87%, a hyd rogen co ntent of 11 to 14%, and minor amounts of oxyge n, nitrogen, and sul ph ur
Bitumen
e
'CRUDE' OIL: What i s it? _ Oil in the ground is ca lled 'crude oil' _ It is oil that has not been proce ssed into 'products' such as qasotene. a c rude oil ranges in colour from almos t clear 10gree n, amber, brown or black . II may flow like water, or creep like molasses. a c ruoe quality is defined by its density and sulphur content. _ Density is gi ven in deg rees A PI (Ame rican Petroleum Institute): the higher numbe rs recresentuqhter oil s, and are ca lled 'light' cr udes l ow numbers are 'heavy' oils .
_ It is described as "sour" or "sweet' ?" depending on the presence (sour) or absence (sweet) of su lphur and other sul phur compounds . C_
Brent oil is light and swee t. Dubai oi l is heavy and sou r. Light, sweet oil is easier to refine. and prod uces greater QuantitIes of high value (e .g. ga soline ) products
UO :lOC'
CRUDE OIL: Refining _ ' Refining' is the process of converting a raw material (cr ude oil) into 'finished' products suitable for use by consumers. _ These products are gasoline (petrol), kerosene, gasoil (heating oil) , etc..
Refine ...
_ A typical large refinery costs Smillions to build and Smuhons more 10maintain and upgrade _ It runs every hour of the day, all year
--
.. Per..- l.I
Produ cts .•. CHJt 2001
8
OIL: What You Obtain From a Barrel of Crude Oil What Does A Barrel (42 gallons) Of Crude Oil Make? Gallons per barrel
Product gasoline
distillate f ue l oil
19.5 9.2
(Includes both home heating 011 and diesel fuel)
ke rosen e-type jet fue l residu al f ue l cu
4.1 2.3
(Heavy oils used as fuels In Industry, marine transportation and for electric power generation)
l iquefi ed refinery gasses st ill gas
coke asphalt and road oil pe trochemica l feedst oc ks lubricants
kerose ne other
1.9 1.9 1.8 1.3 1.2 0.5 0.2 0.3
aWe measure oil by the 'barrel' as oil was or iginally transported in wooden barrels, aFigures are based on 1995 average yield5 for U.S. refineries. aOne barrel contains 42 US gallons of crude oil. (=35 imperial gallons '"
159 Iitres) aThe tota l vo lume of products made is 2.2
gallons greater than the original 42 gallons of crude oil. • This represents "processing gain ."
GAS: What is in 'N a t ura l Gas'? • Natural gas comprises gases, occurring underground, consisting mainly of methane(CH 4 ) . • Typica l natural gas is: • Hydrocarbons: • Methane: 70 to 98% • Ethane : 1 tolO% • Propane: trace to 5%, Butane : trace to 2%, Pentane: trace t01%, Hexane: trace to 0.5% , Heptane-: none to trace
• Non- Hydrocarbons: • Nitrogen: trace t015%, • Carbon dioxide: trace t01% , • Hydrogen sulphide: trace to occasionally
e PenSW' ltd . 2007
Ethane:
GAS: What is in 'S o ur' and 'Sweet' Natural Gas?
• Natural gas can contain hydrogen sulphide
Abou t 1/3 of Alberta (Can ada) Natural Gas is sour
• Sou r gas contai ns hydrogen sulphide, or sulphides and/or carbo n dioxi~ ~======~ • Sour is often defined as >1% H2S • Sour gas will usually need purifying
• Sweet gas is low (e.g.<1%) in hydrogen sulphide, sulphid es • The process of removing H25 from a gas is called 'sweetening' Typi cal 'm idco ntinent' USA natu ral gas has 88% me th an e, 5% et hane, 2% pr opane and 1% b utane
-.. .. ... \10< ..... _
..
· Definitions of 'sour' vary. -e.q . in Canada, 'sour' natural gas is gas containing more than 10 moles of hydrogen sulphide (H25 ) per kilomole or natural gas ; is sometimes expressed as 1 per cent H2S
__.. . __
tt
- - 1 . , . ~ -
.,.-.'0-••_ - ..... " " _
OIL AND GAS: Effect of CO 2 and H 2S ('Sweet' and
'Sour') on pipelines... • We can have 'sweet' corrosio n if we have carbon dioxide and water in our oil, product or gas . • We can have 'sour' corrosion if we have hydrogen sulphide and water in our oil, product or gas.
"
ENERGY: Supply and Demand OIL •
>60% of proven oil reserves a re in Middle East • -20% of these reserves are in Saudi Arabi a
•
Main oil prod uce rs and exporters are Saud i Arabi a , then Russia
-..
GAS •
80 % of proven gas reserv es lie in 10 countries • 40% of wor1d reserves are in CIS
• •
• 30% of world reserves are in Middle East Largest consumers of gas (34% of tota l) is C IS'
_...-
USA and West Europe collectively consume the most. but they col lectively r.::-.,--:-:--,.,.--,.,...--,"'"--:::----;- ---, Supply and demand locations differ. Therefore : only possess 11% of prov en rese rves i. We"11 need pipelines for transportation, ii . Economics & Politics will play big roles .. ..
O _ l l O 2001
-e-_
..
---._
d .... _
~ 'T"'-"' d
_
... ....... _
OIL: The Political Dimension Oil & W ars have bee n linked m any t imes: _ The Trojans us ed catapults to hurl flaming pitch , gathered from oil see ps, at Greek sh ips
e wm ston Churchill in 1911 controv ersially de cid ed that the British Navy sho uld change from (British co al) steam power to (Pe rsian) oil power to assure the cou ntry's mastery of the seas . 1990-9 1 Gu lf W ar . Etc ....
'Control energy and you control the nations ' Henry Kissinger
ENERGY - Oil Reserves are Increasing 1000 m illion barrels
120 0
•
15 Countries have oil supplies > 10 billion barrels":
•
100 0
"USA (22 billion) -ueaco (12) "Venezuela (78) "Norway (10)
R",.tWorld
I!l US A
••
S&C Amer i ca
D F .S o v .Un ion ~ . M _ E a ,. t----
800
-Russie (60)
-Cenede (180" ")
600
"Libya (30) "Nigen'a (24) ' Iraq (113) 'Iran (89) 'Kuwait (97) 'UAE (98) 'Saudi Arabia (261) "China (18) "Qatar (15)
400 200
o
1 9 73 -8 6
[I
~ 1 .,t
1 9 86-9 8
' F IA, XIO' I ,", lA
.•eo.... d. . """""" ""'" .-" '"""" ' '''''' ,
too ,200 2110 ' ''' ",",00 '. '003 ' "'''
THE PRICE OF OIL - Can be a Roller Coaster!
1999. _ In the UK North Sea. it costs $1113/barrel to develop existing fields.
25
Brent Crude (USA prices sligntly higher)
20
OPEC annoonce red uce<1oulput
_ New f iel d s now cost $10/ba rre l
,
(compa red to $2 0 in 1980),
15
10 1st Q
2nd Q
3rd Q
4th Q
Quarter in 1999
"u,.. . -,-' Wdi,.o< 0'f""'""' ''''''''''''' ,., I J' "","""'",- '""-."".",, ,, ,·"",m",,,.'''''',""m,,,,,,,," "","" •. ",,,,,,I '''''f_I hid , I
(.S
,~"" ,,,, ,,,r,,~, , ~ "",,, " .
_ The global aim is now to reduce to $8. • Petrobras (Brazil) are planning deepwater oil development at $6/barrel.
,~II-, ' ''',''' ''' . ",,, ,'0 ft - I
THE PRICE OF EXPLORATION AND DEVELOPMENT $4/barrel
Middle East Easy E&P, good size fields
Deepwater('mean' depths are 100m)
$8/barrel
Vast reserv oirs in deep water (>300m)
UK No rth Sea
8GI
$10-12/barrel
Shallow water fields are being dep leted. Large E&P costs Deep water : 1950 5m depth
There are various definitioosof'd" " pwate, ' The US Mineral Manageme nt Service s co nsiders 'deep" 10 be >400 m (13 121t), .s this dept h requires deepwa ter t",,~no logy and traditional fixed plall"""" begin to ooc<:>ma uneCOnOfTOC The largest ~ x e d platform IS~e lrs B ullwi~ k l e ) is in 1353ft of water in the Guff 01M". ico 'Ullrade ep' lS now (200 1) generally cons idered >5000 ft ofw3ter
1970
100m
1990
686m
1994
1QOOm
2004
2300m H
Introduction to Pipelines
~C> I'e~.p.n ~
II !I t. \
Ltd. 2001
18
PIPELINES: The Start (1859 to 1879•••) The early oil rush Trans port by water
1
Transport by rail
',... ..,..""" O' S"""."'O" e-",,"f . ' ''' T."",'
Wooden stor ag e tanks
...... "IW'/ '''':heSl", "",'
19
PIPELINES: The Start...
19 15: Ca liforn ia . Shell Oil line
20
THE PETROLEUM INDUSTRY: Going Offshore _ The early years of the petroleum business was ons hore-ba sed _ the oil was plentiful onshore. and the technology was not ava ilable to go 'offshore' . in the late 18005, engineer s in California erec led wh arfs to tap oil & ga s reserves close to shor e, but. ..
los Ange les od fl ~ l d . 1890 0.
Iwww con s"'. c a. ~ov)
_ the first oi l we ll str uctu res to be built in o pen water s we re in the Gulf of Mexico
!';on all coa5I '"
c._ <_
00"'"" mmo_ )
"
O _ U I : I 2OO'1'
THE PETROLEUM INDUSTRY: Going Offshore _Kerr-McGee Corporation drilled the first well from a fixed platform offshore out-ofsight of land in 1947 _ Srown and Root built the offshore pipe line _ 90% of the wo rld's offsho re structu res are in relatively sha llow wat ers - less than 75 metres deep
• But oil and gas is now being developed at 2000 metres
C"--,-,,, lOOT
_._-_.-... "
PIPELINES & LINE PIPE
2J
PIPELINES: What Are They Made From? _ Our pipeli nes are usually made from steel. _T he steel we use in pipelines is called 'line pipe' steel, as it is spec ifically made for pipeline purpos es. _ It is bought from a steel manufacturer. to a specification.
C> P _ _ l .. 200 1
-,-~" " ,,,, ,,
PIPELINES: What A re They Made From? - 99% of all gas pipelines in the USA are made from steel line pipe " .The most-used specification in the world is the American Petroleum Institute's 'API 5L' e we can also buy line pipe to European ('E N') or International ('ISO') standa rds
=::=
API5L 2S .l'.... ~ ........_"" , , _ .. l&\!AGoOoG'lDooo.
'9'»'
LINE PIPE: Types
_The three types of modern line pipe are: _ double submerged arc welded (DSAW). _ This type of line pipe contains eithe r: _ a longitudinal weld; and _ a spira l weld.
_ high frequency we lded (HFW). _ This line pipe has a longitudinal weld . _ There are two methods used: . high frequency induction (HFJ): and _ electric resistance welded (ERW) .
• seamless. _ This line pipe has no weld long its length . CP
([
w"" '
)
OZ Z) ()
)
LINE PIPE: Welded Line Pipe _ Our larger diameter pipelines are made by bending a steel plate or strip into a tub ular and welded the ends together
_ The plate is shaped CU' and '0' ) befor e welding
~
PLATE
vO 'U'
'0'
27
LINE PIPE: 'Expansion' and 'Mill Testing' _ Most large diameter line pipe is cold' expanded ('E') diametrically in the pipe mi ll.
_T he line pipe is strained to at least 0.3%, and usually 0.5-1.5%, to give an increased yield strength , and the correct diameter and roundness.
If th e line pipe is expanded ('E') and has been made from shapi ng plate (' U' and 'E') it is called 'UOE' 28
LINE PIPE: 'Expansion' a nd 'Mill Testing' _ Each leng th of line pipe is then subjected to a 'hydrostatic test': plugs are inserted into the end of each length, and the section of line pipe filled with water and pressurised up 10 a hoop stress of 90% SMYS for a short time (seconce'). _ This internal pressure and end
~c . J.~\
plugging will cau se a compressive axial stress and hence a biaxial stress state exists in the line pipe.
ax ial
hoop
").
_ If the line pipe section was made into a pressure vesse l, with the ends free to move, the tensi le axial stress = 50% the hoop stress . • API 5L spec ifies 5 to 10 seconds, depending on pipe
LINE PIPE: Mechanical properties _ The tensile testi ng of material gives us basic m echanical properties
_We generate a 'stress stra in' curve _ This is a graphical rep resentation of the materials basic m echan ical properti es Specimen
Ultimate stress
--- - - - - o_ - -~~
Proportional limit
'Elastic'
STRAIN
'Plastic' 30
LINE PIPE: Y ield strength , UTS Specimen _ We cut our spe cimens from ou r line pipe for mechanical testing ,
a s eamress pipe uses transverse speci mens , as seam less pipe is 'isotropic'. _ Small diam eter «80/.0 inch) we lded pipe use transverse and large diameter (<: 83,1.. inch) use longitudinal specim ens (See AP I 5L) .
The manufacturer w ill not test every section
Longitudinal
ot une pipe. For examples. 1 in 20 pipe s may be tes ted,
using one tensile test.
LINE PIPE: Measuring yield strength and UTS •
T he tensile prop erties of line pipe ar e m easured from specimens.
•
We load these specimens and plot the force (load) versus the spec imens elo ngation (strain ). W e measure: T_ I•
• the yield stre ngth; and
"""I
• the ultimate tensile strength (UT S)
T_ S ~ .
V>eld Sl'fftQIh
h
Load ~
--.-
,-
...... Yield
EKample stress-strain curve \ ~.
" _
..... 2001
---l
~
".
Elongallon
~ -- -_._-
32
LINE PIPE: 'SMYS' and 'SMUTS' •
The Pipe Manufactu rer ensures the strength of our pipe is above certain 'specified' minimum levels: • specified minimum yield strengths (SMYS) , and • spec ified minimum ultimate tensile strengths (SMUTS*)
.oo ,f:~:~: ~~~ -.-::~.- :-.-= tim8'te tensile s reoot
SMUTS ...
SMYS ~ ..~ Load
,!. ,;
-
..... Yield
Histori cally, SMY$ has been meas ured in 'old' units of Ibf/in2
200
Exam ple stre ss-strain curve
\ ~oo;-----------""-----~ 0.10 Elonga tion
· of 'SMT $'
LINE PIPE: 'SMYS' and 'SMUTS' •
Our actua l yield strength and tensile strength are usually above $MY$ and SMUTS ftimate tensile s reng Ii1
' 00 SMUTS
• ... .. ....... "
soc
SMYS
, Load
"a
...... Yield
zoo
!
"
' 00
Exam ple stress-strain curve
0 000
0.10 SI "' in
o P"" "",o lt a . 2007
Elongation
LINE PIPE: 'SMYS' and 'S M UTS' & Design Stresses •
Our design stresses (often quoted as a percent of the SMYS) are always well below the SMYS, to give us a safety margin. Ultimate tensi le strength SMUTS
SMYS Load
•.•.300..
~
-
YIeld Safety margin
200
j ~ -oo----~c---------,-~---\c-_.J
0:_""200'
We 'design' our structures in this region, but they "fail' in this region. at much higher stresses & strains This gives us a safely factor on both stress and strain
35
LINE PI PE: 'SMYS' and ' SM UT S' & Design Stresses The SMYS will be below the actua l yield strength in most pipeline spools
I 60.000
!
.....
~
""' ~ ~'"
Ibf/in 2
-
c::
.e>
'"
Ql
Q
,--
::!;;
CI)
~9 0," ~>-
~
:::l ::!;; CI)
'"""
§
H, o ~
~ "
J6
LINE PIPE: 'Grade'
•
•
•
API 5L specifies the requ ired yie ld strength of a pipel ine.
•
'Grade'
=
It is trad itionally measured in un its of Ibfli n<
We normally know line pipe by its 'grade'
SMYS (/1000 Ibfli n 2 )
•
Line pipe w ith an SMYS of 52,00 0 Ibf/in~ is known as gr ade X52.
•
60,000 Iblt in' is known as X60, etc.
Some lower 'grade' steels are known by letters (Grade B or A) •
These have SMYSs o f :$35,000 Ibll in' :i[~ lc.
Th is mat erial ha s yielded al->52,OOO Ibllin' .
70 60
Therefore it has an SMYS of 52,000 Ibllin' .
0
We will ca ll this line pipe
40 30
maler ial'X52"
20
--
I Ultimate tensile strength
Yield streng th
Failure
10
4
2
e
6
10
12
c·p",,_ , UO. 200 7 St ress Units : 1 h i
11lO0ps i
1000 1Win'
6 69 M P~
689 MNim' - 6 89 Ninm'
LINE PIPE: API 5L Grades, Strengths
APl5L
EN10208-2 and ISO 3183·2
Grade SMYS
SMTS
Nfmm2
N/mm2
241 289 317 358 386 413 448 482 551
413 413 434 455 489 517 530 565 620
B
X42 X46 X52 X56 X60 X65 X70 X80
Grade
SMYS
SMTS
N/mm 2
N/mm 2
L290
245 290
415 415
.
.
.
L360
360
460
.
.
.
L415 L450 L485 L555
415 450 485 555
520 535 570 625
L245
.'W e ooy om line
pipe from suppli ef",oOO ,pecity ils diame ler, woll Il l i c k ,, ~ss, and 'g rade' The g rade d ic1ales how sl rooglhe line pipe will be T il<) 'grad e' nurro!:>er, re1ers 10 Ihe yield WOflg1h of Ihe line p ipe in Ibfl in' . Fo r e .o ~ l o . 'X42' is lino pipn wi1h o specifiC'drninirr
'X' means
==_==__==---, 'SMTS' is specifred minimum tensil e strong lh.
r
hig~,
s ~reng t ~
38
LINE PIPE: Diameter and Wall Thickness _ We buy our line pipe from suppliers , and specify its diameter. wall thicknes s. and 'grade'. _ The diameter and wa ll th ick ne ss we need for o ur pipeline are determined duri ng its design , _ If we have large oil an d gas rese rves , at very high pressures, or if we want to transport large amounts of pr od uct. we will need large diameter line pipe .
_ If we are tra nsporting prod ucts al high pressures , we will ne ed th ick wa ll line pip e . to resis t the stresses ca used by the high pr essures .
w•• "_l.. 200'
thickn ess
PIPELINES: Are Coated on the Outside to Prevent Corrosion _Buried pipe is coaled to protect it from the surrounding envi ronment. _W e've been coa ting most of our pipes since the 19405
_A breakdown in the coating will result in pipeline metal being exposed. _Ttle materia l used for coa ling pipe s varied over the ye ars as tech nolog y evolved :
1940's and 50's
coa l tar, wax , and vinyl tape
1960's
asphalts were used
19505 -
polyethylene tape and extruded po lyethylene jacket material has been used for 50 years
present day
1970's present day Cl~ "d 2001
fusion bond epoxy "F BE) was and is being used
- "' . .......,.. •.' -_,... ~ "'""' c..-.-.. "-.,~,.......... ""
"'" =,..... ", ~' Ho...."*''
39
PIPELINES: Coating Examples: ' FB E' & '3 layer' _ FUSION BONDED EPO XY (FBE) : Powder is sprayed onto the hot (220 to 24()OC) pipe
-
-
-
:::;; ....'C!"'!I!II!~"..""
-
_ Coaling is typically 400 to 600 m icrons (0 .4 to O.6mm) thick _ 3 LAYE R: The first layer of the co ating (e.q . 150 microns), app lied above the steel surface of the pipe, is made from FBE Primer. _ The second layer (e.q. 250 micr on s) is a copolymer or spray ap plied im mediately aft er the FBE application . This layer allows the FBE 10 bond wi th .. _ The top layer (e.q. 2.5m m ) consists of either po lyethyl ene (low, medium or high density ) or po lypropylene C _
UO 2001
PIPELINES: ' Fi e l d ' Coatings on Wel ds _ W e will weld our sections of line pipe 'in the field' ~Iy
e c onsecuenuv the ends of each sectio n of line pipe does not contain coal ing (3" to 6"). _ After welding we coat the weld area . _ The 'field' coating we will use depe nds on the main coating on the line , design temperature, etc ..
I I
'MO
' »0
19611
11 7 D
_OhM
1910
1_
200f
-Shook· s.leev es
. rea type of
() . . . . . . . _0:.0-.. . . . . , _ ,"__.,......
....
c_ _. ylpoty.._
'Cut-back' area to be ·field· coaled
C ~ lkl 2001
n"
Wfllp.ll.ape . but we
heat the seeve up and add adhesnre
_G .. _
.',-
e--"",,~~
......
.20
PIPELINES: Internal Coatings _ Some pipelin es have internal coatings a s omenmes we need internal coatings on some lines due to agg ressive product _ Sut on most pipelines we have interna l coatings to improv e flow and intern al coatings are often ca lled 'flow coats
0_ _
_ Coat ings can increas e flow by several percent '
_ Internal coatings can: _ give incr eased pipeline efficiency, due to increased flow rates and reduced co mpresso r/pump costs . • protect aga inst co rrosion during trans port and storage. areouce incidence of 'black dust' in gas lines
a u so of internal coatings is usually based on a cost benefit using flow analyses. etc., but some com panies ap ply internal coatings as 'good practice' 0 _ 1 ... 2001
PIPELINES: Concrete Coating _ Some larger diam eter sub- sea pipelin es are coated in concrete (concrete weight coat ing') to pre vent them floating back to the surfa ce _ This coating (incidentally) also gives protection
Concrete coating
Example of a line pipe
ccanrq below the concrete .
PIPELINES: Are made from welding line pipe
PIPELINES: What Types? •
•
FLOWLINES & GATH ERING LINES - Pipelines serving wells and facilities in the upst ream are referred to as flowlines and gathering systems. These lines trave l sho rt distances withi n an area. They gathe r products and move them to processing facilities , •
Flow1i nes are usua lly sma ll, e.g . 2-410 diameter, and ga thering lines bigger (say 4-12 " )
•
They carry many prod ucts. ofte n mixed tog ether.
FEEDER LINE S - These pipelines move product from processing facilities , storage , etc., to the main transmission lines. •
Typically 6-20io diameter
•
Carry variety of products , somet imes 'belched '.
PIPELINES: WHAT TYPES ARE THEY? •
TRANSMIS SION LINE S - Pipe lines linking the upstream and downstream se ctors are called transm ission sys tems , The se are Ihe main con duits of oil and gas transportation. •
These lin es can be very large diameter (Russia h as 56" diam eter lines)
•
Natural gas transmission lines deliver to
•
indu stry or 'distribut ion' sys tem . erode Oil transm ission lines carry different types of product . sometime
~~~~::=~iR' "'1iiOl!.
r
betched . to refirenes Of storage •
P ROD UCT LINES · Pipelines carrying refined pet roleum products from refineri es to drstnbcncn cen tres
•
D IST RIBUTION LINES - These allow loca l dist ribut ion from the 9<15 transmission sys tem to busi ness , residences. etc.. They can be large diame ter, but most a re < 6"
PIPELINES: Why do we prefer them?
• Pipelin es have been the preferred mode of transportation over com peting modes such as sea, road and rail for several reasons: • they are less dama ging to the environment,
. Iess susceptible to theft, and • more economical, safe, convenient, and reliable than other modes.
"
PIPELINES: World Summary
"00
USA( l 999 - CPS Dala ): Onshore Gas TransmISSIon - 295 .000 mile s
10 00
i' .
~i
'" o •
•• "
Offshore Gas TraO$lllISS'on - 6.000 mile s Onshore Gas Gathering . 21.000 miles Offshore Gas Gathering . 6.000 miles
50. ' 00
Onshore D,sln'bulion · 1.007,000 miles
-
Liquid Transmission lines · 157,000 miles
400 II you laid Canad ian pipeline system, end to end, it would eJctend 17 times
'00
arccro the wodd. There are >3.5milli on km of pipelines
0
UK
C_ue7lfJtl,
Western Europe
USA
Rest of the Worl d
in the world tod ay· .
--_.' -,- ---------'- -" " • _ _ , : - _ » """" ",,,,- ,,-, - " - - ....
PIPELINES ARE GETTING OLD •••• _ 96000 km of pipeline s in the USA in 1942. _ After World War II, big and long pipelines were constructed , due to increasi ng energy demand _ In 2005, >50% of the 700,000 km USA gas pipeline system is >50 years old . The liquid system is older. _ 50 years of proven oil & gas supplies in the world. _ In man y cases oil & gas field infrast ructure is at the end of its des ign life but they still have 25 or even 50 years of production left. _ E.g. -20% of Russia 's oil and gas pipeline infrastructure is nearing the end of its design life . In 15 years time , 50% will be at the end of its design life . _ Many 1,DaDs of km of lines are being replaced , repaired or reha bilitated in the USA every year. _ The US Department of Transportation estimates that 80.000 km of pipel ines will require rehabilitation in the next 10 years . _ Some operators are already replacing their pip elines for the 3rd time . ., " - " - LIO. 2007
50
PIPELINES ARE GLOBAL AND THE WORLD ••• is not what you think•••• IF WE COULD SHRINK THE WORLD INTO 100 PEOPLE. WITH ALL POPULATION RATIOS REMAINING THE SAME .. .. l'EOPlE
P1cOPlE
" " "a "
"""'O<<<'S''''''
"
50 perren! ollhe Wonlh wealth would be on the hands of 6 people - all US ot a ens 80 people woold IiYe m SUb standard holJs,ng ....
70 people WOOJId be unatlle to read 60 people would neverhave used a phone
50 people would be malnouli$hed 1 pef$Oll would Ila..e a college edueahon
...,
A Marna n would dcscnbe lilt: 'normal' earth person as non-white, non-Cbnsnan. poor, malnourished, and illiterate 51
Additional Information
These slides are for information only.
They are based on questions asked by previous attendees, and they are not presented in class.
O_
Lt oL mo.
52
General Information
CI _
53
l.OI 21X)1
'OPEC' . Organization of Petroleum Exporting Countrie
......._.. . ..----_.-.....
_c........ . ..... •
__
1 '-
l 'Oou
• •• _
,-
--
plaItS
2
HYDROCARBONS . Hyd roc arbo ns - natu ral chem ical compounds based on hydrogen and ca rbon are a rema rkab le source of energy.
_ W hen the bonds holding the hydroge n and carbon molecules together are broke n, usually under heal, the energy that went into the bond is released. _ Machines such as generators . boilers and engines harness this released ene rgy to create useful powe r. _ A lthough sma ll amo unts of oil and natural gas seep through the Earth's crust on their own , most deposits are located deep under the surface _ Oil as it comes from the Earth is called " c rud e o il" beca use it contains valuable hydrocarbons - natural chem ical compounds based on hydrogen and carbon tha i contain store d energy - as well as oxyge n and other impurities.
_ A refine ry takes the crude oil and processes it into a variety of hydro carbon categories, either fuels such as gasoline or petrochemicals (i.e. chemica ls der ived from petro leum) used 10prod uce an imp ress ive array of useful products that we rely on every day. 55 Visit""""'.APl.otg fot roore facts
WELLS _ The first we ll in an area is known as an 'exploration' we ll. _ If oil is discovered , further wells, known as 'app raisa l' wells, are d rilled to estab lish the limits of the fie ld. _ If the field is deve loped , some of thes e appraisal wells may be used as 'prod uction we lls' _ The depth of an oil or gas well can range fro m a few hundred to more than 20,000 feet. _ A well is made by drilli ng a hole, ca lled a "we ll bore" , into the earth . _ A rock drill carves a hole into the groun d. As the hole gets deeper, it is enclose d by metal piping ('casing') to keep its sides from collapsing and to keep water and other impurities from entering , e Cement is pum ped through the hole , Whe n the cem ent reaches the bottom of the casing, it is forced out around the end , and pushed to the surface between the outs ide of the cas ing and the well bore, _ This critical layer of cemen t bonds the cas ing to the well bore . It protects oil, gas and underground wate r resources, keeping them from mov ing freely into and out of the well to mix with -- and contaminate -- each othe r _ The diamete r of the hole dec reases with depth, ranging from about 2 fee t at the top to about 8 inches at the bottom . The casing is extended to the bottom of the gas pool The drill is withdrawn, and the casi ng is pierced by an explosive lowered into the shaft .
o p..,,,,,,,, Ud
2001
OIL AND GAS· Where does it come from? _ How does the oil and gas move up thro' a well bore? _Fluids move from high to low pressure areas. The crushing layers of rock around the hydroc arbon put high pressure on it, and 'push' it out thro' the well bore, _The water below the oil and gas may push the hydrocarbon upwards ('water drive'). The gas can act in a similar way if the well bore is into the oil, the gas will expand to fill in the space left by the extracted oil , so maintain ing pressure (' g as drive')
57
EXAMPLE NATURAL GAS SPECIFICATION _ W e control th e content of our natural gas . Example specification": Hydrogen sulfi de
",025 grai ns per 100 fI' 01 gas
Mercaptan s
,; 0.25 grains of mercaptan s per 100 ft' of gas
Tot al su lfur
(i nc. mercaptans and HIS ) S 2 grains per 100 It' of gas
Ox ygen
s; 0. 1"4 by volume
Carbo n dioxide
s 2 % by volume
Nitrogen
s 3 'f. by volume
Hydrogen
no carbon monoxide. halogens. or unsafuraled h)'drocatboos allowed. and no more than 400 ppm of hydfogef'I
Iso penta ne+
s 0 .20 galons of i$0gefl\aOe or heaVIerhydrocarbonsllQOO n' .
L iq uid
free of water and otr'Ief Objectoooilble liquid s g a s must no! contain any h)":lrocarbons which might condense 10liquids
Water
in no event, can • con tain water vapor > 7 pounds per 1 million It'.
O u st/g ums/s o lid s
must be corntnefCialty free of these
H e ating val ue
>9 75 a ro::l< 1175 Btu per
Tempe ratu re
gas to be deliv ered at >40 OF a ro::l<120 OF
O _ U0 200
,
rt3 on a dry
basis
Energy Demand· 2050
, _ _ E""7\' Aqorq<
2 ... _
E_CcvooI. -
- -00;1 ~
59
-- - - --- - - - B ENERGY· Gas Reserves are Increasing *
6,000 Trillion ft3
Trill ion m 3
Other
CIS Am erica Asia Africa
600 500
• Proven
N America
O U lt i m a t e ?
400
Middle East
300 200 100
rsu
U ---:C:-::1
o 1970
2 0 01
Reserves 60
Future Energy Demand· 2050
- us Geological Survey estimates that - at current rate of consumption - the world's entire oil supply will last for 60-70 yea rs
_ Total world consumption of primary energy in 2000': - 10 ,000 Mtoe _ Estimated future world demand in 205 0': a t.ow 14 ,000 Mtoe _ Med 20,000 Mtoe _ High 25,000 Mtoe _Energy demand is likely to doub le I _ _ E_ _
~
_"'''''lI
"
2 W.... E...... CaI. _...__""9
O _ U d 2001
RENEWABLE ENERGY - Market Share'
% 45 Renewables
(ignoring large scale hydro) account for only 2% of the world's primary energy needs
40 35 30 25 20 15 10 5 0
,-
o H yd r o o Sohlr . Wa v e _ T id a l
r-
O W ind
O B io m a •• • Geoth er m
.,-
~
<--
=:LEnergy
----- ......... " " " " -... ....... - . l ,
_
62
)
THE ENERGY FUTURE· Summary
TIME
.....2000 . .
.... 2050
DOMINANT EN ERGY
..... 0
O_UlllO)'
G
63
OIL AND GAS PROJECTS
O_Ull»;'
.
OIL AND GAS PROJECTS - Influence on Project Expenditures and Concepts·
•z
, "on' en
,
U
3
F 'h ~ l_ ng (FEr
~
Final Authorisation & Sa~cllon
~
z
,
Oneconce t
SRECT
PLANNING
Major Influence
,
EXECUTE
DE FINE
,
ABANDON
OPERATE
Rapidly Decreasing Influence
,
,
Low Influence 65 ' Soo
Oft_'.v.,. ''(1('2
PIPELI NES· 'Position in Food Chain' Facilities Eng ineering
Ex ploration and Production
r>.
I r--I ~Oi
Reservoir, Simu lation
G«!
-fi '-
Geophp ics
f"
EX 'kiiliUiiti
il ~
Geoscience
I R"""" o;r I Descr iption
1
~
I
Well Sy
Re",rvoiTntl
1-
-
Controls
Management
rroouction Engineeringg
I
Petro leum Eng meer mg
Pipe lines
I'mce
<:>
1-
Ho't Enginec"t"ing
Pipeline s, etc.
Upst ream operations comprise activities related to the exploration and prod uction 01 crude oil and natural gas Downstream operations refer to the reflnong, market.nq and dis tribution activities for petroleum prod ucts.
66
PIPELINES - Types of 'Line Pipe' and Coatings
67
Pipe Manufacture seamtese pipe
H$
~ _ @;l M. nneSl'l"a nn
£lon\lllKlI
p ll~e.
ERW pipe Forming
~:. o tfC" "
Bead c Ulling
"$-_~,"..f? Splrlllpipe
UO PlJlt
w-
ER welding
- 67-
~
Sut ..."'gM an; wt lding
68
PIPELINES - Longitudinally welded line pipe *- 'S AW' _ A popular we lding process we use is ca lled 'submerg ed arc welding ', so we often refe r to this type of line pipe as SAW line pipe . _ If I pass a high current through and between two metals, I crea te a continuous spark (arc) and heat in the gap, _ If I put meta l into th is arc, it will melt and join (w el d) the meta ls together. A we lder has a me tal rod (electrode) and a workpiece (line " pipe).
_ I can sur round my arc with a granular material or a gas
STEE L PLATE
CR IMP
•
Q
+
'U
If '0 '
('s ubmerge' the arc). This gives me a better weld
WE LDING , FOLLOWED BY INSPEC TION AND TESTING 69
S()JT)() ollho graphics me Illlen from M"fl"esma M . Ge rrno ,' y, liter a ture
PIPELINES - Long itudinally welded Line pipe· 'ERW'* Ano ther weldi ng process we use for longitudinally welded line pipe is 'ERW ' electric resistance welding'
ROLLIl\G PROCESS
HEAT T REAT M ENT
e PO' SI>6'1 Ltd. 2007
WATER TEST
WE I.DING & IJ\SPITTIOJ\
FC\AL Il\SPECTIO~
t
PIPELINES - Spirally welded line pipe'
WELD
PLATE
VISUAL INSPE~
WATER EST
i"'f4...
-~1
'-.1
~,
-~1
X RAY INSPECT
PIPELINES - Seamless line pipe '
CAS T ROU:'\f) Bl LI.ETS ROLLERS GR IP REHEATED
BILLET, AS IT IS PIERCEDA LOl\G FULL LEM jTII
REHE ,\TED & CLEASED PIPE IS SENT TIIRO' A STRETCH REDt:C I\:G \lILI. TO REDlX E TO FThl SHED SIZE
I:-.lSPECT A \" O WATER TE ST
.......',.... .....,''''tL ..,...." ...... ,,,,' .. ~ ,
lAO' ,,..
GAS PIPELINES IN USA· What Are They Made From?
Materials of Construction" Steel ('Line pipe' - API 5L) Plastic Other
% 98.7 1.2 b <0. 1
Prior to 1949, II PI covered GradesA, B,C, but C (yield = 4 0 ,OOO I~ flin' ) W>lS stoppc o in 1930" therefore Gf ade B ;'\oQule produced
,,,,,,,,,",,,, "" w,,,,,,
PIPELINES - Are Coated on the Outside to Prevent Corrosion
.The line pipe is usually coated at the pipe mill. .Older Coatings: . Asphaltic Enamels . PVC/PE Butyl Rubber Tapes _ Coal Tar Enamels
.Newer Coatings: _ Fusion Bonded Epoxy (FBE) _ Extruded Polyethylene (PE) _ Extruded Polypropylene (PP ) . Epoxies/Polyurethanes (EP/PU)
In the mid 1900s , the max im um le mperature o f OUf pi pe lines WaS SOC (122°F) i:l P",, "P"" U,. 2007
Recen tly, it was up to BOC ( 17EY F).
Now. some designs are from 100C to 150C (212-302°Fl ·
PIPELINES - Are Coated on the Outside to Prevent Corrosion _ TEMPERATURE · The tempe rature of the soil, as well as the tempe rature of the pipe may create favourable conditions for attack on pipeline materia ls _ l iquid and gas lines have sligh tly diff erent opet
_ SOIL· Soil struc ture and conditions can affecllhe effectiv eness of the cathodic protectio n, and may also cont ribute 10 the creation of a corrosive envi ronme nt. _ Factors such as so il type, drainage , temperature. CO~concentra tion. and electrical conductiv ity all co ntribute to the env ironment su rrou nding the pipe
OLDER FIELD COATING
_ •• •..-. ". _ r - " " , ~
...
-.-_~....,_
__ ........ ...
__ .. _"*"'-' '
'
PIPELINES - Are Coated on the Outside to Prevent Corrosion (cant.) Thickness, mm • Enh anc ed IiiI Norm al
Hot Temperature L"Imitations. 0 C er
n, CTE
FBE
PEiPP
EPIPU
l imit
'" a
-
f-
,
-
f-
,' I
I
CTE
F8E
PU
PE
Pf'
76
PIPELINES - Concrete Coating on site
e
p""..,., U o. 2001
PIPELINES· A QUICK HISTORY
e P on""", ltd . 200 7
PIPELINES - The Old Days•••• 4QObc BAMBOO PIPE - The Chinese used bamb oo pipe to transmi t natural gas to light their capita l, Peking, as ea rly as 400 Be .
18DOs Wood, iron lead and tin pipes were common in the 1800s to transport water, & in 1821 wood pipe transported natural gas in New York state.
1859
RIVERS/RA IL TRANSPORTATION - From 1859, in Pennsylvania, 0; oil was tran sported In barrels on rive" by horse drawn barnes. '~ This was dangerous - weather & labo ur disputes often disrupted flow. The railwa y relieved this , but the oil was now con trolled by rail _ cbosses and their lOoos of 'teams ters'. .
1861- Sho rt cast iron oil l ines laid with pumps in USA. Team ster s reported t o
63
h ave sa bota ge d o r du g up and de stroyed some of these l ines. 1863 wa s start of 'w ar' between p ipe lines and tea msters .
1864
Proposed long oil line in Penns ylvania opposed beca use it wou ld 'affect loc al prosperity' (probably teamsters opposition).
1865
6" gr avity (no pu mps ) oil line, 700 0 barrelsfd ay, built in Pennsyl vania.
PIPELINES - The first one?
.....
1865 : Partial view of the Benninghcff Run (farm) oilfiel d. The field consisted of 8 7 we lls . most with de rrick s. The righ t. of-way 01Harley's
1865-66 Be nning hoff Run • Sha ffer Farm oil pipeline is seen as a straight wh ite streak on the hill (see arrow). A pumpstation for the line is indi cated . 80
PIPELINES· Recent History •
•
•
1879 : PIPELINE -In 1879 a 108 mile, 6in line was built in Pennsylvania to transport crude, to tank cars for the New York market. • 12 years later the first high pressure, long distance pipeline was bu ilt. They reduced the transport cost of oil from $3 to $1 per barre l. • Initially, all steel pipes had to be threaded together. This was difficult to do for large pipes. and they were apt to leak under high pressure. 1920s: WELDING - In the 19205 stee l pipe and welding became popular in USA • This made it possible to construct leakproof, high-pressure, largediameter pipelines. 19405: LONG DISTANCE PIP ELINES - Long distance pipe lines wer e pioneered in the USA in the 19405 due to the demands of the Secon d World War.
PIPELINES· T h e H istory (1800 ••.) Summaris e d MI LESTO NES INOfVHOPMENl Of PIPElI NE INOUSTRY
"
"_"
,...
UM Uj
Ilio. OO.! '/2 .. H......,
\ ""
us_., eo..0.0, .... '''I, lotI", ... ,.1... fl .. ,
G"'_ _ I"
IOOi. ,......"
\
fin' US ! ~.., ...,.'.' . ,
,...
.n.,••10oo."",,,, I, .. ,;p.t_
1... ~ ..,I. G..: l........ ·T.....
·
.
" " ... .... f " . M ..." .. ';...... ~
/
PIPELINES· The History (1800•••) Summarised MILESTONES IN DEVELOPMENT OF PIPELINE INDUSTRY
F. ,
First gas main laid in london. manufactured in lead
.
First gas work install ed in
First commercial
New World,
use of natural gas
'"
_
Iron pipe Introduced (or
i\ "Baltimore. Md .
natural gas service
'\
"'16
1811
US Supreme Co urt
TransCanade Pipelines completed 2.000·mile gas transmiss ion line \
US Nat ura l Gas Ac t
1843
regula ting gas prices
regulating of well Garprom first gas head gas prices main}n Russia
\
Fil'$' US longdistance pipeline 1110 miles. 6 in.
\
\
-, '8112
First natural gas transportation in the US (2 in. 00. sln miles long)
Tidewater Pipeline)
185.')
First long-distance
all steel gas pipeline (Magnolia G~; Icuistene-Iexes!
18'; (
/ (Alberta.Ontario)IF"';\===f.========f=====";j======9========'R:=;r{ , 19'58 1~ 1938 '925 189~ First high-pressure long distance gas line First majorcross border pipeline Introduction of first x-an pipe lIndiana fields 10 Chicago) US CleanAirAct (Canada-US-Alberta to /
...
California gas pipeline) 1961
her.lding clnn fuel tntroducticn of high - sources IOf pow"
gUide sleellAPI X701 . / to North Ame rica for . / natural gas transmission
bor~~
19100
filSl cross pressure. larger diameter. )-- __ North Sea development high -grade steel marking the offshore (IGAT 1-lran to pipeline industry Azerbaijan pipeline) First Russian gos delivery to Europe (via Poland)
''"\',,,.
tor natural gas uensmisslen in North America (NOVA Gas Transmission)
I
, ...
Composile pipe developme nt for h igh-prO$~ll~e gas
/
2000
I ~ nsml ss lon
...,
\
First use of high-pressure (2.200 psi) X-70 pipe
Figure from - M. Mohil pour, Alan Glover, Bill Trefane nko: Pipeline Repor1: Tech nology advances worldwide gas pipeline developments ', Oil and Ga s Journal. Nov 26, 200 1.
© Penspen Ltd . 2007
k~
tl2
PIPELINES - What are they? I
:
1 1 ·-
. . . . . . . . . ~+ --'--'--
'---+f-""':"~
i
I It. 'I. "-,'"',00
\
_. ' ' ' 0~ . •.Jtt'liit
,
P>p. lm u
Tra ns pon arion
Pr o dU Cl ion
c...".... 5"...,. E,,_ '
L $""
...... SUo,....
Moil_. h"""_
,p"'_ "'...
E. .
c . ...,
s"ofI.n o
--..----_.__......._.------_ __ ..._--......__..__ .--...._ ------..._ .. --_._. -_. __ ._ _
.
.
~
Sor_E
_
PI.....
-
-
.
••_
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PI~ "_ .
OiSlr lbu(l on l
." On5"'-0 _ notr...
'
_
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_
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,
j
-
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-
~._-_.~_._-----
_--~--_._ ,_. _-
O _ l l O 2007
83
PIPELINES - are part of a 'system'
(Receiving fecllities]
Operational support
] -tube s
Wyes
Risers
Tees
[Process equ ipment]
Q gJl\
.~ g
land pipelines:
Hot taps
transmasoa
C-,~~-- Shore approaches Crossings
Flowlines
Cables Manifolds Protection structures
Tr
k lines
Distribution Lines
..
PIPELINES IN CANADA AND THE USA
GAS
OIL
85
PIPELINES - are rela tively cheap • A few years ago, $ 1 would move one ton of petrochemical:
_ _ _ _ _
AIR ROAD RAIL SHIP PIP ELINE
5 MILES 19 MILE S 45 MILES 200 MILES 238 MILES
• In the USA , the cost to transport a barrel of petroleum prod ucts from Houston to the New York harbour is about S1, or about 2.5¢ per ga llon at your local gasoline station (2002 figure s). O _U02Oll '
B6
ENERGY· Oil and Gas pipelines are growing
_Pipelines underway/planned/proposed (km) : -Europe (FSU)
23000
_Middle East (Iran) _Africa (Libya)
13000 8000
-S Pacific (Aus!.) _Far East (India) _S America (Brazil)
•
9000 17000 15000
Largest dev elopments are in the countries in brac kets 87
PIPELINES - Facts on Cost
(>
Poe,,,,," Ltd. 2007
88
PIPELINES ARE COST EF F I C I EN T • In the USA petroleum pipelines depend on a relatively small national workforce of about 16,000 skilled men and women • This work force transports over 600 billion ton-miles of product each year. • These workers accomplish this job so efficiently that Am erica 's oil pipelines transport 17% of all U.S. freight • But cost only 2% of the nation 's freight bill.
89
PIPELINES - are relatively safe •
Road Truck accidents result in deaths at least 87 times more often than pipeline accidents . Additionally, truck accidents result in fires and/or explosions about 35 times more frequently per barrel of oil transported per mile. • These figures include only acciden ts involving petroleum shipments , not all accidents for a given transportation mode
DEATH
FIREI
INJURY
EXPLOSION
TRUCK RAIL BARGE TANK SHIP
87.3 2 .7
34. 7
2.3
8.6
0 .1
02 40
4.0
0 .1
1.2
3. 1
Values I",sslmore than 1.0 indicate nsk of accident is l owe ri g' e a ~e r
th ~ n
pipeline transpon alion,
Compansons based on calculated rates per ton-mile. (Source: Allegro Energy Group) ." Pon ,.,.n Ltd 2007
90
PIPELINE ECONOMICS .Pipelines - can cost typically $1 million/km to build, and compressor stations can cost $30 million . _Therefore, usually one operator supplies a region/industry e 'Ihere must be a detailed economic study prior to any pipeline build _Relative Transportation costs (1997 , Canada): _Oil - Typically, the cost of moving oil amounts 10 aboul10 per cent of the actua l cost of a barrel of oil which in 1997 averaged $27 Canadian dollars. _ Gas · Shipping natural gas costs two to three times the actual cost of the gas itself which in 1997 averaged $1.90 Canadian per thousand cubic feet. _Specific costs - Canadian (1999 - Canadian S) costs for moving oil/gas: .$10.38 to move a cubic metre of light crude oil across Canada
_A cubic metre would fill 1000 one-litre milk cartons _$1.1110 move a gigajoule of natural gas _A gigajoule is enough gas 10 heat a house on a cold winters day 91
PIPELI N ES ARE COS T EF FEC T IV E _ Replacing even a modest-sized pipeline, which might transport 150,000 barrels per day, would require 750 tanke r truck loads per day • That's a load delivered every two minutes around the clock. _ Replacing the same pipeline with a railroad train of tank cars carry ing 2,000 barrels each would require a 75-car train to arrive and be unloaded every day.
j o<
e
h."""", uo. 2001
m".. 'act,
92
ENERGY MEASURES
ENERGY MEASURES _C al ori es are de fi ned as t he amount of heat need ed to raise o ne g ram of water 1° C. _F o od Calo ries act ua ll y refer to kil ocalori es, o r 1,000 calori es _A co mmon ene rgy heat unit is the British Th erm al Unit (Bt u) . e one Btu is t he amo unt of ene rgy required t o ra is e th e heat in o ne po u nd of water by 1° F. 100,000 Btu is ca lle d a Therm a one Bt u is equal to 252 ca lories or 1055 j o ules. _ One ki lowatthour is equal t o 3,412 a t us. 859 ,824 ca lories , or 3,599,660 joule s _The average American adu lt u ses 3,500 k ilo ca lories of ene rgy pe r day, active and resting . Th is is roughly t he t hermal energy needed tor o ne t ub full of hot bath water
,
Btu A MATCH RUNNING A TV FOR 100 hours
GALLON OF GASOLIN E HIROSHI MA ATOMIC BOMB
Calorie
252 7,056,000 28.000 31,500 ,000 125.000 60,000 .000.000 20 ,160,000,000 ,000
DESIGN STANDARDS: 'Overpressures' I \ SMYS oH'"",,,,,,
~
08
i.
. ,... ;
i
tv
.....,. _ II _ 00...-0"" I
Hy
~
A
/\
SAFETY ' MARGIN.....
I
S FETY M RGIN ON AlLuRE
- _. O N SMYS I ,--l-
!I.-'- ~ "'"
I ~::.~~
"
1
:
"
OVERPRESSURES: .
I
, 10 . 15% of MAO. I
PIPELINE ' OV ERPRESS U RE' : Illustration r - - - -
Valve Pump 2
200m
•
Pu mp P2
liq uid Flow. Pump P1 (Max 50 bar outlet )
(inlet -1 0 bou)
' Head' loss due to elev ati on -zebar ' Head' lo ss du e to frictio n, etc. - 20 bar
r-~==;;;;;;;;;;;;;;;r=============~ ' 401
.@:I---~ PRESSURE AT INLET OF P2
.--,
Time (seconds)
'------------ -rr--------" Valve Clo ses: Surge of - to oar .......... • . . ......... .."'......... ..............."""""" . """'...
DES IGN HOOP STRESS: 'Ov e r p re s s u re' Comparison CODE
Hoop Stres s Fact or
ASME 831.4
(using 0.72
ASME 831 .8
0.80
te-l
Maxim u m Inc idental Pres sure
Always check how the cod e allows for Ihese overpressures.
10% 10% (::>0.72)
ASME allows these
4% (>0.72)
as PO 8010 -1
0.72'"
10%
GSA 2662
0.80
10%
AS 2885.1
0.72
10%
{SO CD 13623 0 .77
EN 1594
to 0.83
0.72
pressures to be oyer the design pressure. This me an s that max imum 'surge' or 'incidental'
pressure can
10%
gille1 .1xdesign in liQuid lines.
15%
Th is is high!
-_._ __ -----. . . . ....,_, . . . .. --- ..... -_._-. ,,, ' ,, _ ~
,
_
~ ,, _ ·
.-.~
.n_.. __ .oc
~
~
_-·_
~,.
DESIGN PRESSURE _ The design pressure, p, is the maximum pressure permitted by a code _ It is obtained using the hoop stress equation: _ hoop stress = pD/2t, or P = 2t(hoo p stress )/D, and ensuring this stress does not go above yield. by using design factors (<1»:
_$ SMYS =pD/2t. or p =(2 .SMYS .VD).O _ Other parameters affect our design pressure . _ For example. ASME 831 .8 gives the design pressure. p. as: . p =( 2.SMYS.VD)·O·E.T = nominal wall th ickness. 0 " ou tside diameter. o " design factor = hoop slre sslSMYS t
E = weld pnt or jomt efficiency factor. T " temperature derating factor _ The design tecto- de pend s on joca tco class '. In ASME 631.8 q varies from 0.4 to 0 .8. _ E is to allow for the Quality of the longitudinal or SPiral sea m weld in the pipe. It is based on the historical view on the we ld Quality (strength). In AS ME it varies from 0.6 to 1. _ T accou nts fOf the fact that lin e pipe's strength ero modulu s of elasticity decreases WI th increas ing temperatu re. In ASME it varies from 0 .867 to 1. O ~:IOOII "_'
"
PIPELINE DESIGN STANDARDS : I n t e r n a l pressure c a use s 'A x ia l' Stress
int ern al press ure
.
:
I
..
l~
~
~~
"
PIPELINE DESIGN STANDARDS: Ca lculating ' A x ial' Stress caused by Internal Pressure _ The pressure also causes an 'axial' stress , that tries to elongate the pipeline. e vts canse a long thin balloon being blown up - its diame ter and length expan ds.
hoop
...:;: ) 2:\ )-
_ The ma gnitude of this axia l stress is: _ O.3xhoop stress if expansion of the pipe is restricted , e.q it is buried and restrained by the surro unding soil. . O.511.hOOp stress jf the pipe is capped and free to exp and . e.q at bends.
axial stress, -0.50"0 f~
:+
.. -. .-. . . .-..
-+ -¥-, ..:
......
axial stre ss , V eTo
,~.-.-+
~
~
v is Poisson's rate and is approxim ately equal to 0.3 50
•
PIPELINE DESIGN STANDARDS: ' Ra d ia l' Stress _ W e are assuming that our pipeline has only two stresses: axial and hoop.
Axia l stress
.....~
• Actually. we have three principal stresses in the pipewau. For internal pressure (p) only loading'
.
./ / .../ '.../ R,di,' stress
.///
::~~;~:'t
_ This is reasonable, as pipelines have high Olt ratios, and hence the 'radial' stress is small
. ....
-, ....\
/,/./ .
_ We usually Ignore radial stress, as it is sma ll (=p) com pared to the axial and hoop princ ipal stres ses.
C_
..'
.
Codes g ive gu idance on eo mbl nlng thes e three stresses to give
'equivalent', or ' comb ined' stresses
2006 _'
OTHER STRESSES AND FAILURE LOCATIONS ax ial loa d
b e nd ing mom on!
to" lo"
i "t~rn ~ 1
P"'UUrtl
Poten nar farlure location
I
-'---I'
What if we have a comb ination of these other stresses?
OTHER STRESSES: 'Equivalent' Stresses _ We can have a complex three dimensiona l (tri-ax ial) stress field acting on our pipeline _ But our material properties (e.g. yield strength) and our failu re criteria (e.g. ultimate tensile strength) are all 'uni-axial' parameters
Ax ial 51 .
......i ......
t-"--
,..
55
........•.
Radia l stress
/\
.•••.•.
_ To assess these complex stresses, we group them all into an 'equivalent' stress _T his equ ivalent stress can then be related back to 'uni-axial' stresses and uni-axial failu re
-ln many eng ineering situations stresses exist in mor e than one directio n. ·The direction and magn itude of these stresses influence the onset of yielding. · For exam ple, in tri-axial compression, a material cannot yield because it has "nowhere to go' until there is a breakdown in the atomic structure of the crystals at severat orders of magnitude of stress greater than the uniaxial yie ld stress. 53
/
COMBINI NG STRESSES: 'Equivalent' Stresses _ We have to combine all the stresses in our pipeline, to obtain an 'equivalent' stress to compare it with our yield.
,
.........'
_ We have two theories that help us :
...... ""
.. ......•.
e'Fresca" and 'von Mises'
.....
Radial
I~
Hoop
0equivalent
' T,es ca
<
0 yield
gives ~ igher stress es than von
MISCS
54
COMBINING STRESSES: ' Eq u iv a l e n t' Stresses _ We can calcu late the equivalent stres s:
. Forthree principal stresses (von Mises):
. 0.5[(0"1 - CT2)2 + (0"2 -
0' 3)2
+ (0"3 - 0" ,)2) :s
_ If the third principal stress is negligib le (we call this 'plane stres s'), as is the case in a pipe line for radial stress, we have: _ ° 12 - 0"10"2 +
+
../
)
-.
]---. ,
.
.........
O"axia? -< a yiek:l 2
....
Pipeline des ign sta nda rds require thes e calculations on equivale nt stresses to be calc ulated. The stand ard s then list limits on the se equivalent stress es C_~ I\.'of> 1
LIMITS ON EQUIVALENT STRESSES: Example for Offshore Lines . Pipeline standards limit the level of all stresses in a pipeline , usually by 'des ign factor' . _ We have already covered limits on hoop stress (usually a limit of 72% of SMYS is specified, or a design factor of 0.72)). _ Axial (longitudinal) stresses and 'combined' or 'equivalent' stresses are also limited by using design factors . _ For example, ASME 831.8 and 83 1.4 have limits for hoop, longitudina l, and combined stresses in offshore pipelines and risers: location
De s ign Factor, F,
-,
r7"'-/.~ _ /// r
crl:s cr/
2 . crhoop - O"hoopO"axiar
0/
Des ign Factor, F2
Design Fa ctor,
F,
Hoop stress longitudinal stress Combined stress Pipeli ne
0.72
0.80
0.90
Platform pip ing and risers
0.60 (83 1.4) 0.50 (83 1.8)
0.80
0.90
LIMITS ON EQUIVALENT STRESSES: Example for Onshore Lines . Pipeline standards limit the level of all stresses _ A$ ME 83 1 gives the follow ing limit s for onshore lines: Stress
Limit
Maximum hoop stress
72 or 80% SMYS
Maximum stress due to pipeline expansion, a"
72% SMYS
Maximum bending stress O"b plus axial stress due to pressu re loads, e,
75% SMYS
Maximum (Je plus 0 b plus O"a
100 % SMYS
57
OTHER L I M IT S IN PIPELINE CODES . Pipeline codes will specify other limits. • For exampl e, AS 2885.1: . Product: Appl icable to gas, crude oil, LPG .. .
• Pressure/Stress: MAOP>1050kPa SMYS
or
>20%
MAOP
. Temperature: Tempe rature range is +200C 10 -
T EMP.
30e _ Depth of cover' :
. T1. T2 = 900mm (normal), 600mm (rock
COVER
excavation) _ R1, R2 = 750mm (norma l), 450mm (rock excavation)
ETC .
' MAXIMUM ALLOWABLE OPERATING PRESSURE' _ Always check 'des ign' and 'maximum ' pressure definitions in the relevan t sta ndard and/or regulation.
. Design pressure (DP) is that obtain ed from a
[CODE] (
Y DESIGN
)
national or international desi gn code.
_ Maximum allowable operating pressure (MAOP)* _ MAOP' is in gas pipeline standards and regulations in the USA. _ It is a rating indicating the maxim um pressu re at which a pipeline or segment of a pipel ine may be operate d unde r the nationa l or state regu lations in no rmal conditions.
_ In ASME 831 .8, MAOP is also based on the level of the pre-service lest
IREGULATIONl ( r
)
MAOP
IOPERATOR ] (
Y
M( P
~)
_Th e 'actual' operating pressure or 'maximum' opera ting pressure of a pipeline must not exceed MAO P. ,",Por """" 2006 R,,,,6I'
' w,OP " ,he
""'»"'ed ;n R'V,'.,,,,,,, ., to" USA by to. Of' >eoof p,,,,,,'. s.'
' ""0' "". "', ",.,,0.., p' . "", ' . '. 'IS, _"""9 ,,,, O'}' '" !e(.h"," ' . ,, " Y""
ss
PIPELINE 'DESIGN LIFE' .'Desig n life' . ASME 831.4 says '... a properly mainta ined and protected pipeline system can pro vide liquid transportation service inde finitely' 'Our analysis indicates a pipeline using line pipe of proper design and construction, withstanding a successful hydrostatic pressure test, maintain ing adequate cathodic protection, and protected from outside force damage is capable of performing safely for well over 100 years and possibly indefinitely' USA Office of Pipeline Safely, RSPA, 'Frequently asked questions , www.op s.dct.qov
2001.
60
Introduction to Pipeline Construction
Penspen
Integrity
61
PIPELINES: Constructed in a 'Right of Way'
PIPELINES: Are made up of sections of steel pipe, welded together
_ We buy sections of pipe ('line pipe'), usually 12 metres in length, and weld them toget her to produce a pipeline
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63
PIPELINES: Are made up of sections of steel pipe, welded together
0::
)
PIPELINES: Are made up of sections of steel pipe, welded together
.Pipelines can be onshore or offshore: eonehcre (land) . usually onsho re pipelines are laid in a trench and
wJI1
~:~~hd 10 abo,' 1 melee ( l?'~'k~)O!EC-::-=--J"'·~~) ~
_b urial allows protection, & landscape 10be preserve d Some pipelines are laid above ground; e.g. if the groun d is frozen , or burial is difficult or not requ ired (e.g. a jungle).
I Ir'''':::~~
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PIPELINES: Are made up of sections of s teel pipe, welded together .Pipelines can be onshore or offshore: _Subsea (offshore or under a lake or a ri ver) _ Subsea pipeli nes are laid in a trench on the sea bed, or directly onlo the seabed. _ Larger diam eter subsea pipelines are often coated in concrete {concrete weight coaling') to prevent them float ing back to the surfa ce. This coating inciden tally also gives protection .
PIPELINE CONSTRUCTION: Defects & Damage?
_ Line pipe is tranSJXlrted to. and ohe n stored at, site.
_ Line pipe is weld ed together _ Then put into treoctV seabed and backfilled/ covered .
_ We can have: _ Line pip e defe cts : e,g lamin ation s or sea m weld de fec ts _ Transportation damage: e.q. goug es _ W elding defects: e.q. cracks. a c onstrucno n and backfi lling damage : e.g. dents
PIPELINE CONSTRUCTION: Failures Happen•••
UK _ 1911 _ www.ukopa.co .uk O_2QOOl R""""
68
PIPELINE BENDS
69
PIPELINE BENDS •
Line pipe is flexible and can accommodate ge ntle turns and chang es in elevation
•
But for more severe turns it needs to be bent
70
PIPELINE BENDS: 'Radius' and ' A n g l e' •
A pipeline - particularly onshor e - will need to avoid obstacles. • Therefore it will need 'bends '
•
• A bend has radius and angle (arc) .
•
The bend radius (R) is measured to the centreline of the bend , in multiples of the Nominal Pipe Size (NPS*) - the pipe diameter (0).
--.:;:y ~....-.,..
:.e --~
~
•. _ _
~ Bend Radius , R=1.5D
~
R=1.5D
-""$" d'''''' '' """," 11 """""","."""""' o..n'"I_ NPS " .. . . .o.,,'...,......
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fD 10' ' 2'50". NPS S'.. 00.' H2'l" NPS2' nu O, · ;><·
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PIPELINE BENDS: 'Field' •
"
~
A 'field ' bend is made during pipeline con struction, by taking a piece of standard line pipe and form ing it in a special bendi ng m achine . fl
• Sma ll diameter line pipe (e.q. 6 can be field bent to a minimum of 50 (D=pipe diameter), whe reas large diameter (e.g. 48 ~ ) can on ly be a minimum of 300 )
• The outer portion of a bend has a thinner wall than the inner portion . The cross section of a bend has an oval shape
----T. . ,",
72
PIP ELIN E BENDS: Other types
o
o
• Generally, we use 'forged' bends for tight radius changes, and pulled or field bends for long radius
changes • The forged bends are bought to a specification
~" 9~ Bend Radius , R =1.5D
PIPEL INE BENDS: Other types
o
•
A 'mitre (miter) bend' (also known as mitre elbows), are made by cutt ing and welding the ends of two consec utive pipe joints at an angle
•
They were used many yea rs ago, befo re forged bends were avai lable.
•
They we re made in a shop , for va rious ang les: 5°, 10°, 15°, etc.
•
Many cou ld be combi ned to give any ang le of bend
•
They are not usually used in high press ure pipe lines now , and ma ny codes prohibillheir use in high stressed lines
Mitre Bend •
Multiple mit res are sometimes known as 'lobst er back s' .
o
PIPELINE BENDS: Other types •
oJ..-_D
A 'wrinkle' bend is not usually allowed on pipelines ope rating at >30 % SMYS (see standards for limits on wrinkle bends)
Pressure Testing of Pipelines Penspen Integrity
co ~ 2006 Re>6l1
76
INTRODUCTION: Testing Structures _We test structures before we put them into service, to ensure they are strong eno ugh and/or will perform safely. _We will test a hot air balloon to ensure there are no leak s _We will test ropes to ensure they can carry a specified load _It is the same with pipelines: _We want to show they are strong
enough; and _We want to show they do not leak; _We can do this by filli ng them with water and pressurising the water.
r: I NTRODUCTION: Testing Pressurised Structures
December 1965, UK 150 mm th ick pressure vessel
John Thompson pressure vessel
November 170, UK 28 mm thick p ressure vessel
Robert Jenkins pressure vessel 'np·I/'NwN
' no·;_
'" <, kljJ Li
78
PRESSURE TESTING OF LINE PIPE: At the ' M ill" _ As early as 1869. line pipe ma nufactu rers were 'hydro' testing (testing with water) each sect ion of pipe.
_ By the 19005, the manufacturers were listing the test pressure, that was typically above pipelines' operating pressu res _ Up to the 1950s··/60s · , line pipe manufacturers woul d hydrates! their line pipe to 60% to 90% of the specified minimum yield strength . and cond uct some destructiv e testing 'Mill Test' on individu al length of line pipe (-12m )
@i).~ 60 to 90% SMYS
Water
_ From the 1940$ the manufacturers started to introduce non-destructi ve testing methods to evaluate the seam welds . but it was not unlil1963 that API 5L had mandatory requi rements for the non-destructive inspection
__
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79
PRESSURE TESTING OF LINE PIPE: At the 'Mill'" _ Mili lesting to high levels (i.e . 90% SMY S) was not a requirement in the 1930s: Grade B was required to be tested to between 18,0001bf/in2 to 20 ,OOOlbf/in2 (about 50% SMY S ), according to the rele vant sta ndard (API 5L) .
_ In 1949 API 5LX ('X ' for high streng th) appeared as a tentative standard and established a mill test of 90% SMYS .
_ Hence, it is not certain how mu ch line pipe wa s tested to 905 SMYS before 1949 , but this is of minor consequence to gas pipelines as the vast m ajority of USA gas pipelines were install ed after 1949.
80
PRESSURE TESTING OF PIPELINES: In the Field _ We need 10 know that our new pipeline can contain its pressure, and not leak - So... we can fill our pipeline with liquid (e .g. water) or ga s (e.g. air), raise the pressu re of the fluid (using pumps or compressors)" inside the pipeline to a pressure greater than the normal operating pressu re of the pipeline to determine if the pipeline is leak tight, and can contain a specified pressure' _ This test press ure is held for a number of hours to ensure there are no leaks in the pipeline.
(] CI'-----'-
D .._-"L,~g~U"i,d or gas
~a '
Pipeline (many lengths of line pipe )
C_2OOli1llft6"
._-----_.....___1nI_"' _--_. _.._--...
"
PRESSURE TESTING OF PIPELINES: In the F ie ld . Hence, a pressure lest ca n demonstrate a pipeline's 'fitness for service" , and it ca n be carried out on new pipelines , or to prove the integ rity of existing lines, or to prove the ability of exis ting lines for new ope rating conditions such as increased pressu re, or a new fluid.
8
T
---'OI+ ·-
-"L"';9"u,;,d or gas
Pipeline (many lengths of line pipe )
-----.. . . ..-·0---- -.. _._ --··_ /'OOOl o.-.""" " o
aa
PRESSURE TESTING: Purpose
8J
PRESSURE TESTING: Purpose _ The purpose of pressure testing is 10: _ establish an operating pressure limit for a pipeline; a oetect and eliminate defects in the pipeline ; . check for leaks.
C _ 2 0 0 6 .....6i'
PRESSURE TESTING: Purpose••• Establishing Operating Pressure 'Design Factor' (hoop slressfSMYS)
' Actuatfauu re stress of defectfree pipe is UTS or >1.25.SMYS
1.4 1.2
Safety
Factor'
0.8
based 0 failure
0.6
0.4 0.2
o Des ign os.. . , .. ~
Hydrotest
T ",""". " ••.,. _ , ......
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n ' - " ""- ...., R_
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85
,., "'"
PRESSURE TESTING: Purpose••• Failing Defects • •
A pipeline will ope rate at a 'design' o r 'ma ximum allowab le' pressure The pre-servic e hydrates ! will be conduct ed at a hig her pressur e than this allowab le pressure,
•
~as Design pressu re
Desig n pressur e
Hydrate st pressure
Hydratest pressure 86
PRESSURE TESTING " : Purpose••• What the Standards Say _ 85 1 PO 8010 says the test is to ... prove the strength and leaktightness prior to commissioning, and establish the existe nce of a m argin of safety against failure at operational pressure cond itions. _ A$ /NZ 2885.5 says the test is to ... establ ish the strength and leak tightn ess of a test section , and the pressur e stre ngth of a pipel ine for the purposes of det erm ining or con firming the maxi mum allowable operati ng pressure of the pipeline .
LEAK TEST Water
The hydr ates! is a: -Lea k test, and
·Strength test for the pipeli ne
(
Water
J
STRENGTH TEST e _ _ "",," _
,
-... ..-
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PRESSURE TESTING OF PIPELINES: Types
88
PRESSURE TESTING: Basics••• Types of Test ' _ There a three basic types of pressu re tests : _ A 'st rength tes t' is used to es tab lish the operating pressure lim it of a pipeline segment. _ Typically. the strength le st pressu re ratio (lest pressure/op erating pres su re) is 1.25 and the duration is 4 hou rs or longer. _ Strengt h tests are determ ined 10 be suc ces sful if no pipe rup tures or leaks occu r as per the es tabl ished acceptance cri teria _ A 'lea k tes t' is us ed to det ermine that a pipe line seg ment does not show evidence 01 leak age. _ Typica lly. the lest pre ssure ratio is less than 1.25 and the duratoo is 2 hou rs Of 00g~.
_ Leak tests are determined to be successful if all pressu re venauoosca n be expl ained as per the es tablished acceptance catena. _ A 'spike lest' is us ed to venfy the integrit y of a pipeline con taining 'l ime depend ent' defects (see later). _ The test pressu re ratio is typ ica lly greater than 1.25, and l est durations are typicall y longer than 5 m inutes but short er than 1 hou r. • Sp ike tests are determ ined to be success ful il no pipe rupture s oc cur ac cording 10a pre-determin ed acceptance criterion. 89
PRESSURE TESTING: Pneumatic
r:
0 _
•
'Pneumatic' pressure testing of pipelines refers to the use of air or an inert gas (such as nitrogen) as a test medium instead of water.
•
Pipeline operators rarely use pneumatic pressure testing for systems that operate at pressures abo ve 100 psig due to safety concerns
•
The amou nt of energy stored in a com pressed gas greatly exceeds the energy stored in a compressed liquid. If a failure of the pipeline were to occur during a high-pressure pneumatic pressure test , the sudden release of this large amount of energy could be dange rous to personnel
•
In the USA, its use in large piping systems is limited to lines transporting carbon dioxide under controlled test conditions, or in lines with low stress (less than 20% of yield strength).
•
Many local distribution companies operate their systems at pressures below 100 psig , and routinely perform pneum atic pressure tests on new pipeline installations, pipeline repairs, and installation of service lines to homes and businesses.
2OOlI -.>i ,
00
PRESSURE TESTING: The ' Dy n a mic' Test _ We ca n test our pipeline during servi ce using the pipeline produ ct
Stress e.g. St100/0
_ The American Petroleum Institute (AP I 1110) defines 'dynam ic testing ' as tne application of pressure to a segment of operating pipeline above normal operating pressure under flowing conditions, for a fixed period of time, utilizing a liquid normally ha ndled through the line '. _ Dynamic testing is usually limited to' :
L..-::=====~Time
. 110 percent of the maximum operating pressure of the line , and e a minimum duration of 2 hours,
I
MOP
2':2 hours
L
---.J
API 1110 says that this dynamic test can only be used lor 're-qualificatiorf of a line , and cannot be usedas a bas.sfor increased operating stresslevel. _ ..
... _ _ . _
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PRESSURE TESTING: Basics
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91
PRESSURE TESTING: Basics•.• 'Proving' before the test •
Before a test on a new line, we want to chec k that the line has no blockages or major defo rmation (e.g . dents), and has a uniform diam eter
•
We can check for blockages using a 'gauging' pig. • This is a standard pig , with a soft metal plate (e.g. AI) moun ted on it. • The plate is machined 10be 95 to 97% of th e pipeline's internal diameter
•
If the plate is damaged , there is a blockage
•
If there is dama ge, a call iper pig, or a deformation pig can then be run to size and locate the dam age. As required , 'pig' launche rs and receive rs are wa lded to the end s of the p ipeline sectcn unde rgo ing hyd rosl
PRESSURE TESTING: Basics••• Filling up a p resscrc testing invol ves sealing the pipeline at both ends and providing a water fill location (or other fluids) and several air vents, depending on the length and size of the pipeline .
., PO,..,.., 200& f
PRESSURE TESTING: Basics••• Why is Water the Preferred Fluid? •
We pref er to use water at high pressures, not gas • Natural gas, or air, is not used al very high pressure s • Energy content of a pneuma tic test is ma ny times grea ter than that of a hydraulic test, and can support very long running fractures in the pipeline - should it fail.
Gas
In cold climates a mixture of methanol and water is used
"-"""'-'
95
PRESSURE TESTING: Basics••• Using water" .Typically, the fill water is obtained fro m a surface wat er bod y, such as a river, lake, or g roundwater well. W ater source
Fill and discharge of water
_ We can use pigs 10control the 'flooding' of a pipel ine _ We can put the water into the pipeline within a 'train' of pigs, _ The pigs will sweep oul air, and ensure the pipeline is filled with water, with no air pockets _ The pigs must have good sealing properties _ Several pigs may be used in the train to ensure good sealin g C ~2(II)l;R_' I ~ .".. ,.....
, ..... GTI_I.
96
PRESSURE TESTING: Basics••• Pressure and Hold _ The fluid is pressurised up to the requir ed level, above its ope rating pressure, _ The pressur e is maintained ('held' ) for a required time, to allow for leaks . etc.. to be detected _ The fluid is then rem oved from the pipeline
Pressure or stress - 'Hold' Te st pres sure
or stress
\O~~~;i~ press ure or stress
Time
PRESSURE TESTING: Basics••• Pumping System _ A high volume pumping system (Le. pumps , f ilter ) is used to fill the pipe with
wate r' _ After the pip e is full, the pumping system increases the pre ssure 10 the oestrec level _ The 'l est length' can be as long as practicable (e.g . 15 to 20 miles ), but pipeline confi guration and elevation changes will affect this length _ Elevation increases (e.g . over 6Om) are limited by standards when liquid is used . The fil l pump should be siZed so that the fill pigs will travel at a speed that will mainta in a good seal with the p ipeline. This will reduce th e risk of int rod ucin g air or other compre ssib le mi xtures beh ind the fill p igs. A minim um of 2 to 3 mph is a suggested sta rting point lor the velocity of the fill pigs··.
."
98
PRESSURE TESTING: Basics••• Example of Standard Pressure Requirements •• ASME B31.8 ClASSI FICATION
Test Fluid
Class 1 (Div 1)
Wate r
Class 1 (Div 2)
Water
Class 2 Class 3 Class 4
", G"
Test Pressu re (TP)
Min
M"
1.25xMOP
Nooe
Maximum Allowable Oper ating Press ure'
TP/ l .25
1.1xMOP
Nooe
TP/l .1
1.hMOP
1.1xMOP
TP/l .1
1.1xMOP
1.1xMOP
TP/1 .1
1.25xMOP
None
TP/l .25
1.25 xMOP
1.25xMOP
TP/l .25
Water
l.4xMOP
None
TPJ1.4
Wat er
1.4xMOP
None
TP /l .4
Wat er
",
MaxImum ope ratIng press ure (MOP) is the high est opet almg press ure during norm al opera tion Maxi mum a llowable operating pressure is the max im um pressure allowed by AS ME 631 ,8 Des ign pressure is the max imu m pressure permitted by AS ME 6 31,8 based on ma teria ls and loca tion
• Must be less than design press ure
PRESSURE TESTING ": Basics••• Pressure Hold Period _ The pressure is then held for a preset time, e.q . 8 hours, 10 check the integrity of the pipeline. _ API 1160 states: 'Wi thin limits, the grea ter the ratio of tes t pressure to operatir-j pressure, the more effective the lest'. _ A$ ME B314 currently requires a test pressure of not less than 1.25 l imes maximum operating pressure (MOP), for not Jess than four hours when the pipe is visually inspec ted during the lest. and not less than an additional four hours at 1.1 times MOP when the pipe is not visually inspected during the l es;<. ....
--,.-""-_....
"" ....... '
",-~dT-'~ '
100
PRESSURE TESTING: Basics••• Locating Leaks w hen Using Water*' _ Locating leaks can be a difficult and time -con sum ing pro cess , e v arrous me thods and techniq ues may be used 10 imp rove the opera tor's abi lity 10 find lea ks during a pressu re test including the following :
. Patrol line to locate wet patches. _ Sect ioning or segmenting t he pipeline and moni toring the pressure of each section . Closing main line block valves will isolate the pipe line into sma ller segments . Freeze plugs may also be used 10 isolate sections of the pipe line for evaluation. _ Dyes may be used in the test water 10 improve vis ual indication of the leak
area. _ Acoustical monitoring equipment may be employed to narrow the search
area a o oorants or tracer gases introduced into the test medium during the filling processwill allow the operator to detect leaks with sensing equipment. Testing in short sections both increases the sensitivity to detecting small leaks , and reduces the amou nt of water used • S<>o I;, .,ft AP ' 11 10 , ' 00f
PRESSURE TESTING: Basics••• Following Completion •
Follo wing compl etion of a pressu re test using water, a pig can be used to push the water out of the pipeline ('dewa tering').
Water
• We can use a pig to drive the wate r oul. • In oil lines , a small amount of water in the first productio n is unlikely to be a problem, so a single pig can be used. • In gas and process lines, water can' cause corrosion and hydrates, and these lines may require specia l pigging and drying processes, after 'dewatering' . To' o"
102
PRESSURE TESTING: Basics••• Summary Fill
_ __
I
----- I L-] e -e
To fill 30 miles of a 1l).in. pipeline, you need ~4 0 .000 bbl ctwater. eQuivalent to a 1()(b .1QO.n pond, 22 ft in depth. For 30 miles o f 36-in . pipe, the volume required is X5 as large
'"
Hydrostatic Testing
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104
_ _
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HYDRDTESTING PIPELINES: History••• b efore the
1950s •
The pressure vessel industry has tested its plant by over-pressurising for many years
• the pipeline industry copied this good practice, •
Prior to 1955, construction/operating practices only required a pipeline to withstand SO psi pressure higher than Ihe pipeline's maximum pressure . • Hence, this was a leak test, not a strength test.
•
Testing pipelines prior to operation were not mandatory (specified in regulations) in USA until 1970
>05
HYDROTESTING PIPELINES: History.•. before the
1950s •
Prior to 1955, gas or air was usually used in Ihe test: • Water was used in other industries (e.q. pressure vessels) , but:
• Long pipelines meant water was costly and difficult to use • Dry regions of USA meant that there was no water available • Operators did not want any water remaining in their lines •
As gas was being used, operators did not want to raise the test pressure to levels well above the maximum operating pressure, due to the risk of long fractures .
~~ d
~Gas
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.
CE3
Gas
106
HYDROTESTING PIPELI NES: History••• the birth of hydrotesting •
Testing pipelines to high stresses started in Texas in the 19505 • Texa s Eastern were converting products tines to ga s, and incidents occu rred in-service from manufacturing defects in the pipe .
•
Texas Eastern 's insurers would not support the line s unless the incidents slopped. • Therefore . they hyd rotested the lines to a high stress level (
!'",.."l'"'
High stre ss
""' Water
'"
HYDROTESTING PIPELINES: 'Standard' Test Pressure & Time
•
Historically. pipelines, pressure vessels and piping have been tested from 1.1 10 1.5 tim es the design pres sure .
Pressure :S 1.1
-~- -
Design
• Minimum levelshouldbe1 .1x design pressure (this is design pressure + surge pressure) •
1.25xdesign pressure is ofte n used in standa rds
• The higher the ratio of test pressure to design pressure. the higher the certem ty" that any defect present at the time of the test will not fait at the subseq uent design pressure
•
Time
<"
rocrs
Pr e s sure need s to be 'h el d ' for a time pe riod 10 a llow te m pe rat u re s , e tc . to se ttle.
c Pw.......2006 R_l
"See ASJNZS 2885.5: 2002
'"
HYDROTESTING PIPELINES: 'Standard' Test Pressure & Time
•
Pressure, historically , is held for 24 hours: • to allow leak detection in long pipe lines ; and
Pressure
s 1.1
~~
Design
• due to failures being observed during the hold period .
•
Many pipeline codes do not now require a 24 hour hold period : • for example, ASM E B31.4 requires a minimum of a 4 hour hold per iod at a minimum of 1.25 times the maxim um allowable operatin g pressure
Tim
<2, hours As temperature drops, pipeline pressu re drops.
Leaks are detected by pressu re crop. We must not confuse temperat ure changes with leaks.
Hence, long (8 to 24 hours) hold periods allow the 109 water in the pipe to stabilise with the surrounding soil.
/
HYDROTESTING PIPELINES: 'High Level', and 'Test to Yield' Tests: Stress and Time
•
The concept of a 'high level' test ( ~90'''IoSMYS"), or a 'test to yield ' (100% SMYS ) was introduced into the UK & USA for gas lines in1967 • It was recognised that testing to 80 or 900f0SMYS wou ld not revea l (fail) defects thai ma y cause failure during operation. • These high level tests are popular in gas pipeline codes , e.g . IGEIT D/ 1 requires seam welded pipe to be tested to a desig n factor of 1.05 (i.e. 105%SMYS") .
Stress <':100% SMYS 2: 90% SMYS
Test to yield
",-- _.
High level test
••
·
TIme
Low stresse d (:<>20% SMY8 ) liquid lines (e.q ASME 8 31.4) are tested to 2: design pressure
O P"" ,.,.., 2006 Rev6l, 'BSI POOO1(\-1".' ""
'high '""oj ' . . be ......, 9
1 ~5%
SM YS, ,,"toO. st '...
calo, '",'o,.". ""sed 00
110 """',"', ...11 t h ,"0. "
HYDROTESTING PIPELINES: Offshore Lines •
O ffsho re pipelines are typica lly tested to 1.25 x maximum a llowable operating pressure. or 90% SMYS
•
Many offshore design codes requir e water 10 be used : gas cannot be used in man y codes
•
The hold period is often quoted as 24 hours (e.g. DNV F101 and 85 PO 8010 -2) , but other codes require shorter hold periods (e.g. CSA 2662-99)
as
The British pipeline stand ard PD 8010-2 says a 24 hou r hold period is: 10 ensu re the detection of small leaks in large pipe lines ; and to cover the possibility of creep mechanism causing fail ures after a number of hours .
'"
HYDROTESTING PIPELINES: Offshore Lines •
•
Hydrotesting an offs hore line can be time-consuming: •
Fil ling with water ;
• •
Clean ing and gaug ing' the line : Temperat ure stabili sation; Oissol'ling residual ai r;
•
Pressuri sation \0 the requ ired lest level : HydrostatIc str ength tesl (and leak test ):
•
Emptying the pipel ine (after a successful hyorct est), and disposal of the test water;
•
Drying the pipe line .
Here is an example for a long . offshor e pipeline in the UK M slin g dl uolvl ng equa liz inll t ompe. alU ' o diN " ont ;.1
f ill ing
s:a rt
I
."
Ii.:
L
empty ;nll
- •.
d,ylnll
I I
time -e-e-
-24 hours
j'
approxun a teiy two months 0 __
2OOfi~'
--a..-
_
~
-~
----.,.O;S~
_ .. _
_
-..
• _-
" ' I _ ... . "'
.r- ..
00 . . _ '- . _ _ . . . .....,..,..".
HYDROTESTING: Summa ry of Benefits •
Hyd rotesting o f pipelines is no w acce pted as a means of:
• checking for leaks, • pro ving th e st re ngt h of the pipeline,
)
(
• rem ovin g def ect s of a certain size
( -e-• 'b lu nt ing ' d efe cts th at s urv ive, and this increases subsequent fatigue life, • 'w ar m prest resses' d efect s that surv ive, and this improves their low temperature properties,
(
o
• red ucing residu al stresses
PROBLEMS WITH THE HYDROTEST?: In-Ser vice •
In-service hydroleslin g is a problem due to the pipe line
• being taken oul of service • on average, an in-service bvorotesttakes aboul1 8 days, This is expensive' • acquiring permits to acquire . treat. and dispose of the lesl wate r • the water may be conta minated and requ ire trea tmen t before an enviro nmentally-friendly (and possibly expensive) disposal.
PROBLEMS WITH THE HYDROTEST?: Surviving Defects •
Hydrostatic testing is valuable as a tool to destructively remove 'critical' defects
•
Testing a pipeline above the operating pressu re wilt demonstrate the absence of defects that could result in failure up to the test pressure .
•
But not all defects are removed by the lest, leading to possible 'dam aging ' aspects of hydrolesting, in partic ular: . 'Pressure reversal s' - a defect can grow during the hydrotest, both during the loading and unloa ding . Subsequently, the line can fail at a lower pressure.
_Tim e d ependent grow th - a lest could assisllime dependent cracking (e.q. fatique]. e 'r t ese are net usually a major prob lem unless you have an already defective pipeline.
PROBLEMS WITH THE HYDROTEST?: Surviving
Defects... 'Reversals'· •
A pressure reversal can occur when a previous hydrostatic test cause s a defect to grow nearly to failu re, and when additional defect extension occ urs during pressure unloading. • If this occu rs, then the line can fail at a pressu re lower than the previous hydrostatic test pressure.
Hydratest Press ure Hyorotest 1: Failure
Hydratesl2: Failure
Time
'"
PROBLEMS WITH THE HYDROTEST?: Surviving Defects... 'Reversals' * _6 part wall defects machined into line pipe (36 ", 0.39", X6D) _ All delect lengths = 4.4"
_Defed depths = 0 .078" • 0.195 "
( Jij ••-i!3 euetect NO.1 (d epth 0 .195 ") failed
,-
DofocINo.l ,~_1Iook)
d-x
. Def: cts No~. 2-4, with ~epth ~~' _.i~ 0 .171 .0.142 and 0.125, y.,'>:, J;~ extended due to cracking during ?f~', ·" _ ;;<:;"1: the pressurising rr5 ;~ ~~ ~Jc.'" '
---
seoa
,~,
Do!
DeIO
IU . O.l 71 nl
IU ,Q '~ nl
/......,,,,,,,,,-
-,<'t.2 . ~~ -.. ~.;::$i
a r heretore, defects Nos 2-4 are 10;:,;7··.·_ •-.-,:;.r{i it."" · - ' -,-"':; now deeper, and wou ld fail at a ~~~~~ :>/f;'fr'~ lower stress than defect No 1. ::~, >~~.:':I~ .They would exhibit a "reversal' o,,<..,No.(9 1'l'o:;m
--14."0.125 ")
PROBLEMS WITH THE HYDROTEST?: Avoid ing Reversals· . Pressu re reversals may be a risk in pipelines Hydratesl Pressure containing a large number of defects (e.q. seC) and with mode rate line pipe touqhn ess" Hydrotest 1: . Hydratesting can help. • Wh en we hydratest a pipelines with defects we have two conflicting requirements: . to avoid failures: we want to minimise the exposure of a defect to high stress (as it may grow), abut we also want to maintain the pressure for a period to detect any leaks. • we may also want to satisfy a code requirement for pressu re level . A 'spike' test can satisfy these requirements. " P. , S<>6'1 2006 Re, 6il
Failure
Hydrotest 2: Failure
Time
PROBLEMS WITH THE HYDROTEST?: Avoiding Reversal .. . the Spike Test · WThe 'spike test' has been used for many years in the pipeline business"
~
Stress e.g, 110%
_ It is a sho rt duration (typ ical ly< 1 hour). but high pressure (e.g. >1,25 de sign p ressure ):
WAn initial (high) pre ssure is held for a short time (e.q. one hour)
1-_ ,...':;"
SMYS e.q. 90 % SMYS
SPIKETEST
, \......,,......,
»>
LEAK DETECTION
a This high pressure fails defects . but the short durati on red uces growth
a The pressure is lowe red (at least 5% below the spike-test level) and held for a longer period (as in code . e.g. 8 hours ) _ \0 allow leak detection and code req uirements
Time Most hydrctest failures occur in under a hour
A 'spike' le st is simi lar to a hydrotest, in tha t it wm use water und er no-now condition s, but spike tests are co nducted at the high est
.
.
.
,
,
,
_
'
"
·
~
,
... . . . . . .
"
·.._w .__ ·. . .,.· __ . .
"
possible pressure (frequently 139 percent of MOP), for a very short duration (usually not morethan30minutes) ~
OP......,2OC
. . . . . . . ,· """
'"
PROBLEMS WITH THE HYDROTEST?: Time Dependent Growth * •
A secon d possible damaging asp ect of a hydrotest is time-depende nt defects
•
These can occu r when pipelin e defect growth tak es place due to fatigue , sec, or co rro sion.
•
A lthough this type of crac k growth can oc cur regardless of hydrosta tic test history. it is possible that a hydrostatic te st could initi ate crac k growth that can become sus ceptible to continued time-dependent growth .
•
In this case , to prevent future in-service failures, continued hydrostatic testing wou ld be required to rem ove defects that have ex tended over tim e . • Aspike test, strength test, and/or a leak test can be used to control jnternal and external corrosion • A spike test, or a strength test can be used to control fatigue and s e e ,
O_1'
120
HYDROTESTING PIPELINES: Closing comments . Pre-service hydrotest: always test a pipe to the highest possible stress': _ W ith biaxial stress , a buried pipeline yields at - 1.09 SMYS · , therefore yielding is unlikely at 100% SMYS , but do not les t over 110% SMY$ ·.
• Yielding does not harm pipe ,
. Yielding does not harm coating .
/"
...., ~110%SMYS
' e SA Z662 sta tes thatthe bydrotest should not exceed the lesser of: 8.
110% SMY$ for line pipe, other than continuous welded (continuous welded line pipe {i.e. line pipe that is we lded by heating in a furnace and then pressing the ends of the skerp together, using no filler ) has a hydrates! limit of 66 % SMYS ), and
b.
0 .2% devia tion on the P-V plot.
C _ 2D06_ 1
'"
HYDROTESTING PIPELINES: Closing comments _ Test needs only to be >2 hours (but may be longer for lines with
Pressure
sec,
_ Longer than 8 hours may be of no value (see AS/NZS
2885 .5) _ Extensive load hold and repeated cycling dur ing the test is not beneficial" . particularly at high stresses (see GSA Z662)
Time Time
-SJ~ " " .F
2 to 8 hours???
.... 'I.... _",", . 11
"'I. Ek<>< ~·~T"' ''II
HYDROTESTING PIPELINES: Closing comments _ In-service hydrotestinq is not always the best option: _ Water is difficult to obtain. expensive and polluting . _ Smart pigs can be better, _ Most of the pipe in a pipeline is usually sou nd .... It ma kes sense to use a technique th at will fi nd the critical defects and allow their repair, as opposed to testing the entire pipeline when it is unnecessary.
"'"
Test in-service?
-"
TESTING STRUCTURES: History Location
Method
World wi de
Send fat boy across first
Bridges
UK
Troo p of soldiers
1817
Steam Boilers
UK
Pressure steam testin
before 19 305
Pipelines
USA
Gas testing
19505
Pipelines
USA
1967
Pipelines
USA
196 7
Pipelines
UK
Hydrostatic testin High level testin High level testin
Year
Structure
Be
Ice cov ering
Middle
A as
D_2COI_'
nds
'"
Pipeline Operation
125
PIPELINE OPERATION & CONTROL •
Modern long-distance pipe lines are ope rated mainly automatically by a computer at the headquarters of the pipeline company.
•
The computer mon itors the pressure , flow rates, and othe r parameters at various locations along the pipe , performs many on-line computations, and sends commands to the field to control the operation of the valves and pumps.
•
Manual intervention is frequently needed 10modify the automati c operation , as when different batches of fuels are directed to different temporary storage tanks, or when the system must be shut down or restarted . '26
'SCADA': Supervisory Control And Data Acquisition
• Continuous transmission of pipeline operational data to central control location
• Communication may be wi re, satellit microwave, etc • Allows rapid detectio n of major
CONTROL
incidents without requ iremen for regu lar inspection • Intended for remote con trol.o f valves etc
.
LEAK
SENSOR
VALVE
--------~~ SCADA IN A CONTROL ROOM
'"
Pipeline Pumps and Compressors
©L
ORe"OI'
129
PIPELINE PUMPS AND COMPRESSORS _A pump is a a device that expends energy in order to raise, transport. or comp ress fluids. _ W e use pumps to help transport our liquid s alo ng a pipel ine
_A compressor is a device for increasing the pressure of a gas by mechanically decreasi ng its volume. _ W e use comp resso rs to help transport our ga ses along a pipeline
no
PIPELINE COMPRESSORS
........
Centrifugal compressor
Typica l compressor station
Tu rbine hall
Pipeline Maintenance
1 32
PIPELINE PROTECTION: Corrosion . Pipeline protection starts with a good design and construction . _ e XT ER NA L CO R ROSIO N - We need 10 separate our pipe steel from lhe soil or water environment otherwise it will cooooe (th e iron tum s to Iron oxide). _ Usually. there is no corrosion allowance for elCtemal COO'OSion in pipelines. _ Hence we need to protect our outside surfac e" _ The pipe coaling is the primary orotecnon _ A Cathodic Protection (CP) system is the second ary Int,,",~1 ~ 'ion protect ion <>(;(:urrinyIn wa lt ' ec emonc protection is a techn ique to prevent the pllau corros ion 01 a metal surface by makmq the surf ace the cathod e of an electrochemical cell .
_ INTER NA L CORROSION - We can include a 'corrosion allo wa nce' (inc rease th icknes s of line pipe ) to accom mod ate in-service. predict able. corrosion. But we prefer to prevent intern al corrosion by: _ Treallng the product prior to entry into the line , and checking quality _ Cleaning the line _ MIXing chermcals to Inhibit any corro sion
Eo_ I Conoo.ion occu
EXTERNAL PIPELINE PROTECTION: Coating Breakdown _ Coatings will not be peri ect _ On new pipelines the re will be several damaged areasrkm'
• Pipeline coatings can break down. The major causes are" (Australia): arncc rrect application
."
. a " LICilTOR ~
.. ..o ..
. , a u LTY " I.. T
. , .. CO"'ICT U lc,"ca T'O " _ C" il" OI O ... YI.. O.... I .. T
(68% ) e fncorrect specification (i.e. wrong coating for job) ( 19% ) _ Changes in environ ment since the original specification ( 11%) _ Faulty produc t (2%)
-.-....... """
...
_---
".
EXTERNAL PIPELINE CORROSION: Where? _ EXT ERNAL CORROS ION: _ Old coatings , or poorly applied coatings wi ll allow corr osion _ For onshore lines , externa l corrosion can occu r where the coating is damaged _ For subsea pipelines, extern al corrosion is likely around the 'sp lash zone ' of the riser at the sea surface where wave action is severe .
EXTERNAL PIPELINE CORROSION: Where? • 'Diff erential aeration cells' are probabl y the most common corrosion cell found on pipel ines. • The upper portion of the pipe is expose d to a higher concentration of oxygen than the lower po rtion. • The O2 enr iched environment in the uppe r port ion promotes the formation of a stab le oxid e film . • This is cathodic to the oxygen deficient area on the unde rside of the pipe, which becomes a net anode . G",u od
• Hence, mo st external co rrosion on pipelines occu rs on the lower portion of the pipe
," v ol
Oxyge n ric h
• This a rea must be carefully inspected when carrying out 'direct as sessments' .
Oxygen deficient D6
EXTERNAL PIPELINE CORROSION: Cathodic Protection (CP) _ Corrosion is an electroc hemical reaction that requires the flow of electrons to chemically chan ge th e iron into iron oxide. e c orrosion prevention techniques are designed to prevent or red uce th is harmfu l flow of electrons .
- SO... CP is an electrical way of sto pp ing rust (iron oxide) Pip eline (Cathode)
Sacrificial
Anode
..".
t;'~:i
./""""
.~ .
, . "", ,,~,~ ,, :::
"." . ,po
Elewons fiow t"""" ,d t ~ e ca l~ode in the c >dc rn~ 1 circuit. The cathode is negal ively charged. i.e an ~
~as
a su ffIcient ne ga tive cha rge
ABOVE GROUND INSPECTION: External Corrosion _ C lose Interval Potential Survey - - -_ This survey measu res the pipe to soil pot entia ls at short intervals along the pipe line , to check the CP system . 'CIPS' w ill detect high or low po tentials that may indica te pro blems such as interference from other structures, coating damage, etc .. • Direct Current Vo lta ge G ra d ient
_
.'DCVG' detects coat ing defects in buried _________ pipe lines. _ It exam ines the vo ltag e gradients in the soil from t he CP system, and can locate and estimate a relative size of the coating defect . Elect ro m ag netic Methods . Pearson, ACVG , Pipeline Current Mappi ng (PCM) can locate coating defects >3,
PIPELINE PROTECTION: External Damage
-,g
$-V'"
--------------'~ "Cl . Pipeline protection starts with a good de sign and construction.
_ EXTERNA L DA MA GE - We can protect our lines from third part ies by: _ Thicker Pipe wall, or deeper cover (but beware of overburden). _ Locallng in remote region s,
.¥ . .
_ Regular patrols or surveys of the line, and clear markings, and good comm unica tiOns with third parties including general public, . Protective measur es such as conc rete cas ings,
_ Damage detection equipment.
_._0.. . C_2OOlI_'
",
EXTERNAL INSPECTION AND MAINTENANCE: Onshore
" ~dP-
"#. .
-....
"_2OOlI_.
1ma<:pe5
from
C<>Iumbla Gas. USAaod Tran....,. UK
'"
EXTERNAL INSPECTION AND MAINTENANCE: O nshore Markers . Pipeline ma rkers are used to help surveillance from the air, and also mark its location for mai ntenance and warning
. AS 2855.1 gives these spacings:
Location*
Maximum Spacing (m)
Rural
5000
Semi rural
2000
Suburban
500
High rise
50
'"
INTERNAL INSPECTION AND MAINTENANCE: On /Offshore using 'Pigs'
'"
EXTERNAL INSPECTION AND MAINTENANCE Offshore using 'ROV s'
'"
SURVEILLANCE & INSPECTION: Frequency in UK ACTIVITY
RECOMMENDED MAXIMUM INTERVAL
Aeri al Survey. or 'Vantage' Point Su rvey
2 weeks
Full Wal king Survey
4 years
Leakage Survey
3-9 months "
Landowner/Authority Liaison
6 month (letter), 1 yea r (visit)
Intem al Inspection. or Hydrotest
10 years 5-10 years 20 years
C P Systems
1-3 mcntns ". 10 years (CIPS)
Above Ground Survey (e .g . CIPS ) or
.Depend s on pipeline
'"
SURVEILLANCE & INSPECTION: Purpose DefecUDamage
Method Patrols
Int. corrosion
R R R
Cracks
R"
3 r(! Party Dama ge
P
Smart Pigs
Ext corro sion
Product Quality
Leak Surveys
Geotech Surveys
CP&
Hydrotest
Coating Surveys
R R R
P P
R P
Coat ings
PIR
PIR
Ground movement
Lea kage
R
Sa botage
P
PIR
R
R
P is a proactive, and R is a react ive metho d ~ P.,,,>,," 2006 R...." '.
'"
"Special' pigs need ed
LEAK DETECTION: Need' LEAK RATE in Tons/hour H~le
Product
Pressure
Size (inches)
(Bara)
0.5
1
2
3
Ethylene
25
70
260
620
80
NGL
14
40
140
330
Crude Oil
18
48
180
430
Water
15
40
150
360
15
Gas
5
25
90
200
70
, , !
~
1/
65 25
... "''''''''."W_ •. '_ l..."""'.•""""'" ....., _ s.t... '~ ....,L.. .... ,"00""'''. _50 " ' ''' P_,. - P _ + P_ ~
'"
LEAK DETECTION: Example " _ Offshore pipelines are surveyed for leak s _ For example, in California, the sea surface above all pipeline s that service offshore facilities must be visually inspected weekly for indication of leakage, using aircraft or boats .
LEAK DETECTION: Types .1. Simple Systems ('Seeing or Smelling ') .2. Flow Balance ('What goes in, must come out') _3 . Acoustic or Vibration Sensors .4. System Modelling
Metering
'"
rf
LEAKS: Who discovers them? Onshore Oil Pipelines * Leaks Detected in European Liquid Pipelines Detected by:
No (average spill size, m 3)
%
RoW survey by operator
29 (229)
9
Automatic detection system
25 (188)
8
Third party passer-by
144 (120 )
45
Routine monitoring by operator
64 (388)
20
Hydratest
17 (157)
5
Contracto r worki ng on line
5 (482)
2
Operator maintenance staff
13 (60)
4
Third party worker
20(110)
6
Internal inspection survey
3 (6) l ••",,, " "''' ' ,lOt,,", "'"
... hr
1
·''' ' 'od 149
IC>Po_~,~l,.CO"': AWE,"'.
CONCAW E R.""" no. 1102. Fob 2002 . ........""""'"woH..
LEAKS: Who discovers them? Onshore Gas Pipelines (Western Europe Data) Leaks Detected in European Gas Pipelines
e Pe'""," 2Q06 R. , t!."
Detected by:
%
Public
42
Patrol
21
Contractor
16
District company
5
Company staff
3
On-line inspection
1
Client
1
Landowner
<1
O ther
2
Unknown
8
<~ "
... hr
'U~OPEA~ OM
INC',*N, GROuP (EGIG) (, ... .. G• • Pi""'no '''''''''''''''''h",,<; R_
1"'0-19011), Doc
~"m "".
EG' G " .R OO "
~
,SO
LEAKS: Who discovers them? Onshore Liquid Pipelines (USA)' Leaks Detected in USA Liquid lines %
Detected by: operating Local equipment
pers onne l.
procedures,
personnel
45 27
Third party (excavator. homeowner, etc) operating Remote controllers
If
including 9
Computational Pipeline MonitoringlSCADA 8 with leak detection system Air patrol or ground surveillance
7
Other (induding leak/pressu re test)
5
IL
The leaks continued for many hours. Duration depends on size of leak and detection method. but is typically 10 to 30 hours G _ ~ _'
,,_.""""''''_..._ _ ...... _'~'n' ...~ ..._
~.~
...._._ _...... _ ...... ".",
REMEMBER: Our Pipelines Were Built a Long Time Ago••• So•••? _ Old materers . may be low strength, poo r toughness and con tain defects _ Old joining and cons truc tion practices - may have poo r welds, damage, no QA, etc .. _ Ageing coatings may lead to
corros.on. . Poor records may mean pipe line is not where you think ' . Olffenng products may have been carried leading 10 corrosion . Plpeline may have been mod ified, repaired. erc.. WIthout records . Many dlffenog managem ent l earns may have cared lor the line _ Etc .!
o_~_,
'"
REMEMBER: Our Pipelines Were Built a Long Time Ago ... Deterioration ....
Basic Pipeline Parameters
Penspen Integrity
'I \H iN e Penspen 2006 Re,,;;!1
154
PIPELINES: Review of Basic Terms and Parameters • Pipeline • Transmission and Distribution • Fluids - gases (e.g. methane . ethylene) - liquids (e.g. crude oil. kerosene) • • •
Pipe Diameter Pipe Wall thickness Pipeline material and 'grade' - API 5L - 'Grade' can be 'B'" , 'X60' .
• • • • •
Pipeline design code Product pressure Pipeline pumps and compressors - they boost internal pressure, and help 'drive' the product though the pipeline Design stress/tactor ..; maximum is 0.72 or 0.8 Pipeline protection and deterioration
• •
Leak detection Inspection, maintenance and surveillance ' 55
DESIGN STRESS, 'SMYS', YIELD STRENGTH AND TENSILE STRENGTH •
The te nsile propert ies of line pipe mat eria l are measured as the Yie ld Strength and the Ultimate T ensile St rengt h
•
Th e Pipe Manufacturer ens ures the stre ngth of ou r pipe is above cert ain 's pe c if ied ' minimum lev els.
•
These specified minimu m levels are: • specified minimum yield strengths (SMYS). and • specified minimum ultimate tensi le strengths (SMUTS)
• •
T_
I
T"~ SII""lJlh,
YotOd
S~""lI'h
--- , ,I ,-
.....~.
Ou r actual yield stren gt h and ten sil e st reng t h are above t hos e spec ified Our d es ign st resses (often quoted as a percent of the SMYS) are always well below the SMYS , to give us a sa fe ty mar gin .
C_2OOI_'
I.
~
....-....
"""'""
~
_
_._-
MATERIAL PARAMETERS STRESS . (NlmrnA21
80. 70. 60.
r - -- - Ultimate t
ile strength
t
500 400
i l u re~
300 200
100
•
0
2
•
8
12
STRAIN . %
We 'design' our structures in th region. but they 'fail' in this region, at muchhigher stresses & strains
C_
2OOIl _ '
'"
LINE PIPE: Ductile... brittle.. .. • Materials can be described as 'ductile' or 'brittle' • Ductil e materials can strain (elongate, bend, etc.) extensively before failing • Brittle materials cannot tolerate large strains • Bones are strong , but brittle
C -"",, 2OOIl _
'
'58
LINE PIPE: Toughness •
'Tou g hness' is a me asure of the abil ity of a materi al to withstand the presence of a crack.
•
So , low toughness material (such as glass) cannot tol erate crac ks, and can fa il in a 'brltue ' manner.
•
Very ductile materia ls suc h as alu minium , can with stand large cracks and are high tough ness.
•
Many material specifications req uire a certain to ughness level. In pipe lines, we measure to ughness by a sma ll test called a 'Charpy' test.
•
This is a sma ll impact specimen. •
Theft.toughnes (or lbs.). s is measured in
."
'JOO I:,e:,~'~~~~~
(Chi'~ rr' T"" ,"'_'".... Iro
W _ .. ~""_'."'"D ........ _ ........" ..Sc C<>.oo".,...
O_2OOlIR...rt>1
159
LINE PIPE: Charpy Toughness •
Charpy: • A full size specimen is 1Omm x 10mm:
• If our pipeline steel is too thi n, we use a 'subsize' (%) specimen of 10mm x 6.7mm
[J
•
Typical toughnesses?
6.7
• ol der pipelin es ( 1950 to, say, 1975) will typ icall y have toughnesses (%Cv) below 40J , but • new pipeline steels can have toughnesses abo ve 300 J ''0
LINE PIPE: Effect of temperature on toughness 'uppe r shelf' (DUC TILE , HIGH TOUGH NES)
Toughnes
(Energy Absorbed
'!ower shelf' (BR ITTLE, LOW TOUGHN ESS) Tem perature
161
TOUGHNESS VALUES IN OLDER PIPELINES •
•
The toughness of older line pipe in USA has been estimated as shown here":
15
.=~
80
I
70
I
. m in i mu m
_
average • maximum - - - -
I!;
USA line pipe shou ld be ~ 60 rep resentative of older stee ls in our ;; 5 0 ~I-----business : 0
I
• " I I
• USA sys tem is one of the ~ oldest in the wor ld , and most of'~ 30 the older systems around the :5 20 wor ld used USA specifications 10 and technology. ::
G
•
I
o Toughness of line pipe before B X42 X52 >6 0 X7 0 the mid 1970s is 20-50ft Ib* (f ull grade size specimen), but the newer Grade 'TMCP', cleaner stee ls now can Rememoertnis average toughness level of 2:3Off ..._ _-"",,, 5 (%Charpy, a 20ftlbsJ ... have loughnesses of 300 ft lb.
"' P"""""" 2006.!:IT~\ ·_~.,-,-~ _ _ ,"_,~""...,...,Ro""'_""""'" -" """,,",'~ _
-,__ --.. __
~_
...
"
"
_
~
.•
·_~
c. _ "
,, , . ~ "
'_ · ~
•.
~ ',," ._
".~_
_ ....., .... '"'- '_ 'i'C." """"'_""', , _ """", ~......,.
.... ",..",
162
FATIGUE: In pipelines •
Th e load (stress) in our pipeline can be constant ('stat ic') or it ca n vary ('cy clic')
•
Patlq ue . occurs under cyclic (chang ing) stress of any kind, and can lead to failure. In pipelines this cyc ling is usua lly caused
•
by internal pressure or temperature fluctua tions
Stress
1_
Stalic Stres s
Y\I\J\j'f
Stress
Time
cycnc
S<,,,,
• Not usual ly a prob lem in pipe lines, but • Some gas lines experience large and frequent pressure cycles due to chang ing customer demands
Time
• Oil pipe lines can see some large pressure cyc les e .g. balching • Laying pipe lines offsho re can introduce large cycl ic stresses "' P oe ","" 2000
",,, oil
'63
FATIGUE: From pressure variations •
Pipeline pressure can vary significantly during service • Example from operational liquid line:
.,
'[
0
c. oj
"'":::> '"W
" c,
· 20 '--~~~- ~- -
-w_01-·0
· 10 ·20
·30 .40
·SO
. OJ.()
· TO ·50
---
_
·90 · 100 · 110 . 121l · 130 . \ 40 · ' SO . 160 , ' 70 · ' 80
Days
'"
FATIGUE: Offshore Spans & Risers
.. ,
•• Feed-in
Free-sp an
Feed -i n
'"
FATIGUE: In pipelines
•
Wh y Failures? • The fatigue 'weak ens' the steel and creates cracks thai can grow to fa ilure , or
• the fatigue can cause existi ng defects (e.g. cracks in welds) in the structure to grow to failure. •
1\ Press ure
0, Load
~
Time
Pip elines? The fatigu e can cause existing def ect s (mainly in welds) to grow , & can help stress corrosion crac ks to form /grow, & also cause failures in de nts.
"6
Pressure 0' Load
FATIGUE: A s s e s sment •
•
Time
If we have large and frequent cyclic stresses, we usually use 'S-N' (stress versus number of cycles) curves to ensure we don't fail • Fatigue life is made up of the time for crack initiation, time for crack propagation, and the short time required for final failure. • The presence of a defect or a 'stress concentration' (e.q.a hole), or a weld can reduce fatigue life dramatically. If we have an existing defect, we use fracture mechanics, not 'S-N'
Fatig.e tje a a Hress Rrge ci
STR.CT1RO Ran Rae Rae wth 3 mn darete- t"de Rae v.ith fillet v.elds Rae v.ith 2
100N'rmi' Infiritv
rrmoeeovmch
1
2xl 1
'"
FATIGUE: Scale of p r o bl em •
Extracts from 'W estern European Cross-Country Oil Pipelines an-year Performance Statistics ', CONCAWE, Brussels , February 2002 (www.concawe.be): • Very few ( if any) pipe lines are bel ieved to suffer from deteriora tion due to throughput related effects, for example, meta l fatigu e • Fatigue failures do sometimes occur when pipelines have suffered some construction fault or subsequent damage such as dents. • These are relatively infrequent causes of spillage. • However, fat igue failures do occur, particularly from defects in long. seam welds* : Gas lines: BS P O 8010- 1 states that a fatigue analysis is not required if the maximum cyclic hoop stress is 35N/mm 2 .... ,..,""'.0< R.,,,,,,,,n""_
Wtn
0< Of' "''' " '" 0' '''''''''' " ><'0 '"""0< 10",",",,,,",,, " """"" "'0''''"''''', C"","", 2002, IPC lOO,",''*'
S..m w"'" F.r"", &od<»g _ ' "'
168
(STRESS) SAFETY MARGINS IN A PIPELINE •Actua l failure stress of defectfree pipe is UTS or >1.25 .SMYS
'Des ig n Factor' (hoop stress lSMYS)
1.4 1.2
Safety
Factor""'" based 0
0.8
failure
0.6
0.4
0.2
o Design •... Ol.... ' ' ' _... ,_ ~....--
Hydrotest ~, '_
_
Failu re
~ _''''' '''' ..., "_ ,_ '''''' ''''-OP
W<¥« . '" _ """ " ' '''' '. """" , ","<0,
" _ ARC" , ~ ~.,-
=,
,eo
PIPELINE DESIGN CODES: Special Pipelines·
- us
Army's Inland Petroleum Distribution System (IPDS) . Iraq, 220 miles in length, 6" diameter _ Delivered in 1300 20ft co ntainers _ 1500 soldiers needed to build it . 740psi, 700gallons/min _ 20 pump stat ions on skids _ Line pipe is 19' lengths, aluminium ,
e u euverec in containe rs: 13 containers = 5 miles _ Snap joint coupling damps
' R K,o<"" ",o. R K,""" ",- 'A"", B"Id . R"""'" F",, ' F'• • ·.,0'"'
p,,,.,,,. & G.. """"'ai ,' j'''''' "1 2004 i _
P.O'l""" To &'O""" Ope
''0
Useful Additional Information
These slides are for information only. T hey are based on questions asked by previous attendees, and they are not presented in class.
171
PIPELINE DESIGN: Overview (onshore) _ Select a pipeline route, which is feasible to construct, environmentally acceptable and offers the shortest length at the lowest cost consistent with avoiding potentiall y delay causing government ap prova l or landowner agreement problems; _ Select a design pressure and pipe diameter to convey the req uired maxim um flow economica lly; _ Se lect a n economical combin ation of line pipe gra de and wall thic kness to co mply w ith the chosen cod e;
a u se judgment and experience to select an appropriate corrosion allowa nce and corrosio n protection mea sures ; _ Select appropriate locations for line break valves.
0_2006.....,.'
@m:m!::=~ ~
~¢8fJ ~ij , ~;Ml,tltil
,~ IUl fU
9
!H 172
PIPELINE DESIGN CODES & REGULATIONS· The First Ones.... _ For the USA pipe line industry, the need for a natio nal pressu re piping code became increasingly evident from 1915 to 1925.
_ In March 1926, the American Standards Comm ittee (later changed to the American Standards Associations , and is now ca lled the Amer ican National Standards Instit ute), initialed Proj ect 6 31 at the requ est of the AS ME. _ The industry's object ive was to make a major contri bution to improving public safety by understand ing the ca uses of failures and establis hing gu idance, procedures . and methods for reducing pipeline failu res. _ Bul lhere were no Regulations back in 1926 ..
C_2006_'
PIPELINE DESIGN CODES· Recogn ition This is a review (-2000) of countries who were as ked .. 'would you acce pt the use of these codes?'
%
D A C C E PT o NEGOTIATE • REJECT I--
60 50
40 .c=;
"""
,..
"'"
-
30
-
20
-
10
= -
o ASME
CEN/OTHER
ISO
PIPELINE DESIGN CODES Above Ground Pipelines _ A SM E 8 3 1.4 & B31 .8 are applica ble to both below and above grou nd pipe lines. _ Expansion (temperatu re a nd pressure) can be prevented by anchoring , to ensure ax ial expa nsion and contraction is absorbed by ax ial compress ion or tension , in the same way as buried lines _ If expa nsion can not be ab sorb ed by di rect axial compressio n of the pipe , flexibility has to be provides using loops , bends, offsets, exp an sion joi nts , bellows . etc .. - Above ground pipelines have differi ng all owable longitudinal expa nsion st ress es . _ T he lon gitudinal compressive stress is added to the hoop stress to increase the equ ivalent tens ile stress, and th is is not to exceed 90% SMYS ....... pressure C P...-2OO'l _a. l
--<()
Temperature , pressu re
\ ))--
175
Mechanical Properties
176
STRESSING A PIPELINE
P IPE IS
'0,
P IP E IS
NOT SAFE
SERVICEAB LE
I _N OTE:
STRAIN, %
_ Mosl Grades o JStee l «X80) will deform (strain) a large amount befo re reach ing UTS and failing (e.g. 10%), Howeve r the new high Grade stee ls (>X80j will flo t reach the se high strains , and may only reach 3 to 5% at UTS _ T his is significan t if you are ba sing your p ipeline des ign on strain rather than stress, as your marg in of safety on strain will dec rease with increasing Grade of pipe
«re
m
YIELD STRENGTH OF OLDER STEELS
•
Pipelines are ma de from line pipe steel of various grades The higher strength steels are known by their grad e (X numbe r) and specified m inimum • yiel d st rength (in Ibflin 2x 1000), e.p. x eD is line pipe w ith an SM Y$ of 60 ,000 Iblll'"
• • • •
The lower streng th line pipe are known by the ir grade (grade) and yield st rengt h ca tegory (A,B,C), e.q . Yield strength, Ibffin2 x 1000 Grade B lin e pipe 90 has an SMYS of n·.....'."'''''''''''.'0''''.' R J [ "."e'" 'h lctc"' Con'"" 35,000 Ibf/in' 8 0 s... R..,,,,,,,,".,,,,,,,c .. r""" ""...on P po",e,' J ~ ", ,,,, ' , ,,,,T .c"'>o ,ogy Always check the line pipe 7 0 Coo'. ·. ' CO , e"'\t9". Ma, 'IIlOO" 4J 7 sp ecification - eg API5L
In old pipelines we ofte n do not know the actual yiel d strength There is some data on old North American pipeline steels (see opposite). In ge neral, the lower the stre ngth, the older the stee l
•
@P",,,,,,,,:?'Xl6 R....60"
60 50 40 30 20 10 0
Ell Min
_ Av e O M ax
Grade
30
35
42
52
60
70
H8
TOUGHNESS - How tough is my pipeline? •
An AGA pub lication 'ranked' pipeline tou ghness in terms of age weld etc.: TYPE
GRO UP
AGE
GROUP
WALL & 0 0
GROUP
Seaml ess,
A
Post 1970
A
1<7.6mm , all
A
00
D$AW HF·ERW. IW. Flash We lded
A
LF-ERW, oth er or unknown
B
1960.7 0
T> =7.6mm.
B
A
OD<16"
Pre-1960
t<76mm.
C
B
00>=1 6"'
TYPE
AG E
SIZE
TOU GHN ESS
limit
A
A ,B
A
I
Refer 10 original publication for othe r
A
A ,B
B
II
categories.
A
C
A ,B
II
B
A ,B
A
B
C
A ,B
•
Category I pipe has no toughness
•
$oo V J _ . _ " ' _ _ [ ~ -"II"' ''''-. _ GM _ c-...
1.''''' '9195 ...."""..
'r>o _~"' '''.OO< T l ~·
...
"'
IV
'"
Pipeline Construction
Penspen Integrity
180
PIPELINES - Cost elements CRUDE
5%
,.%
4%
~..........,-----,
,,% ,,%
,,%
37 %
• Pu mp St.llon (2 9 % ) • P ip elin e Con s truc ti on (3 8 % )
• Pump S t a tion (2 7 %) • Plpe ll n _ C o n s truc tio n ( 36 % )
• L ln ep lpe & FItti ngs ( 2 5 %) O La n d & ROW
O LlIn d & ROW
... ,""U$ . ... .--.._-
. Mis c .
C_
• Lln e p lp e & Fitting s ( 2 2 % )
. Mls c .
e-
""'--"" '.... "' T_ ~
>OOI5 _ ·,
-
00 '
'"
PIPELINE CONSTRUCTION - Cost elements .%
LAND
=-- ,
OFFSHORE
• La bo u r ( $ 58 0, 0 0 0)
• M lse.lI . n e ou s ( $ 1 8 0 ,0 0 0 )
• La b o u r . M is c ell an e ou s . M. t e,lal
• Mllt erl al s ( $ 4 5 0, 0 0 0 ) ::::l ROW & Da m a g •• ( S7 0 ,OOOI
. _...--_ ..-.--.-- "
. * '_ ... _ .... _ _ .. ... _ ,__
~
.. "-2OOli ....... '
~_ ...-
_ - ~- -. ~..
- - - _ ..-.. _
"' .
'"
PIPELINE CONSTRUCTION - The Challenge of deepwater
- 90% of the world's offshore structures are in relatively shallow wa ters -
less than 75 metres deep . _ The majority of the world 's heavy deep-water stee l platforms are located in the North Sea on the UK and Norweg ian continental
- -. . "
< ' ,..-
" '~'
-.
' '.
-
shelves.
_ However, the deepest structures are located in US waters in the Gulf of Mexico (441metres) and offshore California (366 metres), compared with the deepest in the North Sea (186 metres). _ W e are going deeper. What does this mean to defective
pipelines?
PIPELINE CONSTRUCTION - The Challenge of deepwater
In 1978, the greatest production depth was 300 m. By 1998 , deepwater production was under way at 1800 m From W'NWworldenergy_o rg
''''
PIPELINE CONSTRUCTION - Deepwater Technology
-
,,~
,
• .li'r=-.
--
IiifI
FPSO RiserslUmb ilinl Anchor
From www.WOI1denergy_org
ta
PIPELINE CONSTRUCTION - The Challenge of deepwater & Decommissioning _ To date some 1,000 structures have be en de commissioned in th e US Gulf of Mex ico: • 70% in waters less than 30 metres dee p and . only 3% in waters deeper than 75 met res. _T he largest steel substructure to be removed so far we ighe d only 6.000 tonnes (the Odi n platform in the Norw egian Continental Shelf). The heaviest st ructures in the North Sea we igh well ov er 200,000 tcnnes _ W hat doe s this mean to pipel ine s?
c p .......... 2OQl; _ a. I
"'6
PIGS AND CLEANING NEW LINES •
Pigs playa key role in new pipeline co n S;lr~u~c::tjo:::n.::s::..
•
A new pipeline will need to be clea ned
•
Th is can be done before the hydratest
_
€~IiIl !~
• If a line has no internal coating, brus h pigs can be used to remove mill scale and rust, and the pig's cups and water flowin g thro ugh the line will remove the debris • Brush pigs may damage internal coa tings
Hydrotesting - Extra Notes
© Pc n5pen 2006
R ~v 6i'
188
HYDROTESTING PIPELINES· Water Not Gas!
..
C ompan'l
There is a huge di fference be tween the energy m a vessel (si mulating a short pipeli ne length) prcssuriscd with air, comp ared to (he sa me vessel pressun scd with water.
...
. i . ..... . . . . . . ' ' ',
•
, Jul..)
,Joo"',
[ n, ' E,> c . . ... . . . ,
I' n. " .... T. " io.
'i'
" .
~
I
1'.\'IOKP,p.
I ~
n.r
Ww&
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r.,.1
..... I~
tJo.I..,
( JOGI. .)
>10 "
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,
l. n . lo,
cro,
4 ... 10.
4 I : I
2~
,,10.
V o iP _ ~ o ) ' 2 M b
' H'" D,,," " ......
. M,.,
...,. ""r"'.'...... .. "".. .,....... .. ,',,-
., . ,."""•• ""· .. ., • v - \·".. .._ -..-._-,,-, _ ,. ..-., ,." " ..".. ., .... ., ,"-',-.. .... , " ,..,. ..' , . . ..." " ..... ,..... .". ....-
. ..._.,,- . ",,-,
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l:
R ati o .. f
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.,If •
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-
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.
. ~
•• .,.
w.r-
.....,;.
I••u l". t '
Pn Ulll al k 10
H ~·d ra u l k ·
450: I
'"
COST' (2002) OF IN·SERVICE HYDROTESTING • Some pipelines are difficult to hydrotest • E.g pipelines that cannot be taken out of service , e.g. those that are not looped • Th e costs are: ft
• Prepa ration for testing: $1.250-S5.000Im ile for a 16_24 pipeline, plus • $2,000/mile to cond uct the test • Loss of throughpu t is the biggest cost compon ent for hydrostatic testing. E.g.: ft
• $7,000/m ile for a 24 gas line. to ft
• $90.000 for a 16 petroleum line "' ft~"" " "
C P......... 2IIOlI _ ! l l
cs
"' .
...._
. " ...
' 90
HYDROTESTING PIPELINES· mechanics •
lmpad of ele vation. Where ee pipe~ne traverses hilly lerra,n, consideration must be given to the selection of seg mel1ts thaI are sectioned for Iesllng - avoid eleva~ons > 3OOfl1ll 8 lest sec1Jon..
•
Where the P'peIine aoSoSeS nvers . roads. railways and Olher access routes, the thoe. wa ll sedlons neee may need to be les led sepa rately. T his may be done before OOI'lstruetJOn or segregated tn:m !tie maio IIoe aod tested III ,solation.
•
If !he test is > '" SMYS. ,I is usual to also reccec ee pl'essu.e-volume If the P-V pIoI relT"Ill"'5lioear, the pipehne should. globally. remaIn elastic. If the plot de'liate$1rom a prewlbed PN rate then ltlI$ IXlUId be a loss of containment or plaS\IC deformatoon in the pope ,
•
Sma _leaks can often be d ,lIieulI to detect; II small change in water/pipe temperature may gIVe the appearance 01 a leak 'ru~
•
Standard
•
The plpeline lesllemperalure may be affected by altrtude .
of lhumtl" use ee temperature measuremeollo COfT'i98"Sllte Iof \his efled. fIWf
CI'06Slf"l9S. exposed versus buned ,
water temperalu'e gradoent etc.
•
•
AIr, eov- lrapped or entrained ..... a lso affect the prnsore-1IOlume reeordotIg
•
If the oecrease in pressure-1IOlume is nol al1nbutable to the eflects eeseeee about IIlT\i1y be neoossary 10 re-~ shol'ter sections of !he popeline to establish and locate a leak
Aftef test ,og. II ISusual to expel the water using compressed a,r tnat wi. I'\OnIIaIly now •
Of
1f1 1he case of liquid lines . !he product
Further dfylrog. mawlly for ga s pipelines. is actlleved ....a \tie use of purpose-buill pog$.. l'oealed air, vacuum. inert gas. or liquid chemical sca venge rs run as slugs .
'"
Pipeline Operation
1 92
PIPELINE OPERATION & MONITORING
ec ontrnuous transmiss ion of pipeline operational data to ceotra l control location ec c mmcnrceuc n may be hard-wirM , or via satellite . microwave etc _Al lows rap id detection of major incidents without require menl lor regula r inspec tion . Intend ed for remote cont rol o f valve s
,
.Throug h the use of Superv isory Contro l and Data Acquis itio n (SCADA) equipment , Product Co ntro l mon itors vo lumes, press ure s and tem peratu res as we ll as the ope rating status of pipe line tacumes. . Using mic rowave , telephone or co mm unicatio n satellites, SCADA p rovides the Prod uct Control ope rator with infor mation on the volu me of p roduct fiowing into the system , the vo lume of p rodu ct deliver ed to custome rs, and the ability to q uickly identify and react to equipme nt ma lfunct ions . The SCADA equipme nt also gives Produc t Cont rol lhe ca pab ility to remo te ly start or stop certain com pressors/p um ps, the reby cha nging ~ow volumes to meet cha nges in cu stome r demand lor natural gas/ oil
>93
PIPELINE OPERATION & MONITORING
194
PIPELINE OPERATING · Costs
For a typical multi-product pipeline in the UK: Land Rates (large corridor of land needed) Electricity (electric pumps) Manpower & Establishment & Legal Maintenance & Communications*
._
32% 30% 30% 8%
~
.F or ,nlo on ", l _
gas pop.. hn.~_ W True.. ~ Repot1 P1peo1on1t~. Fed dal.O show """ 2001 k:>t US gascapaal)' pWone
~~ . ....".
C_2006_,
'"
PIPELINE (European Onshore Crude & Product) OPERATING COSTS' Total Cas h Operating Co sts/annum For Pipeline Only (excluding energy costs)
12
l-
c
g
Total Fixed Cost
~8 ~ ~
84 1·Oll.... rMmi ,
...,
MainteMnc& J
~( ...
ole ...
- . a ll • Coo .. "' Euros
200 400 600 Rep lacem ent Cost, € million
80 0
1000
'"
PIPELINE (European Onshore Crude & Product) OPERATING - Labour Costs' Total Hours worked by both staff and contractors - For Pipeline On ly
300
•• •• ~200
=>
-• •0 0 0 •
•
"-
'i'
~
0
g 100
'" ~
-Other cosl. (lank farms , etc" a re add itiooalJ
200
• Cost in Euros
600
400
800
1000
Replacement Value, € million .,""""",, "_ , , _ ......
""_..."
~
..._ _
...,
o ,,,,~ ~
''''''''''x<~'.''' ' ''''''''''''''. '''' ''= ", ,, -«
PIPELINE (European Onshore Crude & Product) OPERATING COSTS' Ope rating Costs/annum Fo r P ipe line
7%
O nly. includi ng energy 20%
31% • Mainten ance (34%j
. En erg y (3 1%)
-Oth er costs (tank farms, etc " are
o Miscellaneous
• Non.".." inle na nc e staff (20'/.)
ad aitiooal )
II Other Se rvic es (7%)
• Prop erty Taxes , Insurance
- Energy is cos t 01 pump s ' T"~'~ " _ " _
",",=~ ft
0 . . """ ....".
."""""" ''' Y " ' ' ' ' ' ' ' ' ' ""
...,_...... ..
Leak Detection
199
LEAK DETECTION· Types _ 1. Simple Systems ('Seeing or Sme lling') _ The simp le systems involve flying, dr iving or walking alo ng a pipeline and lookin g for evidence of discoloured vegetation arou nd the pipeline, or hearin q or smelling (if the fluid is odo rized) a disch arge. _ Flying along offshore lines may detect leaks in clam weathe r, but wind generated waves will obscure leaking products. _ Some offshore pipeline regulators require regu lar flights/surface vessel visual inspection of the pipeline route every =<30 days . 'Unofficial' pipeline leak detection is performed by members of staff work ing nea r a pipel ine (e.9. on an offshore platform ) or members of the public living nea r, or passing, pipel ines , e.q. farmers (onshore) fisherm en (offshore) . _ 2, Flow Balance ('What goes in, m ust come out') _ Simple line flow balances can be used to detect leakages. _ This involves measu ring inputs and out puts of a pipeline . _ A loss of product is deter mined as the difference between the steady state inventory of the system and the instantaneou s inlet and outl et flows. 200
LEAK DETECTION - Types (cont.) _3. Acousti c Methods ('leaks are noisy ') _ Noise associated with a leak can be detected. _ These frequencies , caused by vibration, can have frequenci es in excess of 20 kHz. Transducers can be clamped to a pipeline, and by noting signa l stre ngth, the source of the leak can be pinpointed. • 4. Pipeline Modelling ('Theory versus Operation ') _ Real time pipeline modelling, which simulates the operation afthe pipeline and continually compares the expe cted with the actual , can offer both detection and location. _ There are commercial packages on the market that may be app ropriate to certain pipeline operations. _ The mod el is a mathem atica l representation of the pipe line and will includ e such featur es as ele vatio n data , valv e and pump locat ions, etc .. _ The model can the n calculate the expected pressu res, flows etc ., and comp are them with what the measu remen ts are showing Any disc repancy may be a leak , and leak alarms can be triggered if this is the case. coP"""",o :1006Rev6l1
LEAK DETECTION ON CURRENT PIPELINES
_ On old (pre1970s) pipelines there are limited leak detection syste ms _ E.g. some form of static leak detection (pressu re decay) and/o r volu me bala nce - based on flow metering . _ If a pipeline system has no SCADA System it cannot have an active or on-lin e leak detection. _P ost 1970s.. . about 50% have some active leak detection system installed . _ The vast majority of new pipe lines will have leak detection by dynam ic modelling. _ New pipeline s in most cou ntries are required to have some form of active/dynamic leak detection system
C Pe",., :1006R" Gi'
202
Pipeline Hatching, Flow & Erosion
203
'HATCHING' . Pipeline companies ship petroleum products of the same quality in seq uence through a pipe line , with each product or "bat c h" dist inct from the preceding or following . • Batching is a method for dea ling with the different pro ducts and product specifications moving through the pipeline _ One refined product or crud e oil grade is injected and begins its jo urney, then another, and another _ Each pipe line establ ishes its own requirements for minimum batch size , based on a number of ope rat ing factors, such as pipe size , flow rat e, ta nkage availa bility, etc .. • Pipe line ope rators must cond uct lesting to ens ure that specification s are maintained ove r th e course of th e movement and quality must be do cumen ted. _ Typical large refi ned petroleum pipe line s tod ay have from 30 - 50 products reg ularly moving on each sys tem ove r a cycle cycle is the pe riod of time from pumping of a certa in grade unt il all other grades are pumped an d the init ial grade is pumped aga in beginn ing the ne w cycle,
_a
_H"" .• "DOC.,~,," , . , ty ' '''' ty,. of ",00' ''' ",mpod '"'00 "D«.... "."'11'" _""'"II" '" """ ' 000 ''"'" 0"" ",00""'0"",,"'" '0"P;D«""... ~"'oe<>j
_ · ""tc~
"" . c """?Oo ",_ "~",,,""ty"'bol h ,_ ", In.""' ''''"",, , ~ _o '''''cn ""''''~ '''"'''','' ~
_,,,,,,,,",,,'.
.... " .. ""m""" .....
;",,"""""" ,""'" ", ,,,",,,, '""' "'" pop,",.,." , ,",,"..-.c. ,hat coo""' ;o tho ,.." jym." ooof ;01oo1"""m ,,.. ; ~
Uni di rectional and b id irec t ion al p igs used in batching
... _ "",",,,~
204
HATCHING· Mixing _M IXING: There is always a certa in amou nt of interm ixing betwee n the first product and the second at the "interiace," the point where they meet. _ If the produ cts are similar (e.g. two grades of gasoline), the resulting mixture is added to the lower va lue produc t. _ If the products are dissimilar, such as diese l and gaso line , the -transmrx," the hybri d prod uct created by intermixing at the interface, must be channelled 10 separate storage and reprocessed .
• SCHEDULING PRODUCT FLOW : .Pipeline opera tors estab lish the batc h schedules well in advance. _O n a trunk line, a shipper must normally "nominate" volumes - ask for spac e on the line - on a monthly sched ule.
..._-
,/'T RAN S M I ~ n l ertace material that will need to be reproces ed)
Compatible Interfaces (no need to reprocess) 205
HATCHING · Exampl e _The Transmountain pipeline in 5ynt h . ,,, Canada transports crude , refined ~ and sem i-ref ined products _Typical products batch train in the mainline is made up of a var iety of materials being transported for differen t shippers and can be up to l=~;;'~ 350 kilometres (217 mi.) long. u""' c"",. _Batches are between 30 and 100 ,..~'t o'" kilome tres (15 and 68 miles) long and range from 8,OOOm3 (50,00 0 bbls) to 30,OOOm3 (180,000 bbls ) respectively. aprooucts move through the pipeline at about 5 kilometres (3 miles ) per hour - equivalent to a walk ing pace
..
206
BATCHING· 'Interfaces" _ PROBLEMS - Problems caused by pumping more than on e pr oduct through a pipe line invo lves mixing of the prod uct s and disposing of the mixed po rtions (interlaces). • PROGRESS - The progress of the different products and the int erfaces must be followed so that the products can be tak en off the line at the rig ht place_ _ VOLUME - The volu me of interfaces depe nds on differences in gravity an d viscosity of adja cent produc ts and on the pressure and velocity of the stream. _ It also depends on the interior co ndition of the pipe. the number of pum p stations, and the distance travel led by the interface. arntertace size can be reduced by maintaining a pumping rate needed 10 keep the heavie st product in the line in turbu lent flow.
_ The size also can be reduced by putling products in the line in proper batching sequence and by keeping the line pressurized during a shutdown . Positive pressure will prevent the speed of the interfaceand the interface volumewill be reduced whether the interface stops on level ground or on a slope, _ DISPOSAL · The differences in gravity and viscosity will also effect interface disposal.
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BATCHING· Delivery Procedures' _ The interface lengthens quickly, as it first starts down stream in the pipeline. _T he farther it travels down the line, the more slowly it lengthens. _ About 65% of the total interface between two products will occur in the first 20% of pipeline distance. _ The dispatcher gives each station the expec ted arrival time of the interface. _ Each station report s the first through the final change of colour or gravi ty, al say - one-mi nute interva ls across the interface. _ Deliveries to storage or to branch pipe lines at intermediate points should be made from 'heart cctsv'. _ The main concern of the station is sening the prope r valves and determining when the interface has passed. _ W hen the sampler open s the delivery valve or branc h line, fuel is taken off at the rate and lime directed by the dispatche r. _ However. the method of disposing of interfaces ma y complicate the switchi ng procedu re at a final statio n .~
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BATCHING· Detecting Changes' _In control of product flow through the pipeline, it must be determ ined where one batch ends and another balch begins There are several methods: _Gravity Differ ence, Batch changes may be detected by differences in gravity of two adjacent products. There may be a great difference, as between MOGAS and JP-8. _ Colou r Change. Batch changes may be detected by differences in colour of two adjacent products. _Dye Pl ug A plug of dye can be injected into a line to separate like products belonging to different customers. Also , it is used to separate similar products with little or no colour differences _Liq uid Buffers. Kerosene or some neutral product (in a small amount ) may be used as a liquid buffer to separate incompatible products. Water is not used . • Physica l Buffers. A physical buffer is an object , such as a pig, rubber ball, or scrape r constructed entirely of polyurethane, placed in the line to separate batches and cut dow n on the interface.
FLUID SPEEDS _Velocities in pipelines vary during the operational stage, pigging operations and construction pigging operations. _Typica l range of cost-effective velocities are as follows: _ Liquid pipelines 1.5 to 2.5 mls _Single phase liquid 1.0 to 4.5 mls _Single phase gas Less than 18 mls (to limit noise) _Two phase gas liquid Greater than 3 mls and less than fluid erosiona l velocity _ For on stream pigging the following are typica l veloc ities: _Liquid line 1.0 to 4.5 mls _Gas line 2.0 to 6.5 mls _Online monitoring pig 2.0 to 4.0 mls _Construction pigging 0.5 to 2.0 mls ' '0
EROSION _ Internal eros ion is usual ly caused by particles In the pipeline fluid Impacting the pipe wa ll. _ Erosion will redu ce pipe wall thickn ess, and it can remove corros ion inhib itor films on th e pipe surf ace, and debris crea ted can block valves . etc.. _ The faste r the fluid flow rate. and the greater the quantity/s ize of part icles, the greater the erosi on _ Areas of a pipeline thai dis turb flow are more susceptible to erosion, e.q. bends or high weld beads. and area s wnere velocity increases . e,g reduc ed bore s. _ There are 3 main mechanism f()( erosion : _ Liq Lid impact by drop$ or Jets . Pa rtide impact _ CavJta lion Of d rople1 collapse
_ impad by droplets ca .. cre ate sha llow craters in duct lle . ne pipe - part>des > 5 11m can ca use 8tO$IOI'l. - cav,la ll(ltl is !he grow'lh a'ld (dIapse of bu bbles due 10 local pressure lIuduallons in a liQuid. The colla pse is aa:ompanied by a rapod flow of liq uid and stress Iluctuallons allhe ~ surface .
cal/$lng efO$lOn. _ For hydrocarbon lines, sand (particl e Impact) from the reservorr is usua lly the main ercsco threat. but other debos (e.g, from corrosion processes) can cause erosion. _ Erosioo usually occurs in high flow rate pipel ines _ Gas lir>es neve t"ghar now rates lh at liquid hnes. and are therefore more susce ptible 10 e rosco _ AbraSloo can occur on lower flow rate p;pelirtes. ,f suffICient parlides a re present. E,g , slurry p,pehnes
_ Erosion can be con trol led by removing the part icle s (e.q . sand screens), controlling flow, ma terial selection (e..g hard coatings on a valve) , etc .. _ API RP 14E give s guid elines on the fluid velocities that will caus e erosion.
'"
Pipeline Security
Penspen Integrity
C L R ew.'l
2 12
SECURITY FOLLOWING SEPTEMBER 112001 General _Terroris m is now a real threat to the oil and gas business. _ W e shou ld neve r be com placent - remembe r thai terrorists attacked the World Trade Centre in 1993 , an d Alge rian Armed Islam ic Group terrorists attempted to fiy a jet into the E iffel Tower in 1994 e rn ere are 3 types of te rrorists 'mmosets' _ RATIO NAL terrorists who perform a ty pe of cost benefit on the ir atta cks to determine maximum impact versus min imum pe rsona l risk . PSYC HO LOGICAL terrori sts who are mot ivated by persona l diss atisfact ion and can not differentiate between right and wrong , do not recognise any views oth er than their own , and will show no mercy or remorse _ CULTURE MOTIVATED te rrorists who are ded icated to a religion, rac e or nationa lity and are aggress ive to any perce ived threat to the ir culture; the ir attacks may inc lude self-annihilation in pursu it of an unques tioning adhe rence to dogma or propaganda _ If you are trave lling abroad , remember that terro rists can be motivated by many things, ranging from rel igion to patrio tic fervour, to environment and concern for animal s. e r nererore. unders tand the cou ntry you are visiting , and obta in the latest security inform ation (e.q. ). _ And remember - as secu rity is increased at officia llgovemmentJobvious locations , the terron st wi ll st rike at 'softer' targets . _ Plus. __ kidna pping is a $1billion/year bus iness , and increasing - don't get caught.. _ Finally, most security prob lems are failures of man agement . therefo re ensu re security is in place TO YOUR SATISFACTION before venturing 10 high risk areas. Your life - your respo nsibility. _
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. ",,"' II 2002
SECURITY FOLLOWING SEPTEMBER 112001 Pipelines... General _M ost pipeline comp anies in USA participate in several alert systems , and coordinate through government bodies to learn of any potent ial terrorist activi ty. _ Companies rehearse, review and refine their security measures on an ongoing basis. Safety and reliability always have been at the heart of everything pipeline companies do. _ A pipeline is monitored all day, every day. A pipeline's flow and pressure are monitored and regulated around the clock . • Companies can deploy extra mea sures. This may involve calling up additional manp ower or sophisticated technology. The tools used to prepare and respond will vary from comp any to company. • Emergency respo nse plans will be in place, as they will be required by local laws/regu lations. _ Ensure your crisis management plans in not just for a shelf - it must be a realistic living document
'"
SECURITY FOLLOWING SEPTEMBER 11 2001 Pipelines.. . Specific _ Actions: . !dentify process for assessing pipel ine system and facility vu lnerabilities - Develop uniform definitions of security conditions - n eveioo graduated set of cou ntermeasures fo r each secu rity condition leve l
. Quick Measures: _ limited access 10pipeline maps/information . Identify key facilities and secure . Background che cks for selected state and pipe line personnel _ Security exercise program . Plan ra pid restora tion of pipeline service following an attack/sabotage ,
_ Some USA pipeline companies are: _ Controlling access, Using intrusion detection , Reviewing electro nic systems aga inst cybe r-terrcrfsm, Preplanning with FBI/m ilitary, Hiring armed gua rd
_ Future: e c ovem ment'tn oustry partne rship to addr ess security needs. A lready started
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Risk Management (insurance)
Penspen Integrity
21 6
RISK MANAGEMENT· Past •
The 1001used by orga nisa tions 10 en su re business and sha reholder valu e is 'risk mana gement':' • 'the process enabling the systematic identification, analysi s and management of critical busines s risk s'
•
Man y ene rgy orga nisations focus on th e 'hazard' risks only • This is achieved by transferring the risk of physica l asset loss or damage to a national or international insurer. Insurers hav e traditionally we lcom ed this type of busi ness. Why?
•
• Oil and gas assets have been good quality over past 20 years • Th ere were m any insu rers in the ma rket looking for busi ness in this type of risk.
•
This has changed .. • Agein g infrastructure is failing • $500,000 ,00001 insured physical losses in Middle East in 2001 and 2002 mainly due
to ageing • Int ernational reinsurance ma rket has red uced from $4 bil lion cap acit y to $1billion to absorb glo ba l energy risk
RISK MANAGEMENT · Future •
•
•
•
Recent ca tastroph ic energy incidents have resu lted in global insured energy claims exceeding globa l prem iums by 100% • Severa l incidents have been att rib uted to ageing infr astructure Insurers wi ll now on ly accept 'high qua lity ' risks • En ergy comp ani es now need to use ind ep end ent risk engi neering reports or asset valuations to man age th is process • How ever, do we need to insure against every risk ? Energy compan ies now need to asse ss all risks, an d provide an opt imum ba lance between risk retention (they carry this ris k and cost) and risk tran sfe r (to the ins urance m arket). Don't 'over-insure'. • Thi s requires an as sessm en t of ALL bu sin ess risks: • BUSINESS · Operational, strategic and financial • HAZARDS· Hazards such as fire, explosions and natural perils We do th is by using con sistent risk processes in a com pa ny • Identify Risks; Analyse/Measu re Risks; De sign Against Risk s; Implement Act ion Plans to Reduc e/Elim inate Risks; Meas ure Success and Improvement s.
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Design Notes
21 9
WHICH DIAMETER AND WALL THICKNESS? _ Most pipe line design codes use OUT SIDE DIAMETER in the hoop stress form ula . _This gives a conse rvative (high) stress. _The more accura te cyl inder hoop stress formula (using both internal and outside diameter) gives value s of hoop stress <5% different from those obt ained using the simple formula lor 011>20. • API pipe has a constant outside diameter (Do). Intern al diameter is Do - 2xwa ll thickness. _ ASME uses nominal (specified) wallthickness in its design stress calculation because: _ when the old versions of ASME 8 31 were written, seamless pipe was wide ly used a r ne under-thickness tolerance for seamless pipe was much gre ater than pipe made from plate. _ The industry did not want to base wali lhickne ss on the large under-tolerance of seamless pipe. _ Using nomi nal wall thickness would cover both seamless and we lded pipe _ It was justified by historica lly safe practi ce a other codes in other countries may use minim um wall th ickness - che ck your codes ! 220
OVERPRESSURES _C hanges in flow, or the sudden closure of a valve, will cause pressure surges . _Pipelines must be protected from these surges (by, for example, a relief valve ). However, because these surges are inevitable, most design codes allow them to exceed the design pressure , providing they are controlled . _Additionally, when setting protective devices on a pipeline , it is impossible to set them at exactly the design pressure. If they were set at design pressure, they would always be activating themselves due to, e.g., minor pressure changes . • Pipeline design standards recogn ise this , and these are accommodated in the allowances for pressure surges. Mos t codes 'allow' 10% overpressures. _ SS 801 0 lim its thes e surges to a max imum of 10% the internal design pressure. IGE TD/1 also limits overpress ures 10 10%, but additionally limits their durat ion to no more than 5 hours at anyone time , or for more than 20 hours per day.
'DANGEROU S FLUI DS" - I n the UK
Acetone Acrylo";lrile ·\ mmon;a ,\ n;!ine Br;ne Bntane
C.,hon \ l ()nox,dc Crudo oilldcadl Crudo 0;1 (l;ve) Eth. "c Frhanol Ethylene Hydrogen Metharle Methano l Oleum Oxygen
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0"
" lamm"h le I;quid hu' no' lo,ic. Boil, . 156.5° Dcfme
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'w )"OS if at"w e 7 bar ye, if alxwe 7 bar ye, if abow 7 bar
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Propylene X' iene
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Toxic g" Flamm. ble I;quid, low varom pre" ", e ("heck vupocr pressure (",h<= al n .4" F1anm' able gas , nol toxic Flammabk ga,. noll"";,, Flammable ga, . nollox;C Flammabk a~ d toxie 1;4U;
to be ad de d 10 th,. li, 1.oon
222
1
PIPELINE VALVES •
Blo ck val ves may be open ed or closed to permit or bloc k the flow of the prod ucts in both directions .
• They are requ ired on both sides of pump stations and major waterways (e.q. 100 feet wide or greater). • They are also selectiv ely placed along the main line 10isolate sectio ns of the pipe inlo sho rter segments. • They may be automatic , remote or manually ope rated. depending on their function. • Block valves may limit loss of prod uct if a spill occu rs. • Block valves include manual gate valves, remote gate valves and station block valves (suc tion valves and discha rge valves). •
Check va lv es allow product flow in one direction and are designed to be held open by flowing oil and to drop closed automatical ly when product flow stops or is reversed. This helps contro llhe flow of the product throug h the pipelin e and limits the amoun t of product which could be lost in the event of a leak.
•
Pres su re reli ef v alv es are designed to open automatica lly when thermal or operating press ure reaches a pre-determined pressure set point. Th is relieves pressure in the line and the valve wi ll close when the pressure is reduced below the va lve set poi nt.
PIPELINE LEGISLATION - Effect of Pipeline Failures · . Majo r accidents can cause pipe line safe ty programs to cha nge d irectio n . , 965. Natchitoches, LA. • The Pipeline Safety Progra m (OPS) was startl:ld as a reactio n to this failure - Gas oocn-o, 17 fatalities . President Johnson staled in 1967 that g,1S pope/me safely was to be assured by new mea sures, . 1986. Moonds View, MN . long Seam weld fail ure . Gasoline failure of W illiams Pipeline ignited . 493 barrel released . 2 fata lities, Env iroom ental damage , . Increase m numoer o f OPS inspectors " ne w leglslallon introduced inr;Judmg lise of IfISlrumen/ed pigs (althou gh the y would not ha ve prevented this failure ) . 1993 Reston, VA. Prior excavation damage . CoIonial Pipeline had a 8)()CJ barre l release of eeser ioto the Potomac Riv er 7,400 barrels recovered by cont alnmeot barrie rs . 1994 EdlSOO, NJ . Mecha nical damage (cracJ( m gouge grew ...mn time ) . Te ~s Eastern gas . ne ignited . Injune5. 2 hours to isola te the rupt ure .....th man ual valve . OPS COtlVened Safely Summit on pipeline research _ 1999 BeN""9ham , WA , Extemal force damage _ Olym pICplpelme . 6 ,600 barre ls of gasoli ne en tered a creek and ignited , 3 fata lities • Generarad major p ublic and congressional sa fely concems. _ 2000 censeec . NM . Internal corrosion foond Inside c.ce. _ 1950 ga s lIne ruptured 12 fata lities - cam pers ne arby, C _2lXl6Rn&1
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PIPELINE DESIGN CODES · Linking i n t o Regulations _ In 1960 , President Kennedy mad e a broad commitment to consumer sa fety.
_ This theme was cam eo forward by President lyndon B. Johnson. _ The Natural Gas Pi peline Safety Act (now called the Pipeline Safety Law 49 U.S.C. Section 60 101 at seq). enacted 00 Aug , 12. 1968. es tablished exclus ive federal authority for safety regulation 01 interstate transmission line s and non-exclusive fede ral authority for safety regu lation of gathering lines in non-rural areas, as well as intrastate transmission and distribution pipelines. _ The mtent of the Law is for sta les to assume responsibllity for int rastat e pipeline safely. wh ile the federal government (U.S. Dep artm ent o f Transportation (DOT). Resea rch and Special Programs Adm inistration, Office 01 Pipeline Safel y (OPS)] retains respo nsibility for interstal e pipeline safe ly . The American Soc iety o f Mech arucar Enginee rs (AS ME ) 831. 8 Gas Trans mission and Distri bution Piping Systems Cod e's 1968 ed ition was used by the Office of Pipeline Safet y (OPS) as a basis for iss uing the Fed era l Pipeline Sa fety Reg ulations as embodied by 49 CF R. Part 192. _ Although the Code may appear to be explicit. its interpreta tion is not as clear-cut. This is part icu larly true wtl ere il is incorporated into 49 CFR, Part 192. The Code do cu ments standards that were developed from years of operating experience and empirical data and is the fruit of ccmretrtec engine91'S reducing complexities into simple practice. _ Th e Hazardo u s Liqui d P ipeline Safety Act (HLPS Al o f 1979. as amended , authorized the DOT 10 regulate pipeline transporteucn o f haz ardous liquid s. _ Bot h of the above Act s have been recoenec in 49 U .S.C . Chapter 60101 et seq .• and give the federal government aut horily ov er pipeline safely for transport Ing hazardous liquids . natural, and other gases. 225
PIPELINE DESIGN CODES· 'Right of Way' _ Writt en agreement s, or 'ease ments', between landowners and pipeline companies allow pipeline companies to cons truct and maintain pipeline rights-of-way (ROW) across privately owned property. _ The ROW varies depending on ._ _... the easement, the pipeline system , etc.. _ The working space needed during initial construction may be temporarily L ....;;;;. ...._ _ .........:.i1 wider _ Most pipelines are buried below ground in a right-of.way. _ The ROW is kept clear to allow the pipeline 10 be safely operated , aerially surveyed and maintained . _ Pipeline companies are responsib le for maintaining their rights-of-way to protect the public and environment 226
LOCATION CLASSIFICATION· USA _ It is of interest to note that a study of fires following a gas pipe line failure showed a cle ar trend between burn rad ius an d pressure, but no correlation wi th pipe diameter (and hence consid ered a second ary effec t). _ The study plotted the ra dius of the bu rn area around a pipeline aga in st pipeline pressure, and co ncluded that an upper bound :
Upper Bound Burn Rad ius for a Gas Pipeline Pressure Radius 260 psi 92ft (28.1m) 987 psi 610ft (186m) _This Table giv es a simple 'rul e of thumb ' for safe di stances (ignoring wind spee ds. terra in, etc.): for example. a pipeline at a pressure of 1000 psi would ca use burn damage up 10 a dis tance of -200m either side of ils corrid or, if il fail ed an d the gas ignited. _ Most gas pipeline failures do not ign ite ; on average, ig ni tion will occur in less than 4% of failures, alt hough failu res in larg er diameter pipelines are more like ly to ign ite (21 % of pipeline mcoents on pipe of di am eter > 16" ignite).
PIPELINE DESIGN CODES LOCATION: AS2885.1 •
Cla ss R1-Broad rur al •
•
Class R2- Se m i-rura l •
•
Loc ati ons in rural areas developed for sm all farms or rura l residential use, where typi cally the area ol tha average allotment is betwee n 1 ha and 5 ha
Class T1-Suburban •
•
Locations in und eveloped ar ea s or broadly far med areas tha t ar e sparsel y popu lated , where typi ca lly the area of the average allotment is > 5 ha
Loca tion s in areas developed for residentia l, commercial or industria l use at which the majority of bui ldings have le ss than four floors , where typica lly the area of the average allotment is less tha n 1 ha
Class T2- High ris e Locations in areas deve loped for residentia l, commercial or ind us tria l • use at which the ma jority of bu ildings have four or more floors, where typically the area of the average allotmen t is le ss than 1 na
I ~""llo'. = to ,OOOrn'. 2 47 acres
228
PIPELINE DESIGN CODES - WHY HAVE A LOCATION CLASSIFICATION? _ SAFE TY : The intent of a pipe line design cod e is SAFETY . A loca tion classification scheme helps us design a safe pipeline . but how? .PREVENT THE UNE BEING DAMAGED : We know that the major cause of failures in onshore gas lines is damage to the tine (eq .) by contractors digging foundations lor bui ldings. or farmers digg ing drainage ditches. a t heee activities are necessary, inevitable , regular. a'rnererore. we can achieve safel y in a gas line in two ways: a 1. We can ensure that there are few ac tivi ties around ou r pipeline that will damage the pipeline, and cause it to fai l (proactive . decreas e prob ab ility of failure) e z . W e can ens ure that if our pip eline fails there are few pe ople around the pipe lin e, and hen ce reduc e cau salities (reac tive ,.. decrease consequences of failu re), _ It is always better to be pro active , therefore the intent of the ASME 8 31.8 location classifications is to reduce the number of buildings arou nd a highly stressed pipe line , and he nce reduce ali lhe associated activities that can damage my line, _ The log ic is .. . the more buildings .. the more activities ... the more limes my pipe line will be damaged _LIMITED CONSEQUENCES : An add itiona l eff ect of having less building s around the high stres sed pipe line is that - shou ld it fail - it will have limited consequence s. 229
Software & Management
230
REMEMBER••• Software & Computers....
III = ~ ~
""
see ~ ses =
_ We are using compute rs and software to design and o~~ our pipeline _ The Ameri can Soci ety of Civil Engineers reviewed" failures in 52 struct ures attributable to comp uter errors : Effect of Error
Cau se
%
%
' Poor solut ions ' to problems in eng ine er ing
63 %
Computer Hardware
13%
Poor performance
6%
Software
Catast rophic failures
4%
Us ers
25% 58'%
Unk nown effect
27%
Ot he rs
4%
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REMEMBER ••• Software & Computers•••• (c o n t .) a t.essonsv: . computer hardware and software (operating system, general , and civil engineering) are not infallible, _ diagnostic software used to check flaws is not infallible, _ no amo unt of testing by the vendor or user will assur e thai ha rdware and software will be flawless, but testmq does help reduce the number of flaws . _ newer versions of software . beca use of bugs. do not always perform as well as older and tested versions. and _ the owner. engineer-of-record. superv isor, etc. should not accept comp uter-aided analys is and design done by any user. unless the results have been shown to be verified by independent meth ods .
.1-
'"
REMEMBER... Finally•••• -Do not assume that you have a perfect pipeline, if it is des igned to 'code ': _CALCULATIONS ARE NOT ENGINEERING experience . etc .
you must add jUdgement,
• CODES DON'T INCLUDE EVERYTHING - It is a fact thai many pipeline codes do not require leak detection systems, do nol requ ire automatic shut off va lves , do nol requi re interna l inspections . '~ _CODES INCLUDE SOME GOOD THINGS, BUT YOU DON 'T HAVE TO USE
THEM - in USA, pipelines must be designed 10carry smart pigs, but operators are not required to run smart pigs _ _ MANAGEMENT IS KEY...You can have an acceptable pipel ine design .. you can have the most modern materia l.. . but you MUST have smart managers both designing and funning the pipeline' _SMART PIPELINES , SMART ANYTHING, ARE USELESS WITHOUT SMART MANAGERS 233
Corrosion Notes
234
EXTERNAL PIPELINE CORROSION· Cathodic Protection (CP) a u njess corrosion is controlled or mitigated , all steels. if buried in soillwater, w ill corrode : e corrosion is an electrochemical proces s: 8 a currentleaves a structure atthe anode site , e passes through an electro lyte . 8 and re-enters the structure at the cathode site 8Therefore if a metal object's surface can be turned into a cathode over its entire surface , then corrosion can be prevented on the metallic struc ture.
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235
EXTERNAL PIPELINE CORROSION · Cathodic Protection (cont.) _ CP can use either a 'sacrific ial' anode ' or 'impressed' cu rrent.
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236
EXTERNAL PIPELINE CORROSION - Cathodic Protect ion - Summary a c orroslon is a DC phenomenon related to the energy stored in the metal. _ A steer is in contact with an electrolyte, soil or water, releases energy back into the earth and attempts 10 return to iron oxide . e r o keep energy (metal) from returning 10 the soil, another energy form mus t be applied on to those buried surfaces thai is equ al to/greater than the energy tryi ng to be released. _ This is the CP system's function , subs titu ting a sacrific ial metal 10 corrode in place of the pipeline or stru cture . • Thi s maintains the ene rgy level of the structure _ To ensu re t he CP protects a steel structu re it is necessary 10 have the steel at ce rtain negative poten tial with regard to the environ men t in whi ch il is buried/im mersed . • For steel it is - 0 .850 V measured against a Cu fCu sulphate-type electrode .
EXTERNAL PIPELINE CORROSION Protected/Overprotected Potentials •
•
•
As CP protec tion current is app lied, the pip e potent ial becomes more negative and the corros ion rate slows . -0.6 When sufficient curr ent is app lied and the specified criterion is reached, -0.7 corrosion stops. Excessive current is wa stefu l of energy ·0.8 an d causes overprotection . •
•
Overprotecnon can cause disbond ment of coatings & embrittlementof stee ls
The original National Association of Corrosion Engineers specification for bur ied uti lity pipe lines proposed the following criteria for detennining when a steel or cast iron structure is cathodically protected (NACE
RP0 169): • A voltage of -0.85 v rel"lliv8to a copper/ saturated copper sulphate
No Protection - Active Corr O'
501119 Prot.dion
-0.9
.1.0
Some OverprotllCUOIl
·1.1
~Qte<:tIon
·1.2
poten!'''~I:-----------'' Cu /CuSO.
electrode 238
INTERNAL PIPELINE CORROSION· Where? _ INT ERNAL CORROSION : _ LOCATION ALONG LINE - Interna l corrosion is like ly in low spots in the pipeline, and uphill sections, or at riser elbows , where brine , bacteria and
other corrosiveagents can collect. . POSITION AROUND PIPE - tnterna t corros ion tenos tc occur in the botto m of the pipeline (around '6 o'clock) , especially in gas lines, as the corrosive substances tend 10be heavier than oil or gas . 'Top of the line' corr osion t- 12 o'c lock) can occ ur under condensing cond itions . PREFERENTIAl CORROSION· Prefer ential corrosion of welds and heat affected zones may also occ ur (see Wel d Defects lecture ).
INTERNAL PIPELINE CORROSION - Inhibitors .How can we control internal corrosio n? One way is .. . inhibitors. _ Corrosion inhibitors are substances which, when added to a particular environment, decrease the rate of attack of that environment on a mater ial such as steel. a c crrostcn inhibitors can extend the life of pipelines, prevent system shutdowns and failures, and avoid product contamination .
_They reduce and inhib it the contact of metals with their corrosive environment _ W e can place them in oil and gas: - Several kinds of inhibitors can be used to inhibit the corros ion of natural gas pipelines and oil lines
O_2006~1
'"
Other Information
241
PRESSURE TO STRESS • •
Usuall y, the main load on our pipeline is from the pressure exerted on the pipe by the flu id in it. Pressure is a force that will expand o ur pipeline. Pressure . When express ed with refere nce 10 pipe, it is the force per unit area exerted by the mediu m in the pipe • Atmospheric pressure (P a tmos ) - The pressure due to the weight of the
atmosphere (air and water vapour) on the earth's surface. The average atmospheric pressure at sea level (for scient ific purpose s) has been defined at 14.696 pounds per square inch absolute , • Pressure abso lute (Pa) - (usually ' PS1A' ) - Press ure in excess of a perfect vacuum. Abso lute pressure is obtained by algebraically add ing gauge pressure to atmo sphere pressur e. Pressur es reported in "Atmospheres" are unders tood to be absolute. Absolute pressure must be used in equat ions of state and in all gas-law calculations. Gauge pressures below atmospheric pressur e are called "vacu um." • Pressure gauge (Pg) • (usually ' PSIG' ) • Pounds per square inch above Pg + Patmos W e use gauge pressure in the atmospheric pressure , P, pipeline industry
=
Logon to
for mo re definitions
'"
CONVERSION UNITS 1 inch ::: 25.4 mm 1 mile e 1.6094 km 1 mile per hour ::: 1.6094 km per hour '" 0.447 metres per second 1 pound (Ib) = 0.4563 kg 1 Newton" O.225 1bs
1 bar e 14.5039 psi Weight: 1 cu in of carbon steel" 0.283 lbs > 0.128 kg 1 cu m = 7810 kb = 17300 lbs Flow: M/sec :::(barrel lday)l275 [)2
o ::: inside diameter of pipe in inches
FI/see" (barreUday/63.82[)l
C_2ODII"*"f."
CONVERSION UNITS To genmat,., lG Wh (1.000 .000 ,OOO· wattsl hou r) of e lectllc ity fro m a 30% effic ient pow er station , you would need:
500
metnc tc nnes 01coal, or
280
me tric tonnes 01o il (2100 bar rels oil) o r
115.000
th"lr ms of natural gas (316,250 eeoc me tres. 11.5 m illion cu bic f,,!!t) .
MASS
"g
· 2 2Q46 1b
1 me tric tonne lion (UK) l ion (US A)
= 1000 kg = 224 0 Ib f Long" ton )
= 1,102 3 ton ( USA)
z 2000 Ib ('Shorf Ion )
=901,18 1<.'1
VOLU ME
, m'
• 3531 It'
l li1re (I) 1 gallon (U K)
= 0 264 ga llons (gall USA
1 gal (U SA ) 1 BSL
· 3.1851 = 42 gal
= 0 90 718 metric
""M
• 1 20095 gaIons (U SA)
= 159 1
HEAT AND ENERGY
'8_
,
""~ 1 GW h I kcal
· 1.055 kJ . 100.000 Btu ·34.121Iherms = 4186 8 J
· 0 252 kcal = 105.506 KJ
= 0.00)295 kWh
=0.001163 kW h
= 3968 Blu
=293kWh
'"
CONVERSION UN ITS Cro d e oil :
1 barrel ( bbl)
~ltes
lb_
I 0.15898729 cubic metres
1 banal per day
t 48.8 tormes per year"
1 bafTeI per day
1 58 .03036 cubic metres per year (365
1 starodard ec ec metre (scm,
! 628981 barrels
1 standard cubic metre
I 0.84 eones of oil equivalent (too)'
1 tonne
! 749 barrels'
Nat ural 1 cubic metre
gas
158 .96 729
1 wbic 1001
! 3531461 cubic feet 1 1ooo 6 1u (Brit ish thermal unit)'"
AOJboc metre (see also
Sm ' ) " 629 barrelS z 0
Nm' . 35.3 $Cf. 37.3 Normal ecee metres (al JICITl) at a reference of O'C and 1 01325 bar , a lso 5m 3 Sm J : Stand ard cubic me tre (a lso scm) ill a reference co ndition of lS"C and ' .01325 bar See also N m
OM standard cubic foot I~O
,"
per day (sd d) · 10 stand
cubic me tres per year. GSm' (gscm) GIQ3 sian da rd 1 cone fool j 0028317 eeoc metres cu bic metres = ooe bil l~ 1000 cubic metres 1 cubic meier r:A oil equivalent'" cobie metres o f g as at 0-01325 bar and lS "C. • ~ 18(;\(11"1, 10< OiI-.......lenl are ClIk:u"'lo>d from \lie _ _ C8lonfioc ~_lor each poIIOIeI.on type ., ~ on II>e0f'0S*<:aIonlic value (GCV) 01!he gll$ ••• Oec>ends on IN COl allloB ~ an:l lhe reIeI""Oll ~d !fie 001 C_
2006 Rao.io.'
,<5
Pipelines: Their Safety & Why They Fail
Penspen
Integrity
1
Pipelines: Safety Record
2
TRANSMISSION PIPELINE: Safety . Pipelines are not dangerous
or unsafe, but their design. maintenance and management
can make them unsafe
XI(I ' _ . .... .
---_ ....
C<>
3
TRANSMISSION PIPELINE: Safety _I f we know and understand why pipelin es fail, we can stop them failing in future!
,... _","-
.
,
2
TRANSMISSION PIPELINE: Environment
.. ----
_~-
5
TRANSMISSION PIPELINE: Environment _M arch, 2006, Alaska - 5,000 barre ls of crude _ The oil spill was caused by a leak in a small section of the 34-inch diameter BP pipeli ne _ BP now under crimina l investigation _ Company/individuals may be indicted ... _ SP chairman (Lord Brown) received reduced bonus in 2005 because safety performance was 'impaired' 6
3
TRANSMISSION PIPELINE: Environment 'The company u id It Is spendin g $12 mil lion t his year 10 fight corr os ion , up from $60 millio n lasl
_ August, 2006, Alaska _ BP commences shutdown of Prudhoe Bay oil field fo llowing a small spill (4 to 5 barre ls).
year .'
_ This action wi ll reduce Alaska North Slope oil production by -400 .000 barrels per day _ BP Chairma n and President Bob Malone .•... the discovery of this leak and the unexpected results of this most recent smart pig run have called into question the conditio n of the oillransil lines at Prudhoe Bay .. o P..--. c""(> 2006
Rovll."
TRANSMISSION PIPELINE: Environment - Oil Spills into Marine Environment (Worldwide) * 60 50
'E
•~
40
~ 30
the amount of oil spi lled in marine waters wcrtdwide" (1990 to 1999) is 943 million gallons (2.9 million ton s)
Exxon Valdez spilled 11 m illio n gallons (257,000 barrels or 38.800 metric tonoes ).
.. . IllS
w
.~
This is eQuiva lent 10 125 Olympic swim ming pools.
20
It was ca rrying 53 m illion ga llon s _
10
o OIL SPILLS O_G......, 2OC£ R. "Si 1
-" '''O S''.
.•_ "'_ "'_",,"-4'"_._'06
'_d"'~_""""'_~"'''
'_0,~
,_
,
4
TRANSMISSION PIPELINE: Oil Spills in USA Onshore Pipelines _Oil pipeline spills amount to about 1 gallon per million barrelmiles (USA Assoc iation of Oil Pipelines).
J
_One barrel, transported one mile, equals one barrel-mile, and there are 42 gallons in a barrel. . In household terms, this is less than one teaspoon of oil spilled per thousand barrel-miles.
6,
9
TRANSMISSION PIPELINE FAILURES:-
Consequences
USA, GASOLINE , 1999, 3 FATALITIES
5
PIPELINES ARE SAFE: Transportation-related
Fatalit ies... Perspective
I_ High w a y .
Oth er
I
6% ====:::-Pipeline (Gas) 1 Pipeline (all )
18
j Rail
1 908
Sea
94%
j
TRANS PORTATION FATALITIES [Iotale 44 ,128)
Air 1998 Data from National Transportation Sa fety Boord and Office of Pipelioe Safely, USA
o
200 400 600 800 1000
TRANSMISSIO N PIPELINE SAFETY: Relative
. Pipelines are 'relatively' safe: _4 0 x safer than rail tanks, and _ 100 x safer than road tanks . From 1986 to 1995 the oil & gas system in USA , accou nted for: _ 63 deaths and 396 serious injur ies. _ In Canada (trans portation safety board ) in 1996: Accidents
Deaths
Canadian-registered aircraft.
408
85
Marin e. Railway.
583 1125
24 107
Pipeline.
27
0 12
6
TRANSMISSION PIPELINE SAFETY: Hazards with Road/Rail Oil Transportation
TRANSM ISS ION PIPELINE SAFETY: 'Involu n tary' versus 'Voluntary' risks RISK
~
~
..,
-~
~ It>PO''"'"'' G"",P ,GOO R. , 611
FATALITIES
Gas Distribution
13
Liquid Transmission
0
Gas Transm ission Highways (1992)
1 42500
Home accidents (1992)
19500
Accidenta l firearms
700
Accidental poisoning
4100 USA Dala - 1993
"
7
LIQUID PIPELINE SAFETY: Latest Data••• cost lEI No of Incid ent s _ Property D amage ( $ M )
250
200 150
,,, •
100
"
"'
50
o 8 6 87 88 89 90 9 1 9 2 93 94 95 9 6 97 9 8 9 9
0
1
us Offoce of PIpeline Safety - all HAZARDOUS liquid hnes ( a s o f Oct 2 006) ~
.
.
.
-
,T
¥
.
-
.
.
, ....~' ... ~ ~_ -,
...-
_"-'--" _ .......... , .~ _ _ • -~-_-----
_ 2
J
4
5
...
"'"
rs
LIQUID PIPELINE SAFETY: Latest Data.•. casualties
I_
Fataliti e s 0 I n j u r i e s
I
40
35 30
25 20 15
-
10 5
o
1t
rill
II JII
71
8687 888990919 29 394 9596979899 0
II
-
.,
12345
US OffICe of PIpeline Salely - all HAZARDOUS liquid lines (as of OcI20(6 )
re
8
NATURAL GAS PIPELINE SAFETY: Latest Data••• cost
1mNo of Incidents
EI Property Damage
I
300 250 200 150
~'h ,
100 ~
H[
50
o
. til
86 87 88 89 90 91 92 93 94 95 96 97 98 99 u s Ql'lioe 01 PIpeline Safely -
0
T 1
2
3
4
-..-- ..
an transmis$iOngas lines (8$ 01 0<.120(6)
_5
NATURAL GAS PIPELINE SAFETY: Latest Data•••
casualties
I-
Fatalit i e s CJ Injuries
30
I
Major inc rease in fatalit ies & injuries in 2000
25
I
20 15 10 5
JIJI
o
8 687 88 8 9 9 0 91 92 93 949 596 97 98 99
1.•,._..
I 0
~IJ I 1
2
n 3
4
5
US Ql'lioe 01PIpel ine $afety - al trnll5l1lission gas lines (as 01 Oct 2006)
---,,-_.
....
._......_.. ,. _c.-.. _.. ".---. _ .11.. . . ,,__,
..__......-..,..............._*"'..... _
"
9
TRANSMISSION PIPELINE SAFETY: W. Europe _ In W Europe, the 200,OOOkm gas pipeline system ... _ had not been responsible for a fatality to a member of the public, in its operating history. until. ..
"' ........01 UfGfttUMnglormln",
---
- " '''''''\1
~=
tl
••
-~
TRANSMISSION PIPELINE SAFETY: W. Europe
""----"'", 10
TRANSMISSION PIPELINE SAFETY: Probability of a Gas Release Igniting ·
Failure Type
Ignition Probability (%)
Pinh ole/Crack
2
Hole
3
Rupture (pipelin e diameter of <16
9
Rupture (pipeline diameter
30
W
)
of > 16
W )
TRANSMISSION PIPELINE SAFETY: W. Europe _ CONCAW E· collates onshore oil pipe lines fai lure data on 36000km of (ma inly product) lines . Pipeline spurs" (greater tha n 1m l) averages 13 per year, mosl very small a Mo st recent ye ar (2004) had 5 spills . 35% of which were ca used by third parties a a eiween 1971 and 2000, a tota l of 5 spillages fro m these lines caus ed 14 fatalities. Four of these spillages resulted in fires
- e.--... ..... ,-, "'"'_
.... lIM (O""!\' _ . " .,-. - d ' 00 _
22 1' Sn.' U
11
t
Pipelines: Why they fail
r \ SP! I
23
PIPELINES FAIL: Due to hostile onshore environments
c: P.......... G_lIlOIl_OlI•
• _ _ .. ~
~ e - -, ' .".. _
"
12
PIPELINES FAIL: Due to Hostile Offshore Environments
"<,
.........
25
PIPELINES FAIL: Variety of Causes
_ _ _ (io&-.g.tIoooo9o _
_
~e-..-
,
....
~'_Qooo_N:CI-... _ _ ....... W_DCUSoO.""'-2OCI
ze
13
PIPELINES FAIL: Third Party Interference 'Third -party damage ... is ... the greatest cause of incidents involving death and injury ..
~
W
_
T
j
_ _ _ ..... _ _
:
_ _ _ "'_000 .CIo_o-
... _ _ "" ... _
..
27
,.,
PIPELINES FAIL: Third Party Interference
---_
.....
What is a 'third party"? ' First party is the pipeline operator.
'Second party is a contractor or agent allowed scheduled maintenance.
to work on me pipe line , e.g. for
•Third party is any person/organization without authority to work on the line. e.g. a farme r ploughing a field and damaging the line :> _
G""CI X!06 1'l0'V6/ 1
28
14
PIPELINES FAIL: Third Party Interference
_.. . . _.. _.. . . . . _ _... . . _._1OIR
PIPELINES FAIL: Third Party Interference
Kenlud<~.
1998
Gas line One ratalfly www.cdc.gov
30
15 •
PIPELINES FAIL: Third Party Interference
Cheyenne. USA , 2006. One fatality
PIPELINES FAIL: Above Ground Impact
A truc k thaI actu ally j ump ed ove r the pipeli ne.
Damage consisted of slight defo rmation and deep gouges but no leak . Repa ired by covering the damaged sectio n wit h repair sleeves.
O _ G _ o 1<.Ol RoW/,
I......... ~ _ -
32
16
PIPELINES FAIL: Above Ground Impact
In lhi$ c.ilMt " . _ 01• lJuck. Ietl lhe ..,.,d , aM hi! lI>It , !)Owl ground pi~
5yna. 1973
PIPELINES FAIL: Corrosion ' _Corrosion can be anything from: _ large areas of corrosion , where no complete pipewal.1_~~ remains , to ... • superficial corrosion, scattered over the pipe
0 ...... .- e:-2OOll_' ........ . .
~
.~.
_ C _ ""CJM.",,
O - , , - _ ..
""._ ..... _ ... , ...,
17
PIPELINES FAIL: Corrosion
Corros ion failures are often 'on ly' leaks, but we do get major ruptures also 35
PIPELINES FAIL: Material Defects (Weld Example)
\8
PIPELINES FAIL: Material Defects (Plate Example)
C Pen Spel'
PIPELINES FAIL: Natural Hazard••• Floods Washout - Argent ina ,
loss of support & protection
J8
19
PIPELINES FAIL: 'Other' Causes••• Vandalism _ 200 1 - Alaska , USA _ $ 17 million clean up, S8 million lost royalties & taxes
R.,.
.._ •.- ...
_ e-_.. . . .
PIPELINES FAIL: 'Ot h e r ' Causes••• Vandalism (cont.) _ A la ska, USA. • 'High powere d" rifle bullet (.338 ca libre ) pe net rates oil pipel ine . - > 1,0 00,000 g allons o f oil leaked ou t. _ Line had previously been hit by 'hunting' bullets, and was 'd e signed' to withstand them . • Police spokesman says '" This is considered somebody und er the inRuerlGe, with a rifle . trying to see if he can't blow a hol e in the pipe line . .... And he 'll live 10 regrel lt."
_ The "per sistent dru nk'was imprisoned (16 years ). s 17million' He wi ll repa y at S10001year. .
. ...,.."""""', ........ """' . .....
&i"'i!0""r.~~~-------~.,
_~ _
..... ..-,,... . '"
20
FAILURE DATA
ONSHORE DATA: USA, 2004
Not. "' at OI' S data <"""96 as cata ;s
"poj.' B<1/'"",_
21
ONSHORE DATA: USA, 2005
""'" th.. o ~s
,... cI",,,,,,, .. d.t. ·,
"""''''OJ",,,;,,,,,
ONSHORE DATA: Gas Lines in W. Europe, 1970-97
W. _ m Euro pe · Onshore Ga s
Pi~line Indde·C"C"C--
CAUSE
Num be r
HoI Ta p By Error
5%
• Hot T"P B y Error
Grou nd Movement
6%
• Groond M"",me "t
Co rrosion
15%
ConstruCl ionJMaterial Defect
18%
Third Party Act ivity
50%
Other/ Un known
6%
o C.on. 'n>el ionl Ma'O
• Tn,,
Total in cidents 945 Freq uency (No/Year/lOOOkm)
-
Actl~I Y
0.48
22
O NSHORE DATA: Liquid Lines in W. Europe
100% , -.-..--
- ...--
-.-..--
-" _ T h ir d Party
90%
80% • Natural Hazard
70 % 60%
• Corrosion
50% 40%
o Operation
30%
20%
10% o%
+-'....-r-r-
~'""-.---'....--1
1971 -
1999-
2003
2003
2003
iii Mechanical Failure
L-"-"=-=--_ - '
2004
. Hol'.....0. ,. "'''" ''' ' ''. "' ,.. c.om_ '" cold h' e, ""'" of the ",,/0(,"'" ,m",,,,,,,,,,,,ot """,,, " """ '0 "'" '''''' 1'''''"," 0"" " ' ''''I "9"'01"". ' at. 0"" '0••,. "'. ,"""""'''''I"O""l ,'osed 00.", '" ""'''9'''' '0"'0000 '......
ONSHORE DATA: Australia ••• Causes' No . of incidents
.
External forces are major cause ID Light ning
1- - - - - - - 0 External Forces • Earth Movement
IIJ Corros ion • Construction
1110
23
O NSHORE DATA: Australia... Consequences ' No. of incidents
'ueiormauonts main cons equence
~
" '-
'0
'"
•
~
Rupture Leak Deform ation Coating damage
~ 0-
lI-
o a/o
OFFSHORE DATA: UK
Causes of Incidents to Operating Steel Pipelines
J!l 0
•
:<1 u .5
0 0
z
• OU-.~ r
o Pipel ine
60 , - - - - - - - - - - - - -- - - - - - -" 0 1 50 • 40 1-- - - 1 l- n - - - - - - - - - - - - - - - ---1 :c 1- - - - - - - - - ---1 30 20 t-10 0
RS"elY moe rser Platform j
24
OFFSHORE DATA: UK ' m
Numbe r «m of ]~O
:. O PF R \ ll O :-;:
· . " U [)D I~
inci dents 300
,,,tJ== =
150
'""
W"
l~O
W" ~II
CO'STRn:-rIO~
O P[ B TI O' -
,"
S""" ,,."'~ t
(""" "" ,"" ,,,",,,,,,,,,", i ;m,..." ~ '
"'"
" " '" as " " ",
ni"" r
-
-=
mu"",,"=
I-
t:
e PM _ " G'W p 2000 Rev6i1
-
E -
·,.. ...,oc<.............._
-...,- ..-- •...,.,. ..__ "' ''''''''.,..... "' · ~ _ · . ~ ~ "-"""'
, ... " ' ~ , " "" " " " , , _ ," , _, UK
"' ~, "" ~_ .
"' ~ _ ~ _ M " ""
_ . " _
....
"~ C ~_
COMPARISON OF USA ONSHORE AND OFFSHORE INCIDENT DATA: Gas
ONSHORE
OFFSHORE
('!o)
('!oj
CORROSION
204
40 .9
THIRD PA RTY
40.4
35.5
CONSTRUCTIO N DEFECT
4. 1
5.5
MATERIAL DEFECT
8 .6
8.2
OTHER
26 .4
CAUSE
'Other' causes are primarily mec hanical compo nents (pig traps, pressure regulators, etc.). fire and operat ional error A GA dal a ( 19R4 1992 )
'
'4 ,
.
"- "
.
25
PIPELINE FAI LS: Different Regions, different failures _ Different count ries/operators have differ ing caus es of failu res, depending on their enviro nment and social structure . _For exam ple, an oil pipeline in China has these failure (leaks) causes over a 30 year period:
30
25
_.- 11-- - -Weld
-
-
-
-------1
O"'Bct
20 Pip ..
15
10
Bod y
I ---~ D'~ "'t_=----,-_o:::::=_-j
0_-5
FAILURE DATA: Trends
26
HISTORICAL PIPELINE FAILURE RATES Pipelines do fail.
Frequenctes can be det er mine d for ons hore 01'I an d gas pipe Imes In the W es ern W orId
FREQUENCY
INCID ENT
(per 1000km yea r) Incide nt Requiring Repair
4
Failure (Loss of Product)
0.6
PERFORMANCE AGA INST THEM, BUT THEY ARE ONLY INDICATIVE l
Failure (Casualties and/or high cost) 0.16 Alberta, Canada Pipe line Fail ure Frequency (1993-97)": Water (fresh and salt) - 11.5 per 1000 km Muiliphase pipe lines _ 7.7 per 1000 km Sour gas pipelines _1.9 per 1000 km Natural gas pipelines · 1.3 per 1000 km Crude oil pipelines . 0.8 per 1000 km
TH ESE ARE 'BE NCH MARK' FIGURES, AND YOU CAN CO MPARE YOUR PI PELI NE
UK data (mainl y methane li nes) give a fa ilure (loss of product) frequency of ; 1960-2000: O.29/1000 kmyear 1996- 2000: O.09/1000 kmyear
.'........ """"""'._ ,,...J .""'"'''''." _. ,_,,.r ""...... ,_ .... ... .... __ ... .... ...-... .,.. " ... .-...'_"""'_A ... r..... " _ _ """.r-., ._"" ...""...,A...... [~,
~ ~
~, ~
~,
w'J" ....
"""'
~ ""'""
...
;oxO r~,_"",,,,,,,,
53
_~ -...
FAILURE TRENDS: In Liquid & Gas Lines in UK' _ Failure (product loss) data from UK (2004) onshore lines (various fluids, but mainly natura l gas): _ The overall failure frequency over the period 1962 to 2004 is 0.263 incident s per 1000 km .year _ The failure frequency over the last 5 years is 0.028 incidents per 1000 km .year
Cl P""""", G, ou p 200ll Rov(i/ l
·'U KOPA "' P." .... fou. Dol..... p .pel " "
54
"'00."" L= loojOOn"
11962 . 200')'
U ~ OP •
. R.""" No"' ,,"' R 8099 ,,.,"'. 1 " .",,1
200()
fN)
27
FAILURE TRENDS: In Liquid Lines in USA' a u ata on 85% of all the inters tate liquid lines (on shore and offshore) in the USA, for the period 1999 to 2204 showe d : _ The petroleum pipe line industry has red uced both the number and vol ume of crude, refined product , and high ly volati le liquid (HVL, e.q. propane) sp ills' , _ Incidents fell by 46% _ Spill volume fell by 50% . Improved testi ng and repa ir techniques , improved integ rity-management practices, and an increased emphasis on managing pipel ine risk have led to these red uctions. e c orrosron spills are the major ca use of spills, but they have conti nue d to decline, led by the reduction in spills from crude oil systems, _ This decline demonstrates the effect iveness of in-line inspection _Third-party damage accou nts for a greater share of o nshore pipe sp ills (15%) than of all spills _ T his damage is also the greatest cause of incidents Involvmo death and injury 'S"". of' - . . '" m"" 'Q ,........~ . , '"w......... ' 0' ''''''''''' ".....''''d '''PO''_'0"...uS "",",,, ~, ",of " ""'0°''''_
_
.
,
s
"
"
"
~
,
l
~
· O... _ ... ,
.
_ Most invo lved farming activities , not traditional excavations <- ~. ""'~- .""~••""" """
55
FAILURE TRENDS: In Liquid Lines in W. Europe' Spil ls/annum
14 ,---
-
-
-
-
-
-
-
-
-
---,
c-- - - - -, . T h ir d Party
12 10
• Natural Haz ard
•
• Corrosion
6 D Operation 4 • Mechanical Failure
2
o 1 971-
1999-
2003
2003
200 3
2004
Spill rate is 0.14" per 1000kmfyear in 2004 co mpared to 0.52 spills per 1000kmfyear 1971-2004
oon' pa '"" '0 0010 ,""" "''''' of tho O'''''''
•• Hof'''''''' O", e h,iI"'.''' 'e ,,'e, ' ,,", ' id'
28
FAILURE TRENDS: In Pipelines in W. Europe & USA' Period
Gas
Oil
Incidents/year/1000km Europe
USA
1970-79
0.76
1.28
1986-2001
0.30
0.55
1997-2001
0.21
0.55
1971-80
0.63
.
1986-2001
0.30
0.48
1997-2001
0.21
0.30
'AMlI""'' ' '" """'" """"."'".. ..",,' " LJ~ ."" ,"""""""""'.... _"'J""''' .,,_W"" "to".." '"""""""",,>ro'"".. ' .........
·Soo ... "" d, ...... , ..
J. ",
2""
dot .......... """""""""" . ._"""'''''.
PIPELINE SAFETY: 'Near Misses'
29
PIPELINE SAFETY: 'Near Misses' • 'If it ain 't broke, don't fix it l ' Is this correct? _ Major acc idents are infrequent. Hence we often have to base our safety practices on limited information; for example, a sma ll database of pipeline fail ures. _ Using 'near miss' data can increa se this database . 'Near misses ' and actual failures may have the sam e ca uses ('common cause hypothes is'), and it can be valid to use 'near misses' to set safely standa rds . 'Near misses' are ofte n ignored as they are low
consequence _ But.. . 'preven tion ' does not have to wail until an accident happens!
E,,,"v. tod,,,,,_ '0 an ..hV'.'" " ""h, • . UK h"n .h" oJ IvMw.h.. 'P' u ~""""' ; ""~" . , ,,,,,, htm
PIPELINE SAFETY: 'Near Misses" in UK Onshore Gas Lines versus Gas Losses 19 %
25%
C aus es of Pipeline Fau lt s (to tal = 1768)
1%
'Faults' are defined as pa,t wall de fects with no gas loss.
4%
'Others' are minor construction damage, e.g. arC strikes or gouges
21 % 23% 37%
Cau ses of Gas Loss (total " 239) 'Others' are sma ll leaks from valve stems and other fittings .
a G ,, ' ~
W. ,d.
. G , u o . " Mo. o m o . ,
1>0' "..
@Pen """ n G"",p2006R..6."
1 3%
5%
60
30
PIPELINES FAIL: Terrorism, Th eft, Sabotage
PIPELINES FAIL: Terrorism' _The oil and gas industry is the target attacked most frequently by terrorists ererrortsts preferred targets: _Government, diplomatic and security forces ;
arransportatron:
.Property ; atntrastructure. utilities and manufacture; _Retail;
.Hospitality, leisure and entertainment.
_ Oil and gas production facilities are 'high value' targets, and often attacked, but these facilities are relatively easy to secure/protect. .Pipelines are difficult to protect, and very easy to damage _ A typ ical attack may involve 2 or 3 terrorists , three shovels, <5kg explosive . a roll of wire , and a battery ' M S'ooo, ,"" ''''''' ol T""on<,," 1'1<>1. P''''' ''OM. M. y 2 00~ pp22_27
62
RBmwo 'kaq', P ·pO" "'Wac ,WoM P' '''" ''''',M . y 2001 0022_3 1
31
PIPELINES FAIL: Sabotage _Sabotage to an oil pipeline in Colombia in 2001 cost Occidental Petroleum $US445 million in lost production.
Colombia's Carte limon oil pipeline has been attacked 654 limes by the National Liberation Army, or .
ELN, since 1986
s..qo,a,C«om o, 1998
~""' 66 ., "' ,m . of " bOl .geo, [ L N)'"
63
~"" ';o .
PIPELINES FAIL: Sabotage
_1973 - Syria/Jordan border. .Typical explosive device damage
32
PIPELINES FAIL: Sabotage •
Iraq: June-August 2003 • Main oil pipeline from the Kirkuk onneios in northern Iraq to Turkey's Mediterranean port of Ceyhun . • Iraq losing $7mililion/day due to this sabotage
PIPELINES FAIL: Sabotage • Iraq: August 2003 • Water pipeline • Sabotage suspected. • 300,000 Iraqis withou t water
66
33
PIPELINES FAIL: Theft
- Theft is a major cause of 'failure' in many pipelines around the world. _T he illegal taps can be sophisticated and difficult to detect. _ One approach to reduce theft is: . Patrol your pipeline at areas of high risk (e.g. nea r village s or local criminals) _ Work with police 10 destroy the 'organised' crime (ma ny of the thefts are for a criminal with a organisation selling to custom ers). _ This will requi re special detective work. _ Review internal staffing (often criminals are working with pipeline staff)
PIPELINES FAIL: Theft _ Theft in poor regions can tak e several forms _ Small scale, local opportun ist theft _ This is usu ally local theft, for local consu mption, by 'amateurs'. Usually highest consequences.
_ Small scale . local compensa tion claim _ Driven by compensation gains (food, farming , eIC.) fo llowing a deliberate leak _ La rger scale , product pipe line theft. local organised cr ime .
Example of the 'cost' of th eft, In
Nigeria : Dec 2006: >260 killed In Lagos
May 2008 : >150 killed in Lagos Dec 2004: >20 killed in Lagos Sept 2004 : >60 killed in lagos June 2003: >105 killed in Abie State Jul2000: >300 killed in Warri Mar 2000: >50 killed in Abia State
OCt 1998 : >1,000 killed in Jesse _!IIlC. "'~Z'"
a c en fill road tanker _ La rge sca le crude line theft. org anised crime
e c an be int ernati ona l crimi nals. Valved fittings used. Can fill oc ean ta nker Cl ~c......2005_'
68
34
PIPELINES FAIL: Theft
April
May
"
_
200 killed in oil pipeline blast
PIPELINES FAIL: Theft A ne w report in 2000 stated that ... the Niger-Della region has recorded the deaths of about 5000 people from oil pipeline vandalisation and e xplo sions in 2000. The president of the National A ssociation of Niger-Delta Professio nals, Mr. Mietanuno Jaja , said the deaths and destruction of property worth millions of naira resulted from 781 cases of veraeuseuon and 82 cases of e xplo sions of oil pipelines in the re gion. ~(>V
Cans left by those who burned to death
10, 2000, AIlAfrica.com
35
EXAMPLES OF PIPELINES FAILURES: USA
National Transportation Safety Board"s Pipeline
Safety Hearing 2000 . 1. _ Over 2.1 million mi les of pipelines in USA . _ In 1999, USA pipe lines de liver ed" _ 13 bill ion barrels (55 8 billion gallons) of petroleum products, such as crude oil , gasoline, diesel fue l and heating oil, to customers _ in addition, the number of customers using natural gas in this country has exceeded 60 mi llion . • 'In... 30 years . we ha ve seen too many tragedies or near-tragedies that were all caused by the same fundamental problems ... This... safety hearing (will) address two of those problems . p ipeline inspection and integrity verification _ leak de tection and response.'
Edison 72
36
RECENT ONSHORE FAILURE: USA, 2000
Gas Line. Unpigg ab le. 12 fatalities. 86ft crater, Internal corrosion (m icrobe s). du e 10 poor COITosioo COI1tro1' I.:;,...;;';Si:':~ No pig cleaning runs,
RECENT ONSHORE FAILURE: USA', 19905 7million lor damag es Gaso\al'\El: • 1 year old M&Chanica1damage Oller
Gramercy. Louisian a
Reedy River, SOUlhCarolina
"'P._.., _-_... . .._ - ....- ,.. . . .4. _ .._ -.... ___ __ . . . . _' . _ ~
l ... .. _ P ""'....__ "O"'·_'.'-"'Ib """ ~"""'"
~
37
RECENT ONSHORE FAILURE: USA' , 19905
Gaso\el1e: $16m'
11\00 lor damageJclean-up D5AW seam weld edge
COfTosiOn-f a\igue on
Oiese1: Slmi\\ionlor dama9"'rll6P'plI CO'fOS\oI'I in low \Oll9hll6 SS \
Knoxville, Tennessee
Chalk Point, Maryland
75
RECENT ONSHORE FAILURE: USA', 19905 _ Many of the hazardo us liquid and natu ral gas transmission pipelines in the USA are 30 to 50 years old . _ Bellingham was constructed in 1966 e c eaeceo. New Mexico in the early
195Os. • 'AI/hough age alone does not indicate fha/ a pipeline;s unsafe. it does make determining the integrity of pipelines increasingly important.' ..
NTSB
Winchester, Kentucky
38
PIPELINES ARE GETTING OLDER••• and this can happen••• so•.. DON'T BECOME COMPLACENT!
-n
ADDITIONAL INFORMATION
C """""", C "",,, 2OOII _
'
39
TRANSMISSION PIPELINE SAFETY· Risk Assessments _ The goa l of a risk assessment model for pipelines and. specifica lly. pipeline accidents, that is implemented in a project, is to determine a methodology by which 'end-of-pipe' strate gies can be com pared with the implementation of preventive measure s to determine which strategy prov es more cost effective. • 'End-of-the-pipe' techniques mean that once an accident or incident occurs they have technology and a response system to deal with it. _ The cost s involved in an accident are the direct costs including property dam age, lost product, fines and clean up cos ts, as well as other intan gible costs related to cor porate image , loss to competition etc . _ This accide nt cost is multiplied by a coefficient representing the risk connected to the accid ent. the product of whic h is conside red the "risk relative cost " of the accident. _ The total costs of two strategies can then be co mpared.
79
TRANSMISSION PIPELINE SAFETY· Risk Assessment _ Preventive me asures, as opp osed to end-of-the-pipe tech niques, are implemented before an acci dent occurs and active ly work to reduc e the probability and consequences of an accident. _ Different types of preventive meas ures include preventive monitoring , and advanced technology. _ Introducing such measures work s not only to reduce the risk of an accident occurring but also the cost of an accident if it occurs _ Liabilities and fines are often lower, reclaiming can be easier and cheape r, and repair action is more likely to be minor. _ Different parts of the pipeline ca rry with them various risks dependin g on outside influences, so il type, etc. Th erefo re an effective risk assessment procedu re will take into account the differing aspects of the diffe rent pipelines. _ This is accomplished by section ing the pipe line and then performing different testing procedu res on the various pipelin e sections .
40
TRANSMISSION PIPELINE SAFETY· Environmental _ In all pipeline failures, there are also the less quantifiable/tangible costs , such as corporate image and loss due to stopped service. _Shell, for the outcry of the Brent Spare case, temporarily reduced its market share in Germany in the following month by 30%. _Obviously there is also environmental damage, the extent and type of whic h depends on size of the acc ident , type of soil, population density, etc .. _ The EPA has a system for damage assessment used in the NRDA (Natural Reso urce Damage Assessments ) regulations, based on measurable adverse changes in the physical and/or chemical quality of five major types of natural resources: suriace water, groundwater, air, geolog ical and biological.
81
TRANSMISSION PI PELINE SA FE T Y: Environmenta l Ri sk A ssessment _Risk assessment attempts to take all the environmental variabl es and all the environmental costs into consideration. _By using risk assessment, a company can determine what types of preventive measures are worth pursuing depending on how much they reduce the probability or consequences of a given incident. _The extent to which they clean-up, report, reclaim and/or repair depends on the liabilities and environmental regulations of the specific cou ntry towards that specific industry as well as the individual policy of the firm.
a one of the
goa ls of risk assessment is to encourage the implementation
of preventive measures.
41
TRANSMISSION PIPELINE SAFETY· $ Costs
_ When an accident occurs, there are high costs. Acco rding to 'CO NCAWE', in the years 1971- 1986 there were _ 430 pipeline incidents which caused
_ 26 deaths, 149 inju ries and _ $18 million in property damage. _ A single accident in 1997 on a pipeline carrying petrol
caused 5500,000 in property damage as well 1,200 barrels of lost product.
_I n 1997 an oil and gas pipeline accident caused $224, 000 worth of property damage . _ O ther costs include fines and restitution. 0_0..-2001;_,
83
TRANSMISSION PIPELINE SAFETY· $ Costs _ T he Office of Pipeline Safety, USA was formed in 1968 to establish gas pipeline safety standards (requlations).
_ In 1992 their remit extended to liquid lines and environmental protection _ Over 400 people work on their safety programme _It has a federa l budget of 547million (200 1). _ $- 3m illion is spent on resea rch
_ Pipeline operators pay $85/mile (gas lines) or 574/mile (liquid lines) to fund the safety programme
42
TRANSMISSION PIPELINE SAFETY· $ Costs _On January 1, 1990 an underline pipe connecting Exxon's Bayway Refinery and a nearby term inal ruptured and released over 500,000 gallons of refined oil into the Arthur Kill, a water body separating New Jersey and New York. _ The spill affected several miles of shoreline and killed hundreds of birds in the area . The settlement totalled a $15 million cost to the company over a five year period. Payments included: .$10 million for "environmental initiatives" including the purchase of new wet lands, _$4.8 million in restitution to the governments of New York and New Jersey and a _$0.2 million crim inal fine.
TRANSMISSION PIPELI NE SAFETY · Costs
_ In a recent survey by INGAA, USA interstate natural gas pipelines spent $560 million dollars per year on safety for approximately 160,000 miles of pipeline. _ That translates into $3,5 15 per mile of pipe.
86
43
PIPELINE FAILURE RATES - Statistics can be confusing....
..
--"""'- --,...
-
.-
.
i
-
- -
...-.
,
Criteria w as changed
-
0
- 1- - - -
•0
.. '...
./' .,::' ~<",;.' ,~"
,~~ ,•.f' $' .,~ #0<"
ilnnmumhLJ
.tI'~',,J) ,,',. ." , " ;,.i .'." ,'#";"
USA OffICe o! Pipetone Safe ly Da ta
COMPARISON OF ONSHORE INCIDENT DATA
C A U SES
US GA S
EUROPEAN GAS
CAN AD A
US
EUROPEAN
GAS
0"
0"
HU NGARIAN OI L & G AS
THIRD PARTY
404
282
12.6
21.5
47.5
565
CORROSION
,.,
15 1
11.6
21.7
27.7
11 ,6
12.7
95
3"
1',5
12,9
OPERATIONAL ER ROR
26.4
46 .5
41,5
45.4
'" "
INC IDENTS/ l OGO kM YR
0.26
1.85
2.93
1.33
0.83
4 ,03
MATERIAl AND CONS TRUCTION
-
-
DEFECT
129
AGA dill" ( 19&1_ 1!i>l2)
0: _ _
1OOlI_-'
ee
44
TYPICAL PIPELINE FAILURES & RATES
O)[J]',TRY
:\,WOI{ CAUSE OF FAILURE
USA (Onshore gas) USA (mshore gas) USA (Onshore & Offshore oil
Western Iurcoe (Onsbore gas) Western Eurooc (Onshore oil) lfunaarv(Onshore gas) Poland (Onshore gas) as (Onshore gas) Czechoslovakia (Onshore gas)
FAILURE RATE (DCr 1000 km war)
0.16 0.70 0.56 0.6
External Intcr fcrcr cc Corrosion Exter nal Interference External Interference Corrosion Girth Weld Defects Corrosion Construction/Material Defect Construction/Material Defect
O.X 0.1 0.08 0.33 0.13
LATEST ONSHORE DATA - OILIW. Europe (1991 2000) 50
./T---C==~~~~------
119 Cold
lines I
40 J/le=
30 20
10
Th ird
P ~ .ty
Nat .. , ,,1
C o ""a l o"
OperaUoaal
Mechan ic .. .
e Poo"""" G"", P lOO6" ",,61\
HOi lines experience many failures due to external corrosion
90
45
LATEST ONSHORE DATA - OILIW. Europe (19702000) - TYPE OF FAILURE
%
35
30 25
20
PIiIhoIe "Jess lhan 2mmx2mm nss.Jre .. 215..15,mu/O'%ma.. wide
' 90% of all pinhole leaks are caused by conosion
Hole '" 2-
15..75mm.t ~trlltl wide
·Corrosion
SpJir = 7~ 1000mm long If 10% max wide Ruptur e " :>75mm lo ng If 10% min wid e
causes on ty 18%01 rupt ures and 30% of splits
15
-Third party
10
dam age causes 52% of ruptures
5
0' --
S p ilt
Pinholes give the smallest spillages, ruptures the largest
st
THIRD PARTY INTERFERENCE· 'Malicious' Damage In 30 years, the Western European Oil Pipeline System (31,000 km) has had 10 spillages ca used by third parties (only one attempt was on a buri ed pipeline - the others were on above grou nd sections, or valves. etc ..)
CAUSE
NUMBER OF SPIL LS
Terrorist Bombs
2
Vanda lism
5
Theft
3
Totals
10
GROSS SPILLAGE (m3 )
NE T SPI LLAG E
2597
1716
(m 3)
92
46
TRANSMISSION PIPELINE SAFETY· W Europe _ Fatal Incide nts :
1971-2000 5 spillages (4 fires)
14 fatal ities
_ One fatality was caused in one theft att empt, with no ignition _ A thief dug a pit to expos e and drill the line and could not esca pe the pit as it filled with product _ In all but one of these spillages , ignition was hours or days after the detectio n & demarcat ion of the spill are a _ The spillages them selves did not cause the fata lities _ Mosl fatalities were to work ers aro und the spill. or bystanders
93
LATEST ONSHORE DATA· OILIW. Europe - We can control corrosion in old (cold ·) oil lines 0.25
I_ Oil
Lines
-No increasing trend up to 45 years old ·Hlgh incidence 01 corroslon~ ~!Oad
crossings. anchor pomts . sleeves, etc..
a.
0.1 -H---t .
- -U- -......- - -..- -- - -1
(/)
0.05 +r-;
0 _5 6 ·10 11 _ 15
("hot oil lines are
~ 16
In 16 _ 20
21 · 25
26· 30
3 1_ 35
36 · .0
. ,. 45
4650
51 _
56·
6 1·
~
eo
ee
66· 10
more likely to fail by (eKlema l) corrosion )
47
LATEST ONSHORE DATA - OILIW. Europe (1995)
CAIJS E
NI ;\IRER
A'\NLJAL AVERAGE (1991-95)
ANr\l },\L AVERAGE (19 71-95)
r-.1ccha nica l Fail ure Opera tional Corrosion Natural Hazard Th ird Par ty Acnvitv
5.2
38%
3.5
I 2.6
7% 19%
I 4. 1
04
3% 31%
Tolal
4 I I 0 4 III
Frequency
0.33
0.6 4 .5 f3.7 0,64
4.2
13.2 0.43
25% 7"' 30% 4% 33%,
'"
In o / r<'ar / f f}(Jln m)
Mechanical failure (e.q.Ila nqes]
co nstruction faults (Inc, dents from construction) & material failure
Op e ral ion al - hum a n e rro r, et c __
Corros ion - mainly externa l corrosion Natural hazard - landslides, floods , etc Third party - includes ma licious It>poo""" Group 2000
f(e,(>"
COMPARISON OF CANADIAN ONSHORE I N C I DEN T DATA, VARIOUS PRODUCTS N. Gas
Crude
W ater c""~
"""'..,.
_. ,~~~., ~ 17 0"<,
'"
\
-> ITlalnly intemalrorro';on
. _..•
I
~
Coo,,,,"
72 0'"
AI/;>or18. Can ad a 1 99 1 ",prese nting 208. OOQltm 01 O<1snoro p ipel" ",,s
48
CANADIAN GAS PIPELINES (ALBERTA EUB DATA)
,.
,, '. L
---- ----- - --
.
•
.'
, • , : • •• • , , . • •, , , , , , ,,, ,, • • , • ,, •, ,
_... ·· . ·· ·· · •• ·" , · ,, ·, , ..l-.-..,.---"" · · , ", , ~
,.
~,
•• • • ,
•
·, ..· • •.,, ·...---... -. • · • ·,, •· .. , ·•· ,", , , ·· ·· "
TRANSMISSION PIPELINE SAFETY· USA Fa ta titic s, USA_Gas I H lf
14 -
• Onshore . O ffsho re
12 10
8 b
4
• ,I
!
o•1 ~
0_
Go:Ioc>2OO!i _ '
M ~
II ~
~
~
~
~
~
•
= x
I N
x
~
x
~
x
.
~
~
•
II I • I•• = ~
N ~
~ ~
~ ~
98
49
Offshore Spans
"
,. "
===~o,
Data Source: UKOOA 1998 (From revie w of 293 pipelines covering 7,811 krn. Tota l of 33,482 spans, approximately 14,164 had a length greater than 10m and 98% had a height less than O,5m)
Danger from Excavations * If you are excavating, and there is a chance of unde rground pipelines: . Always chec k for the presence and location of pipel ines before the start of any construct ion or utilities wor k If in any doubt always contact the pipeline ope rate' _ If a pipeline is known to be present con tacl lh e operator as soon as possible and arrange for an on-site assessment. This is best done at the desi gn stage so an informed discussion on des ign, working practices and use of equipment can take place, _ Take reasonable steps to verify any pipeline location info rma tion g iven to you and don't re ly on it alone . _Make sure everyone invo lved in the wor k und erstands the importance of avoiding pipe line damage and of reporting any nea r misses , especially if it involves surface or coating damage to the pipe line
c
p~
G
R", &' 'Av_
100 _
rS BN 071
'"' 7440 1000 f mmht< r :li.......
~, rom.'Boc"
'N)
50
Introduction to Fracture Mechanics
Penspen Integrity l,;;~~~:=;
1
1 . FRACTURE MECHANICS - PERSPECTIVE & BACKGROUND
«1_2001"-'
z
FRACTURE MECHANICS •
•
Fractu re mech an ics pr o vides us wi th the sci ence and models to un derstan d the beha v iour o f defe ct s in struc tu res II is used extensively
•
It fOfms the basis of all the methods we use in pipelines.
•
However. we have d ev elo ped our own methods ove r the years . wh ich hav e ta ken the complexity out o f the ca lculations.
•
B ut they are still base d on fract ure mechan ics
PERSPECTIVE 1 Fracture Mechanics a
SCience
General Co(Nicatl(Jn In Pipelines
cooes Specific Guidelines
I
I S8 179 1011 API 579
I
ASME B31
II
AP 11104
IASMEB31GII CSAZ184
I I
p NV OS F1 0 ~ p NV RP Fl 011
Best Prac'ices : I ASME B31G I
Corrosion
I
Gouges
Battelle
I
Girth Welds
I EPRG
I
Crack P rop.
I
EPRG
I 3
FRACTURE MECHANICS· Perspective •
FIRST..• GOOD D ESIGN ! - All eog lneeml9 structures should be desiqned. built and operated 10 a recoqmsed cod e o r stand ard, •
•
•
•
Occaslooally, detects occur in these structures. and I'acfure mech aniCScan be apph~'Ilto these oerccts to determine the StruCtUfC 'S neess purpose FRA CTURE MECHANICS IS NOT A SUBSTI TUTE FOR GOOD DESIGN, B UILD OR OPERATION - IT IS COMPLEMENTARY
'or
ASS ESS ALL POSSIB LE FAILU RE MODES - When a pplyin g f ractu re me ch a nic s to de fect s, all potc nnar fai lure mod es shou ld be Ide ntifi ed , Ty pical fai lure modes to be con sid e red mcruoe •
F,actL.r&
•
Fatigue
•
Yie lding Of plast ic collapse
• • •
lea kage Corf'OSlOn and crcson Stress COITOSIOO crading aoo COrr05'On la~gue
• • •
Buckhng Creep and crecp,1abgue Often. a combtnatlOO 0/ 'al lu'e mooes -eees to be eceeeerec.
We will deal W1lh rracn. re . pla stic coll apse a nd fatigue in this pr esentation
,
FRACTURE MECHANICS - Warning • NEVER ASSESS A MESS! - Fracture mec hanics can help you assess defe ctive structures. but you should not app ly it to structures that are d early unsafe . or have been badly designed . built or operated.
5
WHY DO WE ' N EED' FRACTURE MECHANICS? NO DEFEC T: "0
"0
o
.Q
ctl
U lto m~ t~
ctl
, e;'c strength
Ul timat e tensilQ stro ng tl1
t
: t<.. "Yield streng th ••
..
•
We -:lesogn' ".... .:rue' .r... if> tf"o> ' 'Y''''. t...: a .oe\e<:: -f,.... """"""'" .... laor"' ...... "'90"-. _ ~ >ltesses '" .,.,.,. 1<1_2UJ& ...... '
.,
)GO
Fail ,~
Failure
' .,L-
'1_.
""......... _
. .
.
,
5- ....... ...
oeted;" t!">e ........ ~ .. , <\ _
s:<,,;r.s- _
I...
M
.
--'
'*'1\ס0lII
- . . ,." "'"- _ _
6
THE FIRST FRACTURE MECHANICIAN? e t eonaroo da Vinci (1452-1519 ) tested iron wires of various lengths: _ He failed a long length, then tested half of the remaining length . _ He noted that this half length failed at a higher load _ He then tested a half of the remain ing length (f e. a quarter of the original length) and noted this quarter length had a higher load than the full and half lengths. _ Drawn wire in the 15-16'h ce nturies will not neve been good & regular quality. t.e the longer the length, the mor e likely it was to
Drawn wire Full Leng th
Half Quarter length length
load
contain a defect e rneretore the longest wire failed at the lowest load because it contained the largest defe ct
:<,_
2IXJi _ .
r
BACKGROUND TO FRACTURE MECHANICS· Notches .The conventional approach to des ign is to consider the loads acting on the structure and the tens ile properties (yield strength, tensile strength) of the material. .This approach is not val id if the struc ture con tains sources of stress conce ntrations (e.g. notche s) or defects (e.g. crac ks).
1_1. ~
I
r...,... St,.....,." l'o4'ld Sl''''''9'!I
_ The presence of a notch or crack can reduce the failure stress of a structure to a very low level (i.e. well below the yield stren gth of the material containin g no defects ).
1<,_
2OOlI 1I__'
..
_--_...----
8
BACKGROUND TO FRACTURE MECHANICS· Notches _A defect is a source of a stress concentration. _I n a ductile mate rial, plastic deformation occurs whic h leads to a redis tributio n of stresses, blunting the crack and removi ng the stress conce ntration . • However, in a brittle mate rial no redistribution of stresses ca n occur.
,
~
• Fracture mechanics is a framework for estimating the stre ngth of a material in the presence of a defect . Fracture mechanics desig n parameters include: toughness, yield strength , applied stress, defect size, temperature , stress state and the load ing rate . (e) po, ,,,,,,' 2M Rovo;l
9
BACKGROUND TO FRACTURE MECHANICS· Inputs MATERIAL PROPERTIES (FRACTURE TOUGHNESS , YIELD STRENGTH , etc .)
A DEFEC T SIZE . . . . APPLIED STRESS
BACKGROUND TO FRACTURE MECHANICS - The Mechanics
6
_ In applied mech anics we load a structure , and fIIIATEIUAl PR OPERTIES we need a mea sure of the stress in the (FRACTURE TOUGH "IESS . YielD STRE~GTI1 • • 1e I structure caused by this load. This load could be a press ure in a cylind er. _ We the n compare this load to the rnatenars resistence to the load (its yield strength) , _ We then need an equa tion that link s this load for a and resistan ce fo r failure conditions, cylinder under pressure, failure occurs when: . yield stress = PD/2t
e.s.
DEFECT SIZE
AP PLIE D STRESS
_ II is similar in frac ture mechan ics . • {Va ne ed a measure 0' the driving force £II the crack. lip.
caused by the remote oacmq • !J e need a measure 0' the ma teria 5 resi stance to ttus driving force :::15 toug hness} . ....00 'i na Iy we need an equation that links this load and resistance, to qrve us a fai me condition
n
BACKGROUND TO FRACTURE MECHANICS - How Notches Raise Stresses . Notches/Defects do two things to a structure: _REDU CE CROSS SECTIO N - A notch or a defect in a stru cture certainly reduces the structure's fa ilure stress - as it reduces the cross sectional area and hence the load bearing capacity, _CONCENTRATE STRESSES · Unfortu nately, these defects also concentrate stresses at their tips or bases , and failure can occu r at stresses well below a conventiona l des ign stress , and also cause premature fatigue failure s, _ W e will look at the effect of both : enotches' (relatively blunt defects, that create a stress conc entration) , and . 'cracks' (sharp defects that create stress intensi ties) _ We will start by considering notches, as they are the sim plest and best unders tood 'stress raiser' in a structure
----
tz
BACKGROUND TO FRACTURE MECHANICS· How Notches Raise Stresses
stress > f0fceIar ea
_ W hen I apply a tens ile stres s to a plate, I have a unif orm stress aero 5S the cross section - a uniform 'field'_ If J introduce a fea ture Ihat distur bs the stress fields , they becom e conc entrated around the fea ture - this is called a stress concentratio n.
raise~
_ For example. a simple hole can stresses locall y by a factor of three
_ The sharpe r the featu re (e .g. a crac k), the higher the stress concent ration. _ These stress concent rati ons can lake the material ne xt to the feature to a stress nigher than the yield strength of the material . and cause failure if the stresses ca nnot be 'relaxed', e .g . by plasticity. 1<1 _1CIlI _
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EFFECT OF NOTCHES - Differing Concentrations _ Notches create high stresses in a ma terial. _ T hey 'concentrate' the stresses. . W e can calc ulate, measure , etc ., the se stress conce ntrations. _ Consider an ellipt ica l hole in an infinite plate . _ T he m ax . stress at the edge of the hole is : _ S,,,,,,= S(1+(2b/a) _ If aeb, and we have a circular hole, then S"",, = 3S _ Note two other features of this equation : _ If I reduce a . my ma x. stress become s very large. _ this is approximating to a crack stress nero . _ If I red uce b. my max stress redu ce s and eve ntually become s equal to S 1<'_ ...... :>006_"
Stre ss, S = force/area
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/i Id inile pl~ le
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1 So,.. as I decrease za. my notch becomes a crack and my stresses become infinite'
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EFFECT OF NOTCHES - Stress Field
Stress field
Stress conce ntration = K
BACKGROUND TO FRACTURE MECHANICS Failure Modes OUC TILE Slow controlled extension; final ins tabili ty due 10 large reduction in area , Cup -andcon e failu re surf ace charact eris ed by 4 5" she ar lip
BRITTLE Fa st ca tas trophic failure with no warning Transverse 9ra n L; ~a r
cleavage surfac e - no she ar lip.
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BACKGROUND TO FRACTURE MECHANICS Ductile To Brittle Transition, & Toughness
_Two material properties that are of key interes t to us whe n we are assessing a struc ture's fracture resistance are: _ T he 't rans it io n' temperature of th e m at er ial _For example most new structu ral steels will fail in a ductile manner (large deformations preceding failure) at temperatures above OOC, but fail in a more brittle manner (low deformations preceding fraclure)at lower temperatures. _ The 't o ug h ness' of th e m at erial _This g ives us a measure of a material's resistance to defects, l.e. the higher a mate rial's toughness the higher its tolerance to defects
2. DUCTILE TO BRITTLE TRANSITION
BRITTLE (CLEAVAGE) FRACTURE AND DUCTILE (COL LA PS E) FAILURE •
In simple terms. failure can be considered to be the resu lt of two compe ting , but related . mechanisms, nam ely brittle (cleavage) fractu re and ductile (plastic ) failure
•
Bri ttle fracture is related to toughness and ductile fa ilure is rela ted 10 the yield streng th and the tensile strength ,
•
Line pipe steel is usuall y lough and ducti le, and therefore. only the tensi le prope rties need to be considered (failure is 'independent" of Iouqhne ss).
briNfe
ductile
BRITTLE FRACTURE •
Brittle fracture is a rapid cracking through a stress ed material The cracks usuall y trave l so fast that you cannot tell when the material is about to break, 1.8. there is very little plastic deformation before failure occu rs. e .g glass • Gene rally, berne fracture is the worst type of fracture
•
In brittle fract ure, the crac ks run close to perpen dicular to the a ppli ed stress .
because jl occurs wll hou t warn ing , and IS 100 rapid 10 slop.
•
This perpendicular frac ture leaves a relativel y nat surface at the break .
DUC IIL ~
Stress
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•
20
DUCTILE FAILURE •
•
Ducti le ma terials fail with large amounts of plastic deformation while brittle materials sho w little or no plastic deformation before fract ure •
the crac k moves slowly and is accompanied by a large amo unt of plastic de formation.
•
The cr ack will usually not extend unl ess an Increased stress is app lied , but bnltle fractu res, cracks spread vefY quic kly wilh little deform ation
A ductile failu re starts with plast icity at the crack tip •
•
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Then sma. mlCtovolCls /orm around al'ld ahead of the cmck _ DelomlabOn continues and !he
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Tile tlf!W fra<;llJre SU'iace ha s a very lI'fe9u1ar appearal'lce
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DUCTILE TO BRITTLE TRANSITION •
The mechanica l properties of a steel vary with temperature: • Tem p (C) Y ield {MPaj UTS (MPa) % Elongation
• 40 0 • 200 • -60
• •
•
500 600 700
820 920 1000
26 22 21
Over a sho rt temperature range , it will fail at similar stresses and strains , if it is defect free This is not the case if we hav e a notch in ou r ma terial, The ma terial can: • Fail at lower loads as the temp erature rero Strength dec reases • Exhibit differen t fail ure characte ristics (ducti le or brittle failure) Some materia ls undergo a trans ition from ductile to brittle behaviou r, und er cond itions of dec reas ing temperature, or incre asing loading rate •
Most glassy materials and some engineering materials such as mild steer show this transition .
Temperat ure
ea
DUCTILE TO BRITTLE TRANSITION •
Materials thai undergo a fracture transition are those in which the yield strength rises sharply with decreasing temperat ure • Some mate rials have a transition ... body cen tred c ubic materials (e.q . mild steel or 9% nickel alloy ) • Some ma teria ls do not have a transition .. . face centred cubic m aterial s (eg . alumin ium o r austenitic stainless steel ), which generally do not have low yield strength temperature sensitivity. neve r undergo a , fracture transition. • Three basi c factors contribute to bnttle fracture: ield Strength ~ • triaxia l stale of stress (e.q. a notch ), low temperatu re (i.e . below the t ransition tem perature ), and a high strain rate .
---,
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c::::::> •
c:::::::::> •
Temperat ure
DUCTILE TO BRITTLE TRANSITION • The ' Da v id e n k ov Diagram' Yie ld Streng th (hig h stra in rate or
Stress
Stram Rate (m .s' m)
~a,ned ge~
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Y;eId (MPajU TS l,,"' Pal
200
400
zeo
380
320 530
430 550
~---
Fracture Strength
L-
Yield Strength
_
Temperature
The material is considered to fail under two compe ting matenal ceccenes : yield strength ancl brittle fracture strength. The theo retica l Iracture strength in many tunes greater than the measured fract ure strength due to the presence of micro cracks both internal and external "J""_.IlJUIR~o;. ,
24
DUCTILE TO BRITTLE TRANSITION - Effect of Temperature fcc ma terials
DUCT ILE bee ma terials (low streng th)
T RANSITIONAL
high strength mate rials BRITTL E Temperature 25
3 . TOUGHNESS
1
TOUGHNESS •
Th e failure of a brittle ma teria l is prec eded by very little (o r no ) plastic deform ation = 'low' to ughne ss.
•
Th e failu re of a ductile ma ter ial is preced ed by significant plastic de form ation = 'high' toughness .
•
Tou ghnes s is a mea sure of a ma te rials resista nce to the pres ence of de fects .
•
We use toug hness to:
Stres s
• Give us a measure of a ma terial's resistance to defects • In fractu re mechanics calculations to calculate failure stress of structu res con taini ng defects
Strain
_nof_'
< ......
TOUGHNESS •
We know that in some mate rials . as we decrease te mperatur e. th e toughnes s of the materials decreases. • This means the ma terial will only be able to tolera te smaller defects as the temp erature decreases .
• •
We also know that so me materials are 'to ugher ' tha n ot hers (co m pare stainless stee l, to a glass) W e ne ed to be able to meas ure toughness in a material. We can do this in two ways: •
Q ualitative - th e toughn ess w ill have littl e a bso lute me ani ng , bu t have so m e re lati ve or quality control meaning • This is the easiest measure of toughness and is used In many irdustnes as a simple GLoality COO!rol measure , but It has been used 10 help prevent s1nJctural failures
•
Q uantitative - the to ug hne s s will have a n absolute v alu e , and we can use this in fracture mechanics • Ttus is more complex, but will allow us to actually predict the failure stress 01a defective structure We will deal with quantitative toughness laler .
QUALITATIVE TOUGHNESS • • • •
•
• •
In the 19'h century it was recognised thaI fracture and fatigue were influenced by the presence of notches or cracks. Notched bar impa ct test ing of iron and steel was used & established by the end of the 19th century to indicate the ductile to brittle transitions in steels This allowed more und erstanding about fra cture in materials . We knew that if we: 'OW:T\JotE T~" • Have a triax ial stress field (a notch ) • A high strain rale (e.g . impact load). and D. . .C 'SllE . ......IOtTRU$ • A low temperature, We could fail a mate rial very easi ly, unde r very low loadi ng. Hence , impa ct specimens conta ining notche s could tell us som ething about fra cture and resistance 10 fractu re. The great thing about these speci mens is that they cou ld giv e us inform ation to help us model fullscale beh aviour W e can expect materia ls with both hig h strength and high toug hness to withstand high impac t loads 29
QUALITATIVE MEASURES OF TOUGHNESS (SMALL SCALE IMPACT TESTING) • Qualitative measures of toughness, based on impact testing of notched specimens, were developed before the introduction of formal measures of fracture toughness and fractu re mechanics test specimen s. • Exam ples include the Charpy V-Notch Impact Test, the Drop Weig ht Tear Test and the Izod Impa ct Test.
• These qualitative measures of toughness can be calibrated against the behaviour of a structure, but, in isolation, they will not necessa rily be representative of structural behaviour (i.e. necessary to correlate small scale specimen behaviou r with structural behaviour).
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QUALITATIVE MEASURES OF TOUGHNESS Charpy •
•
• •
The Charpy V- Notch Impact Test is the mos t commonly used of these qua litative measures of loug hness for line pipe steels . It is a 10 mm square cro ss sectio n of the material, with a 2 mm dee p, 45 degree V notch in the surface . The specim en is impacted by a pendulum, The difference in height gives the ene rgy absorbed
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QUALITATIVE MEASURES OF TOUGHNESS Charpy •
The energy is abso rbed in the initiation and propa gation of a flaw , and in the deformation of the specimen. Remember __ toug hness under static loading is higher than dynami c,so dynam ic loading is a sev ere le st of a material's toughn ess
32
QUALITATIVE MEASURES OF TOUGHNESS Ch arp y
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33
QUALITATIVE MEASURES OF TOUGHNESS Charpy Energy versus Temperature Cha rpy v -Nct ch Im pact Ene rgy Ener gy Absorbed
upper shelf (DUCTILE)
100 percent P i~ cl , ne steers \lS LJ~ l l y ope-ate on \111 $ 'upp er" shelf, and so are ductile
---
a percent
lower shelf (BRITTLE)
Tempe ra ture l
Percc-itaqe Cleavage Fractu re
QUALITATIVE MEASURES OF TOUGHNESS Effec t of Specimen Size
-
upper shelf (DUC TILE)
Energy
lo wer shelf (BRITTlE) Temperature
• However, there was a big problem w ith these small impact lest results.
• The ductile to brittle transition could be raised by increasing the lest bar size . • This had serious implications when app lying the results of the sma ll lest spec imen 10 a larger structure
QUALITATIVE MEASURES OF TOUGHNESS· Charpy versus Structural Behaviour Struc t ure
Energy Absorbed
Charpy Spe c im en
Th e specimen may behave in a duc tile manner (i.e . 0 perce nt cleavage area ). bUllhe structure could behave in a brittle manner at the same temperature
Temperat ure
How do we overcome this? We 'calibrate' the Charpy on the actual stru cture
,
>ODIi _ .
FRACTURES IN SHIPS (In Fracture Mechanics Notes) •
Ship hulls used to be 'riveted ' tog ether
•
In all pro bability, cracks in stee l hull plates of ships wa s common place. •
Except tha t duo to the riv eted const ruct ion te ch niq ues of the era, a cra ck in a sing le plate was no t catas trophic a nd \\IO uld be att ributed to an occasro nar single bad stee l plate from the stee l m ill or faulty fit -up in manufacture
•
A britt le fracture, would on ly run to the next riv eted j oint. lypica lly not mom than 20 te et in le ngt h, with noti cea ble but not catas troph ic lea kage wIlic h cou ld be conta ined until th e next reasonable sche duled re pair
FRACTURES IN SHIPS (In Fracture Mechan ics Notes) • The 'Liberty' carg o ships we re we lded structures. bui lt in the USA during Wo rld War 2 to bring 'liberty to Europe' • Out of 2700 Lib erty ships built to supply UK, 400 sustained fractures, 90 of which were considered serious and 10 broke completely in two. •
1000 suffered significant failures betw een 1942-1946because of low temperatures. while 200 suffered serious fractures betwee n 1942-1952
• The US Gove rnme nt knew some thing was wrong, because the failure rate of the welded Liberty ships wer e very high in the North At lantic , while literally NO N-EX ISTENT in the warm waters of the South Pacific,
1
THE LIBERTY SHIPS
Sd1enedady, 1943 New shiP FoJ/W ", h4roour. A ". temp. was ~ -Je
Water temp. - 4C tight win d s . Many of the trectvres on the Liberty shIps Imtlared at poor w eld s, nor assoCiated
With d eSi gn de t"il$
The qui ckest a Liberty ship was built 5 days after the keel was laid'
THE LIBERTY SHIPS • The Liberty ships are an example of where the Charpy spe cimen has been calibrated against structural behavi our. • The Liberty Ships were the first ships to have an all welded hull. A large number of the ships failed in a brittle manner. The ship plates were tested using the Charpy specimen to determine: • the plates where brittle fractur e init iated
...........
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?
• the plates where brittle frac ture propagated
• the plates where brittle fractu re arrested 1<: _
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THE LIBERTY SHIPS •
The results were: • init iation (so urce) plates had an ave rage Charpy energy of 7 ft Ibf • propagation plates had an ave rage Cha rpy ene rgy of 10 It Ibf • arrest plates had an average Charpy energy of 16 ft Ibf
•
•
7 ft Ib
t = : I f i ! t i J 1 0 ft ib 16 ft Ib
Therefore , to arrest a fracture, a plate would need to have a Charpy energy greater than 16ft Ibf. Also, design changes were made to remove local stress concentrations (they removed square hatch covers).
(el Penspe, 2006 Re' 6i1
THE TITANIC
- - ,.,- -
T he Roval Mail Ship Titanic: D id ; Mflalluq"ical Failul'<: Came a Night In Remember !
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THE TITANIC •
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_ Comp are the Titanic hull ste er with a mod ern (A3 6) steel. _ It is apparent thai the steel us ed for the hull was not suite d for service at low tem peratures , _ The sea water tempe ratur e at the l ime of the collision was -2" C . :e:"""~~ "" ""
THE TITANIC _ The steel used in constructing the RMS Titanic was probably the best plain ca rbon ship orate available in the period of 1909 10 1911, _ but it would not be acceptable at the presen l li me for any construc tion purposes and part icula rly not for ship construction. _ W hether a ship constructed of modern steel would have suffered as much damage as the Titanic in a similar acci dent seems prob lem atic. _N avigational aides exist no w that did not exist in 1912; hence , iceb ergs would be sighted at a much grea ter distance , allowing more time for evas ive actio n, _ If the Titanic had not collided with the iceber g , it coul d have had a caree r of mor e tha n 20 yea rs as its sister ship, the Olympic , had , _ II was built of simil ar steel, in Ihe same shipyard, and from the same des ign. _ The only differe nce was a big iceberg
1<1 _ _
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2
LINE PIPE CHARPY TOUGHNESS • Many mate rial specifications require a certain toug hness level. • In pipelines, we measure toughness using the 'Charpy' test. • Th e toughness is measured in 'Joules' or It. Ibs.).
THE CHARPY SPECIMEN: 'Subsize' •
Th e full-s ize Cha rpy V -notc h impact test specime n is a spec imen with a length of 55 mm and a square cros s-section with 10 m m sides .
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• A V-notch of 45 degree included angle, 2 mm deep with a 0.25 mm radius of curvature is machi ned in the centre of the length.
•
Reduced secti on (sub- size) tes t specim ens are also defin ed , with a wid th of 6.7 mm (a 'tw o-thirds size ' speci me n) and 5 mm (a 'half size' spe cime n). • The notch is mac hined in one of the narrowe r faces
FULL
213
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6.7mm
5mm
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4. FRACTURE MECHANICS
FRACTURE MECHANICS· Regimes Linear Elastic (@e/weMechamcs In this regime. the crac k driving force is measured by a par ameter
called the stress intensity factor (K,l, is generally a function of the applied stress . the crac k size and the geometry of lhe component Elasf!c·Plas ric Fracture Mechanics The crac k driving force in this reg ime is measured by a pa ramete r cal led the J Integral (J,), or by a displacemen t, CrOD, J, defines the wo rk do ne under the applie d stresses in the vicinity of the crack. GTOD is a measure of the st rain at the crac k tip. Limit Load Ana l ysis For ma teria ls that are highly ducti le , this analy sis me thod assumes that the entire cross section althe component becomes fully plastic be fore the coset of failure
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FRACTURE MECHANICS - Defects lower failure
stress _ In fracture me chani cs we want to predictthe fai lure stress of a defect in a stru cture. So, if we have a crack of length 25mm, in a cylin der, we wantto know at wha t pre ssure the cylinde r will fail.
(
() ()
_ For example if I burst the defect free cylinder I migh t find - - - ~====;:: the failure pressure to be 100bar. (
_ If l tben pressurised the same cylinder with the 25mm crack to fai lure , I might find the cylinder fails at 65bar. -
~
_ Obviously, it wou ld be better if I had a met hOd for ca lculating this failure press ure, rather than testing the cylinders. _ Fracture mechanics gives me th is method .
FRACTURE MECHANICS - Linking to Applied Mechanics _ In app lied mec hani cs, I compare a remotely app lied stress on a defect free structure, to the yield strength of the material of the structure . _ If app lied stress--yie'd strength, I assu me my stru cture is overlo aded, and liable to fail _ In effect we are comparing load (applied stress) with resistance (yield strength).
LOAD -
Ear thquake damage 10 a pipeline
-
RESISTANCE
LOAD
>
RESISTANCE
Failure
LOAD
<
RESISTANCE
No failure
1<, _2005 _ '
2
FRACTURE MECHANICS· Method _ W e have a similar situation with fr acture mechanics - we apply a load to a crac ked structure and want to predict the failure _ The stre ss in the cracked structure is not simply the appl ied stress - the appl ied stress is magnified around the crac k tip. e rbererore . we need a meas ure of the stresses & strains around the crac k tip _ _ Fract ure mecha nics does this in different ways. such as a measure of the ene rgy, or stress intensity, or displacement loca l to the crack li p. There fore , this is my local stress /strain on my cracked struc ture. _ The local resistance against the se energ ies. intensities, displacemen ts is not yield strength bulloughness
LOAD - - -
TOUGHNESS
_ If local stress, ene rgy or dis placement>toug hness , I assume my structu re is ove rloaded , and liable to fail a a eca use I meas ure the intens ity of my stresses and stra ins aroun d my crack tip in different ways , I also meas ure my toughness in d ifferent ways
FRACTURE MECHANICS· Method
Resistance
Driving force LOA D -
-
TOUGHNESS
LOAD
>
TOUGHNESS
Failure
LOAD
<
TOUGHNE SS
No failure
2
FRACTURE MECHANICS - Method Summary _In applied mechanics I need th ree things to dete rmine the effect of loading on my defect -free struct ure: _1. I need a measure of the severity of any load on the structure . I usually measure the severity of the load on my structu re, by con vert ing tho load to a stress or a strain in the structure _e g the app lied stress in a press urised cylinde r is (pressure x cylinder diam eter)/(2x cylinder thickness) _2. I need a meas ure of the resistance to th is load in the struc ture. I usually do this by measuring some material prope rty that is related to resisting the loads. - e.9 the structu re yie ld strength _3. I need an equation thai links this load to this resista nce , and defines a failure _ Failure Stress = Yield stress = (pressu re at failure x cylinder diameter)/(2x cylinder thickness) _ By knowing these three thi ngs, I can ens ure my load in my structu re is always below my calcu lated failure load 53
FRACTURE MECHANICS - Method Summary _In fra cture mechanics I need th ree things to determine the effect of loading on my defective structure: _1 . I need a measu re of the sever ity of any load on t he structure , I us ually measu re the seve rity of the load on my str ucture , by converting the load to a stress or strain 'inte nsity' parameter around the defect. _ e ,g, the applied stress 'intensity' aro und a defect in a pressurised cylinder is a function of pressu re, cy linder and defect d imensions. _2 . I need a measure of the res istance to this load around the defec t. usua lly do this by measuring some material property that is related to resist ing the cracks . _ e,g, the structure resistance to cracks (tough ness) _3. I need an equation tha t lin ks thi s load to this resistance, and de fines a failure failure _ Failure Stress = f(tough ness, defect size and shape and structu re's size and shape) _ By knowing the se three things, I ca n ens ure my load in my structu re is always below my calculated failure load .
2
FRACTURE MECHANICS - Method •
Fracture mechanics is the application of applied mechanics to the problem of predicting the extension behaviour of a pre-existing crack .
•
Since fracture consists of stable or unstable progressive growth of a crack, it is only the material which is immediately adjacent to the crack tip which is actually breaking at any particular instant. • ccnseoce nuy fracture mechanics focuses exclus ively on circumstances existing et the crack tip where the discrete volume of materia l there is considered 10 break when some cr itical condition is reached • The stresses and strains present in that localised volume of material ca n on ly be Iransmill ed 10 it from the surround ing material. • So by using the equilibrium and compa tibility cond itions 01 elastic ity and plasticity, fractu re mechanics seeks to define the local condit ions under which the crack will exte nd but by using globa l parameters such as load and geometry
55
FRACTURE MECHANICS· Method _ In applied mechanics we can cons ider the loading on a structure in two ways : _ Stress _ Strain _ Stress and strain are linked, but we have a choice of assessing the loads on a structure using either stress or strain _ In fracture mechanics we have a similar situation, We can consider the loads around a crack in a variety of ways: _ Stresses at the crack tip _ Strains at the crac k tip _ Energy in the cracked body _ Again all these three parameters are linked toge ther - as we will find out later. _ We will look at modelling the behaviour of a crack ed structure using the stresses and strains around a crack (the 'load' ), and as a measure of its toughness rreststance').
21
o
FRACTURE MECHANICS - Prior to -1950
•
r
Early fract ure mechanics wor k w as done on brittle mater ials _ Inglis 1913 • Griffiths 1921
solution for elastic stresses at a crack t ip • The Inglis • Although primarily an analysis of stresses local to an elliptical hole in a flat plate, this early analysis also cont ributed the case whe re the ellipse is collapsed to a crac k and showed that the stre sse s, am ' at the tip of what is no w considered a cra gk were singular in nature and given by:
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• p
j,
the ' ad i" , " f ( u<';ature"' [he "I'
I
I
I
I
"
r' l P.""",, ,,005 ~ . " ..1
5'
I FRACTURE MECHANICS - Prior to -1950 •
(J
The Inglis equation predi cts an infinite stress at the crack tip as p---tO and so a material contai ning a sharp crac k should in principl e fail at an infinitesimal load. This result caused concern and indeed was the mo tivation for Griffith to later devel op his fracture theory based on an energy consideration rather than one of local stress.
• The Griffith energy balance • Griffith used this concept the first law of thermodynamics (theorem of minim um potential ene rg y) to reso lve Inglis' infinite str ess para dox [Griffith, 1921]_ A crack will extend only if the total energ y of the system reduces or rem ains cons tant as a result. The critical con dition s for fracture are thus where crac k extension occu rs under equilibri um condition s, i.e . with no change in total energy.
2
FRACTURE MECHANICS - Prior to -1950
• Using the stress analysis for an elliptical hole in a flat plate of Inglis Griffith obtained for a centre crack ed panel : ,,-f>c-,...
' E' \ " a j = -- 1, ( na- J
IT" ,he n:m...... ~ ',," "'lOll 'trC" I: ",ho: da,u.e m, ,,~ulu, "f ,f><- ,,,•.,..,,..1 r.«
,he ,,,rlx,,"
• Irwin later modified this to account for some plasticity. Before proposin g an essentially similar approach but which was more convenient for solving engine ering problems. , " _ lfa C, - - -
E
I':nc, i':Y rcle", c rale
:{ )f"
wick p h ,,· ill r h n..
,,,,.,, w i,l, ,, cr a,' k " j k ngth !"
FRACTURE MECHANICS - Status in 1950
.Prior to 1950, it was not customary for a fracture fa ilure repo rt to mention the presence of cracks - Cracks were considered unacceptable in terms of quality, and there seemed to be a reluctance to adm it to their presence. • Plus, it was not poss ible to readily apply the early fracture mechanics work as it was only applicable to 'perfectly elastic' materials (e.g. brittle materials such as glass ) where plastic strains were not present; therefore, it was not directly applicable to engineering mate rials. • In the 19505 there was interest in fracture in the aircraft industry in the USA, particularly in alum inium, but also in the plast ics used in the industry. iOl
p..-..:- 100& ........"
eo
3'
THE STRESS INTENSITY FACTOR APPROACH TO FRACTURE
• • • • •
•
r
10
Expe rimental work by Kies , and theoretical work by Irwin found that the stress fields around a crack tip could be rep resented by their 'intensity', K ('K ' afte r Kies ). And the ma ximum 'K' a material could withstand - Kc - was its toughness He called this a 'K field' K is a function of applied stress, and the size and position of crac k At fa ilu re: (Jc=.1JK c2j r::af_5
y We now have: • A crack driving force, K • A tough ness (resistance) measure from tests, x, • And a methodology that linked stress, def ect size and toughness . Thi s was the start of applied fractur e mechani cs
0
YJo-
K
0.
= ~ (a fun~LI"R, rtil
/
~ 2Jr
'" , Distanc e from crack tip
( o: ",, _ ;'OC<; ~· ,
"
10
THE STRESS INTENSITY FACTOR· K
r
•
The K field is the asymp totic crack tip field in an elast ic solid . The K field char acteri ses the fracture proce ss provided that the process occurs in an elastic field .
• • •
The stre sses and strains tend to infinity at the crack tip (the stress fie ld is singu lar , ie. there is a sing ularity at the crack tip).
•
The stresses and strai ns at any position around the crack tip follow the stress intens ity facto r, K, fo r sma ll scale yielding . It is related to the di rection of the stresses in the x.y and Z directions X K1 is the stress intensity factor for Mode I loading , I.e . tensile loading (this mode openstoe crack surfaces) . The singular ity is _'_
~ ->. ~
"
JY
•
~
.,
lei _ _ _ 2C06_to •
J; (1
K (a function of II) ., = J,sm:
(J)~
'"
/
'.
";"101_""".,(0)
.-:.
yield strength
r Distance from crack lip
sa
3
THE STRESS INTENSITY FACTOR - Differing Ks _ We can have three different type s of K, depend ing on the di splacement of the crack surfaces: - K 1 = opening or tensile mode (this is
I:::/:
(,~ . .
v/ 'IV
the most common in engineering rr -- - -_ - K 2 = sliding or in plan e shear m ode - - - -
./>1
- K3 = tearing or antipfane mOd ~
»> / ~~ /
_ Our structure fail s when the appli ed K reaches the fr actur e toughness of the material, 1<.:. Kc is measu red on a bend speci men of thickness B: Kc=FcS/BW05.f(aNol)
F
I 1'"
Z//
I... ~
C'
~
J
FI2
s
Il
displacement
a F 63
THE STRESS INTENSITY FACTOR· Stresses
I
I
0
Ie!
Mode I Load ing y
~' r
0"
IJ
2a
O(
A.' ,
O( _o _ .vn
&.
"
.J. " • .....- ..... _
... . . ..- .
x 30)
At
(I _ (T ,, = , - C(l~ -:; l - ~ i n -; s l n ,
.1. "~~b-__'"
" " " " " _ . ...bI ..._
" ~ -&..1 froT~ -...
([".,..o, •• ,.•• <'9- ......."
A",
-
-
l -s m ~sm-
.._ ._, ) a , 0 30
= ,\ /-, • .':J - ~·t",-;sm _ :;_ cos , _
.........
,p . . . e...... -..-..: .. , . . ,....... ....,.., ,...,....,. ....... ~ •• 'fOr>:> ..... --.pl
C - , ... l . _ E.5h< .·oa.... L...... .-.a LE....: .......... __ ~_"II .. __...._ •• _
•• , .,..""
......,.... ' ...' _. .£F ... ~" .... ,.. _")'~"'--.""',.......... _.~""
Icl ..... _l'IlO6 ...... '"
"
3
THE STRESS INTENSITY FACTOREquation
I
10
r:
1 •
K = Yn (r:a )O.5
•
Failure occu rs when K= Kc
•
The str ess at failu re is: • c, = KJY (r:a c )O.5 • This gives the critical crack (or ma ximum tolerable crac k) size, ae
2h
2b
j
j
r
THE STRESS INTENSITY FACTOREquation
I
cr
1
•
The K field is a function of the defect size/s hape, and the stru ctu res size/sha pe
•
If I have a cent re cracked panel, of width 2b and length 2h, my stress intensity facto r is: K = Y(T( na )0.5
• •
2h 2a
• • •
2b
j
(J
j
alb
hlb
0 03
inf.
04 05
Y 1 1.5 3
• 07 So, as I increase paramete rs, my K varies It will reach a value that I cannot exceed - the tou gh ness
66
3
THE STRESS INTENSITY FACTORCritical (Toughness) Values K, (MN / m J/ 2)
100-350 170 140 42 -60 6-20 3 0.02 0.2
Cu , Ni,AI PV Steel Mild Steel Fibre Glass Cast Iron Granite Cement Ice
STRESS INTENSITY FACTOR - Example o~
1
I
•
An aircraft wing is made from an aluminium alloy which has a yield stress of 200 MPa, and a measu red toughn ess (Kel of 120 MPam o s
•
It contains an edge crack, and we can ass ume a Y valu e of 1.12 for this crack.
•
The aircraft designer requires a safely facto r of 2 on his/her desi gn stress, which is equal 10yie ld strength . I.e. 100MPa.
• • •
What is the maximum crack size (a c ) we can tolerate?
Edgti crack
.>: a,
j <:.........-:IOOli R..... '
cr"~
I
I~
r:
K c ;: YO nom(rt 8 c )O,5
a c =(1 1 r: ) (KjYa norn)2
• Thi s give s the critical cra ck (or maximum tolerable crac k) size, a, of a.37m se
3
5. THE PLASTIC ZONE AROUND A CRACK TIP
69
LEFM*? .By 1975, LE FM was fully codified in the standard ASME SECTION XI (used extensively on nuclear pressure vessels)
_This aimed to meet requirements of ASME Section Ill , App G (used exten sively on pressure vessels) .App G of ASME III was to protect against what they called 'nonductile failure' _ It was aimed at heavy section welded pressure vessels: _OK for thick structures and brittle materials. _ In a metal , there is no such thing as plasti city free failure. _LEFM is therefore only a mechanical concept, and bears no relat ionship to the failure m echanism _Crack tip plasticity sets the criterio n for cracking, not remo te plastici ty.
OJOl."om ,,, "",.
3
THE WAR AGAINST PLASTICITY " e ~.
" ",,<:,t; >D'~M> TIi ",,' tR,A"' .''' r' U lo"r
. :.-1::_
" H'Q-I I:rRE ,....-nJ
._C OO Jrr'l l"
'>;,:C Oi L " _
" " TE.. ,u ' 00
.. ~ Tf "' All,.. .... .,lfi SI .. t " .....
......-s l/C' ....
.... ~N '-
' tl'ti","
.,T>< ,,,,,,,,,,,,,..
_ rr,<,N..
..-V_' .:..y
,:>;.. ...,1; ! r ......'.
lEF",
;;'.." :;rrLC
f'uo H ,C
THE ROLE OF PLASTICITY . "-I(.J y c:-.
Fa ilure Stress 0,
---
,, ,,
Plast ic conepee ------~--------------, (limilIOa d)
increas ing toughness
,
,, ,
,,
,,
,,
,
'''' ~
...
----LE-FM
_ As we load up a cradled strvctu'e, a 101 01 the energy ,s absorbed 0, Defect size , a plashc deform ation (ll'()l,or'l(l the crack t,p. _ This allows me stresses to "rela ' and " prevents stres ses (JOInQ atlOve the l" e1d sl'el'lglh . _ 1\ also enSU'e$Il\at" 1have exte ns ive p1aslocrty. the la~ure Dad 0' the crack ed structu'e wiI correspond to ceastc collapse" (Of ~ readles a limit Joad"). I e the structure wiI fa,1 by O'o'erload on its remaooll lig.ament and the e'l'ed aI!he CllId< IS 10 SImply ,educe ee Ctl)§ sectIOnal area 01 the SlructlJl e _ Note !l'os IS a SImple VIeW ai-plastIC coIapse- - _ 1 tall< about me later _ Thrs IS good news for lI1e slruclure - plaslOClly allows hogne< lallu re loads _ BuI ll is bad news lor linear elaslic fracture me<:M.anlCs. as LE FM rebes on the stress Slngulat1ly' • stresses 90"'9 to ...tlnily al the crad< IIp . He nce . p1as~cfly ;nvil kda:es my l EFM models
:c1_.......,.,.R..,;;'
n
3
6. CRACK TIP OPENING DISPLACEMENT AND J
THE ROLE OF PLASTICITY & CRACK OPEN ING
-
r
. ",I1Om
E ~ E, plane stress , or
E = EI( I -1"), pla"e strain
_l I the material's fracture toughnes s [m terms of crack tip opening cis ntaco mcnt). is 1\ ' fa ilure occu rs ",'hen (, > (\ (e) Peo,p." 2000 R., 5i1
3
CTOD _ Crack opening displacement is simi lar to stress intensity in that it is a function of crac k length a and load ( e.q. remole stress , (l ) _ The advantages of ClOD as a crack char acterising par ameter is its applicability over the whole range of loading , from linear elasti c fracture to plast ic collapse. _ Cl OD can be used in the same way as stress intensity:
. you can obtain configuration factors ('y') for non -infinite shapes _ A critical maximum ClOD ( t\
) is a material property. and
so on .
(f
CTOD
_ W e ca n easily visualise ClOD by considering the specimen we use to measure o, _T h e specimen is thickn ess B
~
~ F/2
F/2
C ll
~ /w
+v;
Displace ment.V
F
• .sc=[1\2( 1 .\,2)/2cr~E I +[O.4(W ·a )VJ f[04W +O.6a+ z ) etastc opening {CIP ._2OO!i_~ '
where
Kc=FcS/BWoS.f(alW )
plastic o pen ing
te
FRACTURE MECHANICS - STATUS IN THE 19605 and emergence of 'J' and 'CTOD' _ The early work of Kies and Irwin was used in the aircraft industry. • In the 1960s there was a grea t interest growing in the safety of nuclear power plants. _These plants used pressure vessel grade steels of very high toughness, and the existing LEFM was not applicable to these steels. • In the late 60s , Jim Rice developed a theory ('J ') that allo wed the crack driv ing force to be quantified in a material exh ibiting ductility (e.g. a pressure vessel steel) _J is a measure of the 'energy release rate ' as the crack dri ves forward, and is resisted by the material ahead of the crack . J characterises the stress-stra in field around the crack .
FRACTURE MECHANICS - STATUS IN THE 19605 and e m e rg e nc e of 'J' and 'CTOD' (cont.) .At the same time researchers in the UK developed the 'crack tip opening displacement (CTOD)' to measure the toughness of a material, merely by measuring the disp lacement at the c rack tip .In the early 70s, researchers Begley and Landes were able to characterise J as a fracture toughness, Jet I.e. the material's resis tance to the crack dr iving force . • The relationsh ip linking toughness (J), flaw size and stressing to elastic plastic materials was later (1976) established. A t the same time , the UK established th is link ing for CTOD. _Hence, in the early 70s we now had fracture mechanics approaches that was applicab le to tough materials .
78
3
THE J INTEGRAL AND CTOD •
•
Bot h J and 0 (GTOD) are valid frac ture toughness parame ters for an elas tic-plast ic solid. J and 6 are relat ed ,} = ma , ('i •
m is a h mctlo n of the strain harden ing cha racte ristics o f the materia l and the con stra.n t (i.e. the geo mel ry a nd the stress sta:e). II vali es between 1 and 2
KI· _ J _ .. -. -ma , d
•
For elastic behav iour :
•
• E' " E lor plane stret~, and E' = EIl for plain strain I can measure J and CTOD on a bend spec imen of thickness B:
v'
F~
\..~J1 • •
Jc= [K/ (1 -\, 7)/2[T~E l
~ '----
Vp
Drsptacement. q or V
+ 2UJB(W-a)
;\=[ K,,2(1-v 2) /2o yE] +[04(W-a)V p]/ [O .4W+O.6a+z) elastic J,6
F
oeste J,ii
where Kc=F , S! B WJ ~.f( a i\N )
CONDITIONS FOR FAILURE • •
• •
A crack ed structu re will fail if the app lied K or ClOD or J reaches a critica l level. This level is called the ma teri al' s fractu re toug hness Frac ture toughness is a measure of the abi lity of a material to con tai n a crack the higher the toughness , the mo re res istant is the mate rial to the presence of a defect. The f ract ure toug hness can be measured in terms of K, CTOD , G or J. In ter ms of K:
Kr
No failure Fa ilure
The fracture toughness of a ma terial is dependent on many things including : temperature , sect ion thick ness , orienta tion, etc .. If we have brittle materia l, we can use any of the above approaches and measu res of toughness to de term ine if our structure will fail. If our ma terial is not brittle (and mos t modern structu ral mate rials are not ), we use CTOD or J.
88
4(
7. FRACTURE TOUGHNESS TESTING •
Frac ture toughness is a measure of the resistance of a materi al to fracture when a crack is present.
•
Fracture toughness is measured using standard fractu re toug hness test specimens (e.g. sing le edge notch bend specimen or compact tension specimen).
•
There are a number of standards that specify the proc edures for fracture toughness testing . including Ame rica n Socie ty for Testing and Materials (ASTM), the British Standards Institute (8 SI), the International Institute of Standards (ISO) and the Japan Socie ty of Mec hanical Engineer s (JSME),
•
Existing fracture toug hne ss standards include proc edures fo r KIC• K-R curves , J ~.
J-R curves, Cl OD and K ia tes ting.
7. FRACTURE TOUGHNESS TESTING
82
4
CTOD Testing
• CTOD testing • Weld metal and HAZ (detailed HAZ study ) tested at _10°C
...
........" "",,"" ,., M..., ~ .
-
"-
I.
J
B3
CTOD Metallography
• erao metallography, clea vage initiation sites
·", _2CU_ ~ 1
4:
CTOD Equations
w
r:
~ l -,,-))] 2 IS . -3. [1.9 9--"-(I--"-X 9 _ ' -"-)+ 2 W 'l lr 21 + 2 " X I _a )1 <
/ -"-' = -l il') (
3
5
w'w
IV
/I'
IJ'
If
es
l<:_~"""
CTOD Equations. example _Example of ClOD calculation from a material test eThe 3-point bend test (SENB3) showed some plasticity in the loaddisplacement da ta but finally failed by fast frac ture _Material da ta: E = 207000 Nm m-2 , v = 0 .3 e'rest and spec im en data: _ V p = 1.15mm
• p = 22.6KN •
Ciy
= 450Nmm -2
• Span, S, = 4W • Dimensions, B = W = 25mm , a = 12.5mm
. rp = O.4 (<)_2006 _ ,
86
CTOD Equations - example (cont) • Calculation of K
/ .:!...) computes 10 10.65 for ~ = 12.5 = 0 .5 and S = 4W = l OOmm
lw
K
,
~
W
p
/
RJW'
25
,,-) ~ 22.6'-"3/ "-)~ (1 80 . 8 XI O . 65 ) ~ 1 92 5 . 2 xmm-"
lw
25m'
lw
• Elastic compone nl of eraD J = •
K/(l- Il) = (1925,2)"(1- 0.3') = 0,0 IS lmm 2~ ,E
(2X450X207000)
• Plastic component of eraD j
-
c ,, -
r
P
(w -il)VI'
. ) r, (W-a +u
(115X04X125) (04X'2.') +125
Total CTOD
0.329111111
0= be + op= O.347mm Dominated by plastic com ponent
CTOD Specimens and 'constraint' Full
Scale W id e
plate
~
SENB !
t
Or interna l pressure
Low er Bo und (Conservative)
Constraint
f i g LJ r ~ t mm
Pmf R De nys
8. PLASTIC COLLAPSE
89
PLASTIC COLLAPSE _My material may be so tough, that the corecr will no! fracture my structu re _ Thonk of copper or alumini um that are not usually affected by notches/defects _ If my material deforms. it fails by co llapse ot the l.qament below the defe ct _ This lig ament goes fully plastic, and failure i$ by overlodd , e.q. the Sl ,t:SS reaches UTS
This is known as plastic colla pse , a nd
is usually govern ed by the mate rial's
Stress
----
DEFORMATION
fail if my material can deform fr:~~i~ it. Will.collapse
stre ngth propert ies
NOT toughness 90
4:
PLASTIC COLLAPSE _ Our defect in our pipel ine can 'collapse' in various ways. _ For example. a part wall defect in a pipeline can fail through the wall, and lea k, but it will not cause the pipeline to rupture . The pipe is leaking. but it is not destroyed I _ This is a 'local' coll apse rather than a 'global' collapse
a c onso er a plate containing a defe ct - it can 'co llapse' in various ways
I
I
B,
B,
~
~
Loca l Collapse
Net Section Yield ing Collapse
m I
t
~ Gross Section Yield ing Collapse
('1_ 2OVtI ~ _· ,
at
PLASTIC COLLAPSE IN PIPELINES
Local (Yielding of remaining ligament
Global , NSY (Net Section Yielding)
Global, GSY (Gross Section Yielding) 92
PLASTIC COLLAPSE EXAMPLE· PART WALL DEFECT IN PIPELINE d I
where 0
-
a
0
d
0
t A
0 0
A, M
20
d I 1- - 1M
a u,
,,'
I- -
(Y ,
0
-----
failure stress flow stress (-(cry + 0UTs)/2) defect depth pipe wailihickness cross sectional area of meta l loss original cross sectional area Folias factor (bulging factor)
-
_. J
_
r
,------;--~
XI
=
I + O ,40( ~
9. FRACTURE MECHANICS METHODOLOGIES
(e: Po,,,,,,, l000Rev(i; '
4-
FRACTURE MECHANICS· BSI BS 7910 & API 579 • •
•
•
• •
•
The British Standa rds Insti tute have produced a complete fract ure and fat igue assessment document - SSt BS 79 10 (formerly PO 6493). It presents procedures for conducting an 'engineeri ng critical assessment', whereby you can assess defects in structures using 'fitness for purpose' (fracture mechanics ) me thods . 857910 presents procedu res for fract ure , collapse and fatigu e me thods, but it focuses on fracture and fatigue . A variety of fracture approaches can be used (Cl OD. K, J). This document is highly recommended for use on any structu re . However, it is rare ly used on pipelines (other than girth welds and fitt ings ) because our pipeline stee l is ducti le, and t herefore we are mor e interested in ductile failure . The pipeline indust ry has develo ped its own methods over the past 40 yea rs. and these are internationally accepted Therefore, use BSI BS 7910 - it is a good document - but we hav e 'bette r' me thods for pipelines , that will g ive us more accu rate pred ictions. BS 7910 recommends the use 01 the pipeline methods , API 579 has bee n published, giving ge neral Ifp met hods for process plant.
FRACTURE MECHANICS BSI BS 7910 & API 579 • •
•
•
• •
•
The British Standards Institute have produced a compl ete fracture and fatig ue assessment document - BSI BS 7910 (formerly PD 6493). It prese nts procedures for conducting an 'engineering crit ica l assessment", whereby you can assess defects in structures using 'fitness for purpose' (frac ture mec hanics) metho ds. BS79 10 presents proc edu res for fracture , collapse and fatigue methods , but it foc uses on fractu re and fat igue , A variety of frac ture approaches ca n be used (CTOD, K, J). This docume nt is high ly recommended for usc on any structure. However, it is ra rely used on pipelines (other than girth welds and fittings) because our pipeline steel is ductil e, and therefore we are more interest ed in ductile fa ilure. The pipeline indus try has develo ped its own methods over the past 40 yea rs, and these are internationally accep ted , Therefore , use BSI BS 79 10· it is a good document ~ but we have 'better' methods lor pipelines, that will give us more accu rate predictions . BS 7910 recommends the use of the pipe line me thods. A PI 579 has been pub lished . giving general ffp method s for process plant
4:
FRACTURE MECHANICS BSI BS 7910 & API 579
•
These docum ents attempt to describe a failure by both fractu re and E"" '9' ~bM'OOo collapse.
•
This is reasonable: DUC T ILE
• If my material is d uct ile, il will collapse • If it is brittle, it w ill fracture.
•
But, I must also be able to describe a failu re in the transition region of my ductile brittle behaviour in some steels.
•
This is done by my failure assessment diag ram. ' FA D'
•
I can desc ribe all my failure s in one diagram
TRA NS ' "
,
BRITTL E
i, :\
Temperature
~ .
ISA FE I
."
m
0 (e)
)~AL
'I' "
t"'d 10.J ,1.,,,,.,:
,
u ,"
PO" _ ' 20C6R0>6i l
97
FAILURE ASSESSMENT DIAGRAMS
• • •
My material can fail by brittle fracture, but in mo st structural materials, plasticity effects precede failure, and, in the lim it, gross yielding effects predom inate and failure occurs by plastic colla pse. Therefore the FAD accounts for the range of possible behaviours , i.e . elastic fracture , plasticity effects through to plastic collapse. In this diagram , the proximit y to fracture is given on the vertical axis as the ratio of applied stress intensity. K" to fractu re toughn ess , K",,,:
•
K, " KiKmo;
If K, :: 1, failure is predicted to occu r by brittle fracture, The proximit y to plastic collapse is given by the ratio of applied net section stress. 0 0 ' to now stress 0 ,( flow stress is a stress between yield and UTS) •
•
'-
.r:. .
".-- - - - - - - , 1.D
i
~mpn l l i " p
"I
• S,=" /'" •
i e. if S, = 1, failure is predicted to occur by plastic collapse.
"'
""'-''"''- '"'',S,"".o-"""",<,'."'~" 98
4
FAILURE ASSESSMENT DIAGRAMS •
•
A failu re locus provides the con nection between Kr and
s-
•
Any asses sment poin t falling 00 or below the fa ilure locus means that the flaw is stable and is not a significa nt ris k of fa
•
A ssessment poin ts above the failure locus represent unacceptable flaws wh ich may ca use failure.
(el
~
I"o'$"'s",",' lin..
8.8-
/
] .
f
Fo r materials which fracture in an elastic-plastic o.&fashion, alternative £ f fracture toughne ss parameters have been proposed : u . J, and the crack l ip openin g displacement c'ron. u •
•
"I ,.o,'-J
Cl OD testing and as sessment p rocedure s are popu lar in the pipeline industry
"'
Wh en the se parameters describe fracture, KI and Klc are replaced by J or CrOD using suitable relat ions. However, the principle of the assessment procedure remains the same.
O,t
0,6 5,
09
1.0
1.7
P OffiPO" 200fi ..... ~,'
FRACTURE MECHANICS· Perspective •
•
•
•
•
Fra cture me chan ic s provides us with the sc ien c e an d models 10 understand the behaviour o f defe ct s in st ruct ure s It is used extensiv ely around the world , and in most industries It form s the basis of all the methods we use in pipelines Howeve r, we hav e developed our own methods over the years. wh ich have ta ken the com ple~lty Ol.t of the caicclancns . Bul lhey are st~1 based on fract ure mecha nics
1 Fracture Mechan ics
Science
I
in Pipelines Codes
IBSI 79 10 II A PI 579 I I II I as F1 0~
Specifi c Guidelines
IASME B3; ~ 1 [ CSAZ164 I p NV RP F1011
General Codification
BeSf Pract ices: Corrosion
Gouges
API 1104
AS ME 631
pNV
IASME B31(31
I
Ballelle
,
G!lfh W91ds
Crack Prop
'00
How to Assess Fatigue
Penspen Integrity
1
INTRODUCTION
,
INTROOUCTION - Structures can be Subjected to Static and Cyclic Stresses Stress Stress Static Stress
Cyclic Stress
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INTRODUCTION· Many Structures Are Subjected To Varying Stress Stress
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INTRODUCTION - Metal Fatigue • As iron and steel structures came into wide spread use , engineers were faced with failures occurring well below the tensile strength of the materials. • The materials were duc tile , but the failu res exh ibited little or no ductility. • A tensile lest on m ild steel would be expected to sho w 20% elongation
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_ but these failures exhibi ted no visible signs of deformation .
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• However, these struct ures ha d been subjected 10 repeated stressing
(cyclic stresses). Hence , engi neers were introduced to 'fatigue'.
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• 'Met al fatigue ' was reported by railroad engineers in the 18805 .
• A numb er of accidents involvin g failed train axles led engineers 10 describ e the parts as being "tired :' or "fatigued ."
,
INTRODUCTION - Early Metal Fatigue Studies •
Testi ng to e valuate the fatigue resistance of metals started in Germany as early as 1829. • Most of the ea rly failures de....eloped in machine part s wh ich were su bjected to high freq uency repeated loading.
•
How ever, it wa s identified that other, larger structures could fail due to fatigu e • e. g. Sir William Fairburn studi ed th e fatigue design of wrou ght iron bridges in 1860.
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Fatigue failures hav e two areas: • the prog ressi ve de velopmen t of the fatigue crac k, followe d by • fai lure when the applied stresses cause structu ral overload .
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INTRODUCTION - Why would pipelines 'fatigue'? _ The press ure in a pipeline is not con stant. For example :
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e.q. a pipeline carries various prod ucts {batches) will have varyi ng pressures at varying t imes.
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($) "")S¥§E) _ It can vary due to demand , e.q . a pipeline that is supplying a region that uses the energy during the day (lowering the pipeftnes press ure ). but not using it at night (allowing the pipeline's pressure to increase)
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INTRODUCTION - Why would pipelines 'fatigue'? (cont.) _ W hen we lay pipe lines offshore. we can have severe loadings due to waves _These waves move the lay vessel and impose stresses on the pipeline as it is lowered onto the sea bed a 'tensiooers on the lay vessel withstand the high loads. but the pipeline can be high ly stressed . and these stresses vary wit h wave heig ht. movem ent of vessel, etc .
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a consequenuy the girth welds can be under high cyclic stresses _ There are many other causes of pipeline ratig ue (see later notes)
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INTRODUCTION - Effect of Fatigue on Metals . Fatigue loading on a structure can do two th ings: _ It can create cracks that grow 10 fai lure _ It can ass ist existing cracks 10 grow to failure. e w here we have no crac ks present , or ve ry small defects in the structu re, we use t he ' S oN' app roach to asses fatig ue. e w hen we have a crack in the structure, we use fracture mechanics to assess fatigue
INTRODUCTION - Structures Can Contain Cracks
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T he wo rld's first large iron structure was the Iron Bridge . near Telford ill Sh ropsh ire. Bu ilt in 177 9. Note arch to give stiffness Hnd strength , and note cracks in joints.
INTRODUCTION - Pipelines Can Contain Defects
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INTRODUCTION - Effect of Fatigue on Pipel ines •
Extract s from 'W estern European Cross-Coun try Oi l Pipe lines an-year Performance Statistics', CONCAWE. Brussels. Februa ry 2002 (WNW concawe.be): • Ve ry few ( if any ) pipeli nes are be liev ed 10 suffer from deteriorati on due to throughput rela ted effects, for example, metal fatigue • Fatigue failures do sometimes occ ur when pipelines have suffered some construction fault or subsequent oamaq e such as dents.
• The se are relat ive ly infrequ ent causes of sp illag e.
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INTROOUCTION - Case Study on pipeline fatigue fail ure _ 1970 USA gasoJene pipelin e.
_28",0 .281".705psi operating pressu re _Failed in 2000. • $18million clean up/damage bill _ The NTSB concl uded the probable cause of the pipeline failure was: ecorrosion-cw cycl e fatigue cracking that initiated at the edge of the longitudinal seam weld at a pre-existing weld defect
ASSESSMENT OF FATIGUE - 'S-N'
•
7
INTRODUCTION - Case Study on pipeline fatigue f a ilure _ 1970 USA gasolene pipe line.
_28 ",0.281".705psi ope rating pressure _Failed in 2000. _ $18mi llio n clean up/damage bill _The NTSB concluded the probable cause of the pipe line failure was : ecorrosion-ow cyc le fatig ue cracking that initiated at the edge of
the longitudinal seam weld at a pre-existing weld defect
ASSESSMENT OF FATIGUE - 'S·N'
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7
FATIGUE ASSESSMENT - The SoN Curve •
Fatigue is made up of three stag es : initiat ion, propa gation, failure
•
Al l these stages are described by a cyclic stress (8) versus num be r of cycles (N) 10 failure , givi ng an 'S-N· curve
•
The S- N cu rve use s log a rith mic axes
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The 'm ean' S-N cu rve
represents a 50/SO chance of failure ,
and a component des igned on the basis of a mean curve has an equal
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chance of failure or survival.
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FATIGUE ASSESSMENT - The SoN Curve •
The S-N curve is based on
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FATIGUE ASSESSMENT - SoN Curve's Endurance Limi t
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fatigue'.
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• At 1000 cyc les, the fatigue strength is typically a.BUTS Steels show a 'knee' in their S· N curve , This is called the endurance limit or fatigue limit. The S-N curves for non -ferrous or alloy ed materials do not have this knee.
•
Fatigue fai lures in the range 0 ,5 cycles to 1000 cycles are cal led 'low cycle 'H igh cycle fatigue ' is for greater tha n 1000 cycles.
The endu rance lim it of ferrous steels with a UTS less than 1400 Nmrrr s is betwe en 35 and 60% UTS. A good 'rule of thumb' is the lesser of : • 50% UTS or • 700 Nmm? at 1,000,000 cycles,
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FATIGUE ASSESSMENT - The Effect Of Discontinuities on S-N Curves •
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Metal fatigue is the process by which: • a crack can form and grow under repeated or fluctuating loading, or • an existing crack can grow under repeated loading. All structures contain 'st ress concentrations': • notch, surface roughness, a hole, etc., i.e. anything that causes a discontinuityin the structure. • The stresses around these discontinuities are highly concentrated, and are very high adjacent to the discontinuity.
•
Un der static loading, the stress concentration in a ductile m aterial will have no effect, because the amount of highly str essed material is low compared to the material at nominal stress (the m ateria l is constrained by the surrounding elastic m ate rial).
•
In plain material, most of the fatigue life is take n up in initiating the defect. In a structure containing a de fect or stress concentration, most of the fatigu e life is taken up in propagating the defect.
9
FATIGUE ASSESSMENT - The Effect Of Stress Concen trations on SoN Curves •
In ma l erial containing no maio" de fects, fatigue life reduction
is caused either by surface roughness, ()( stress
concentrations. •
We know that an y stre ss concentration Of 'discontinui ty' ca n reduce fatigue lives .
•
All structures contain 'stress ccocenn enoos': • notch , surface roughness. a hole, etc.. l.e. anything that causes a discontinuity in the structure. • The stresses around these discon tinu ities are high ly concentrated , and are very high
adjacent to the discontinuity. •
Fatigue Ufe at a Stress Range of 180 N/mm 2
STRUC TU R E
Unde r static loading. the stress
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FATIGUE ASSESSMENT - The Effect Of Welds on SoN Curves • We lds in structures reduce fatigue lives. • In welded structures we nave two obvious sources of stress concentrations:
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• the weld shape, and defects in the weld, particularly at the surface. • In welded structures the fatigue life is dominated by defect growth, not initiation . • Welded joi nts can contain high residual stresses (that ensure that all cyclic stresses are tensile), large stress concentrations, and crack-see Fatigue life at a defects, resulting in STRUCTURE a major reduction in Stress Range of 2 180 Nlmm fatigue life. Plain Plate Prate with 3 mm diameter hole Prate with fillet welds Plale with 2 mm dee V notch
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10
FATIGUE ASSESSMENT - The Effect Of Welds on SoN Curves •
The fatigue life of a weld is affected by: • stress range. • the type and shape of the weld . a The type of weld "";11dictate the chance of defects being present. and the shape wilt dictate the size of stress concentration, and also affect how easily the joint is inspected .
•
• the presence of defects (over and above those inhe rent in the weld's workmanship limits) • misalignment and other local stress concentrations • size : fatigue life decreases with specimen size. This is well known in machine components (in bending, you have a higher stress gradient in a thin plate , giving rise to a highe r fatigue life than in a thicker plate) . In welded joints , this is due to weld joint dimensions increasing stress concentrations Th e fatigue life of welded joints is not greatly affected by: • yield strength • mean stress or post weld heat treatment (when the loading is fully tens ile)
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FATIGUE ASSESSMENT - Which SoN Curve do we
use? • •
W e use our S·N curves when we have a weld that is free from 'significant' defects. Thi s is difficult to define. • • The tests that the S-N curves are base d on will have used specimens welded using standard proced ures, hence they will conta in typical workmanship defects. • Fo r exa mple, fillet welded join ts will have slag intrusions of depth 0. 15-0 .4 mm at the weld toes. These cannot easily be detected by conventional NDE. • However, the test welds should not contai n significant (e.g. cracks) defects, that can be readily detected .
• •
The 5-N curve we choose must be applica ble to our ma terial, detai l and envi ronment. The 5- N curve we use mus t allow for scatter in data. •
•
An S-N curve two standard deviations (SO) below a mean curve (assuming a log-normal distribution) is the lower 95.4% confidence limit, and represents approximately 2.3% probability of failure , or 97 .7% survival probability. 3 SOs below mean wou ld give us about 99 .8% probability of survival
We usually use the 'mean - 25D' curv e in des ign.
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FATIGUE ASSESSMENT - Different Codes, Different SoN Curves
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FATIGUE ASSESSMENT - Choosing the Correct SN Curve •
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The S-N curve we choose must be applicable to our material, detail and environment It is norma l to use the 'mean - 250' curve in design ... W e must be ca reful when we select an S-N curve: • Different codes have different S-N curves. • Some codes use plai n materia! tests as a basis for their S· N curve , while others use welded specim ens . • Some code $oN curves do not specify the conservatism in the curve or any added safety factors.
• •
•
If you do not know the origin. basis , applicabi lity and built-in safety ma rgins in an S-N curve ... don't use it! The most widely used and accepted weld S-N curves were proposed by The Welding Institute (in the UK ). These have been widely accepted in many structures (bridges, offshore structures, pressure vessels, etc.). Therefore, you can use these curves, or develop your own SAN curve by testing your weld design . • For large we lded structures , testing will be very difficult.
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FATIGUE ASSESSMENT - 5-N Curves for Welds
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FATIGUE ASSESSMENT - SoN Curves for Welds
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FATIGUE ASSESSMENT· S·N Curves for Pipeline Girth Welds ·
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FATIGUE ASSESSMENT· Applying Addition al Safety Factors to the SoN Curve •
The use of a 'mean·2SD' curve gives a safety factor . • Additional safety rectors can be added to acco unt for uncertainly in design .. detail, inspection prob lems, or consequences of failure. • The choice of this additio nal safely factor is complicated. NORMAL DISTRI BUTIO N
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14
FATIGUE ASSESSMENT - Example of Code Guidance (DNV 1996 - Submarine Pipeline Systems) •
Consider all stress fluctuations (induding during construction).
•
S-N Curve to be used must be applicable 10 malerial , detail and environment
•
S-N Curve must be based on mean curve of log(N) with the subtraction of two standard deviations
•
Th is fatigue strength is furthe r reduced by an 'allowable damage retio : which depends on 'location, accessibility for inspection and repair, inspection stra tegy
•
Norm ally , all pa rts of the pipeline system are 10 be co nsidered as not having acce ss for ins pec tion for fatigue crac ks, and ther efore the fatigue lives mu st be reduce d by a factor of 10 (allowable damage ratio = 0. 1).
•
If an inspection sc hem e can be shown 10 be able to detect critical fatigue cracks . an allowable damage ratio of 0.3 can be used.
•
The fatigue life can be determined usi ng an Eng ineering Critical Assessment. e .g. B S 7910 : 1999, with safety factors applied to defect size.
and consequences of failure'.
THE GUIDANCE ON T HE CHOICE OF THE S-N CURVE IS REASONABLE. BUT IS THE BASIS OF THE ADDITIONAl SAFETY FAC TOR OF 10 REASONABLE?
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ASSESSMENT OF FATIGUE - Fracture Mechanics
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15
THE LINK BETWEEN APPLIED MECHANICS AND FRACTURE MECHANICS - Static Stresses •
Stat ic Strength Des ign (Defect Free) - We design most structures on a streng th (design strengt h equals percent of yield strength) basis. • This design is bas ed on the assumption that the struc ture contains no major defect
• We can base our design on applied stresses and yield strength
•
Static Strength Design (Defect Present) - If the structure has a defect suc h as a crack , we cannot use strength alone to design.
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• W e have 10 use 'fracture mechanics' , which is the part of Applied Mechanics dedicated to understanding fracture.
• Fracture mech anics design is based on
applied stresses and toughness as well as yield strengt h
THE LINK BETWEEN WELD SoN CURVES AND FRACTURE MECHANICS •
An So N Curve for a weld describe s the propaga tion and failure of a weld containing insignific ant defects , unde r specified loading and environment conditions. • The S-N curv es were not developed using cracked specimen s. • The S-N curv es assume only small, insignifICant defect s are present in the we ld
•
If I find, or I am expecting , defects in my weld, that would be bigger, or different from those teste d in the developmen t of the original S-N Curve. then I mu st conside r another approa ch - fracture mechan ics
Use S-N
Use Fracture Mechanics
16
PREDICTING FATIGUE LIVES USING FRACTURE MECHANICS •
If we ha....e a defect in a structure we can pred ict its beha viour with fracture mechan ics. •
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The load ing can be static (causi ng fra cture or collapse), or cycl ic (cau sing fatigue
cra ck growth).
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In fatigue fracture mechanics, we consider ~ a defe ct presen t in a structu re, and 'grow'
the defect using fracture mechanics laws. •
•
The defect grow s under imposed cyclic loading, and we can pred ict when it reaches a size to cause failure .
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Therefore, we start with an 'initial' d efeCI~ (e.g. a weld crac k), and grow it unde r cycl ic loading (e.g. press ure cycles in a pipeline ), unt il it reaches a 'final' defect "-_ _---" size , that causes failure (fracture or collapse).
PREDICTING FATIGUE LIVES USING FRACTURE MECHANICS· Methodologies •
The calculatio ns are well -established, and documented in reco gnised codes such as
BS 791 0 : 1999 or API 579 •
Th e calculations are complex , and require both a skilled engineer, and suitable (but simple) software.
•
The skilled engineer is required to: • ensu re that all the inputs to the calculations are reasonable (e.g. initial defect size) and • that suitable safe ty factors are added to the results, to allow for any uncertainties, and the conseq uences of failure .
BS 7910 or API 579 t?
17
FATIGUE FRACTURE MECHANICS· B asics _ We have consi dere d the failure of 'defect free' stru ctures using the S·N curve. _ However, m ost structures contain some type of defect. Therefore , we need to understand how a crack can grow unde r cyclic loading _ This is called fatigue crack g rowth . and it can be explained and predicted using fracture mechanics , _ The figure opposite shows how a crack increases in r - - -- - - - - - . --, size under a cyclic load of constant amplitu de giving a cyclic stress of 60'. rut _ The cra ck is sma ll (3 1 ) initi ally, and grows in _ fr a.cture a stable, controlled manner un til the critical crack -; size is approached - when crack growth rates ~ !J.a constan t , incr ease and failure occurs. ;: :~ o _ For a given material, the inst antaneous rat e 'of crack gro wth (the slope, daJdN). is found 10 " depend mainly upo n the stress intensi ty range, ,, :~ t"K , (fun ction of stress, defe ct siz e, struc tu re) numbe r cf cyol es, N _This is to be expected as the the near tip f ield (characterised by K ) affects crac k adv ance .
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FATIGUE FRACTURE MECHANICS - Growth of Cracks under Cyclic Loading
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18
FATIGUE FRACTURE MECHANICS - M easuring da/dN
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FATIGUE FRACTURE MECHANICS - Measuring Stresses at Crack Tip
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We need a parameter that represents these stresses. In Fatigue Fracture Mechanics the r.aram eter is 'K' - stress intensity. factor
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19
FATIGUE FRACTURE MECHANICS - daldN versus ~K _ The stress intensity range is the ma in con tributo r to growth rate . W e obtain a cra ck growth curve for each material.
_There are three stages: _ I. In it iaUon Usually iii crack exists, and therefore, the
s1age is zero , • Howeve r, below a lev el (threshold) of M<:
in ~lation
.....e do not hll"'" any crack growth . _ II. Sta b le Pro pa gat i on ,The crack grows in a pr edict able and stable manner. The material characteristic crack growth rate vs intensity range is approximately Iog-Iog linear throug hou t stage 11 10 give:
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FATIGUE FRACTURE MECHANICS - Applicabili ty , p.slIain ---:--.. p.s"""" Conditions for fin al failure approa ched
Fatigue fracture mechanics applies in the linear portion of the curve da ; rl tJ(J"
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IOg AK m is variable , it is typically 3 for structural steer: 3 is o ften used for aluminium allo ys , but m ca n be higher. A typical value for C in struct ural steel is 3)(10-13 N/mm-1112 (for leng th measured in mm ). No te tnat daldN" 0 when a K below the thresh old .
20
FATIGUE FRACTURE MECHANICS - Calculation
(ilK) • To calculate the fat igue life (N) of a known defect using fatigue fracture mechanics we will need to know: • the cyclic stresses, ~cr • the initial defect size (either assumed, or measured), a • a 'Y' calibration for our cra ck and structure, and • C and m for our material, environment and stre ss level. • These allow us to calculate the cyclic stress intensity factor:
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FATIGUE FRACTURE MECHAN ICS - Calculation (Paris Law) • We generally use the 'Paris Law' for the whole range of da/dN (this is conservative at low K, and only a small • amount of time is spent at high K):
da =c(L1Kt dN • At low K, we have a 'threshold', where the crack does not grow (analogous to the endurance limit). • Typical values for welds are: Meo = 63 Nrnm ? " , R > 0.5 M o=1 70 -214 Nmm · 3-2 .0 :::;R 5:0.5
M o = 170 Nmrn?" , R < 0.5
21
FATIGUE FRACTURE MECHANICS - Calculation (Growth)
do dN M( =
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Integra ting gives
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FATIGUE FRACTURE MECHANICS - Final Defect
Size •
The fatigue calculation is complex as it generally requires numerical integration (or some other form of iterative solution) to calculate e a.
•
We will also have to calculate the defect size at which the structure foils - this will defi ne the 'final' defect size (a,) in our fatigue calculation. • This calcu lation will req uire a failure analysis (e.g. using BS 7910 : 1999 or API 579)
22
FATIGUE FRACTURE MECHANICS - Example EXAMP LE Co nsider a flat metal plate under repeated tensilecom press ive cycling in which the mean stress is 25 MPa .
=
If: 8 0 0.25 m m , ac = 5.0 mm , m 4.0 , A 5 . 10.15 , Y 2.0, and N, =3.2 .10 5 cycles .
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FATIGUE FRACTURE MECHANICS - Calculations for Pipeline Defects •
lf we have
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det ected a defect in a pipeline we follow the procedure we have summ arised earlier.
• '\. M
•
If we do not know the initial size (a<> of a defect in our pipeline , we ca n still estimate the fat igue life of the pipe line . by assuming a defect is present in ou r pipelin e that has 'j ust' survived the pre-s ervice hydrotest (for an axial defect), or 'j ust' surv ived the laying pr ocedure (for a circumferential defect, e.g . in a girth weld ). etc.. • This will be a conservative approach because the defect we are assum ing is hypothetical. and is the largest possible.
•
Th e final defect size (af ) is calculated using an approp riate fai lure crite rion, e.g. the Battelle part wall failure criterion for axial defects. • The final defect size will be calculated using the max operating pressure (toaxial defects) , or max axial stress (for eire. defects) in-service .
.. 23
FATIGUE FRACTURE MECHANICS - Calculations using a 'hydratest' defect HIGH LEVEL HYDROT EST (e.g. 105%SMYS)
LOW LEVE L HYDROTEST (e.g. 9O%SMYS)
I~
I.
l-
'---
1 HYDROTEST 1
__~~~~_I ____
~_ _
I
OPERATION
FATIGUE CRACK GROWTH
_
__
I_~~~~
I
L!".
_
Therefore, a high level test ensures tha t a larger margin for defect growth is avai lable, and hence a longer fatigue life.
FATIGUE FRACTURE MECHANICS - Calculations using a 'hydratest' defect 11" ,<1/
Note that not all defects are 'credible', For example, a defect of depth of 99 % wt being present prior to the hydrotest is incredible . More credible defects are long shallow corrosion (from poor storage ),long shallow scratches, axial weld defect related 10we ld geometry. process. mill lest and inspection limits, girth we ld defects related to inspection limitations during construction, etc ..
24
FATIGUE FRACTURE MECHANICS - Final & Initial Defect Sizes for Axial Pipeline Defects
1-
Gj
t
(JII YDROTEST _
-
1- Gj _1_
(J
t M where
a
=
if
=
a
=
t
=
M
=
hoop stress flow stress defect depth pipe wall thick ness Fo nes factor (bUlgi ng factor)
~_2OClI _'
"
FATIGUE FRACTURE MECHANICS - Final & Initial Defect Sizes for Axial Pipeline Defects
~
01
~ 01
"
of ~
01
OPERATING PRESSURE (72 percenl SMVS)
l os .. u
~
OJ
erectssurviving
~ :~ r"'1
grow to
. .. r:
O_2OJt_
I.", "
HYDROTEST RESSURE (100 percenl SlAY ) I
I
.. .. .. .. .
••
2c1(Rt)"O.5 (nonnalised def ect length)
se
25
LINKING SoN CURVES AND FRACTURE MECHANICS
LINKING SoN CURVES AND FRACTURE MECHANICS
• •
In (fatigu e) fracture mechanics we will model an initial defect size , and then im pose cyclic loading onlo this def ect.
•
.
II will grow 10 a size that will caus e fa ilure.
An S-N Curve for a we ld does the sa me th ing . •
~~/
The we ld will ha ve sma ll defects in its surface (e.q . slag intrusions at the weld lo e), and this 'initial defect' will grow under cyclic loading .
• It will eventually reach a size 10 cause we ld failure.
•
Th erefore, a we ld S- N curve is me re ly an experimen tal descriptio n of crac k growth and failure in a weioment . whereas frac ture mechanics is an analytica l descrip tion af the
same event.
• " - 2001_611
I~•
"
~~ Cytieo, N
sa
26
LINKING S·N CURVES AND FRACTURE MECHANICS •
The problems we have in com paring the two app roaches (and obtaining agreement in observed and predic ted fatigue lives) are:
• we do not know the size or locat ion of the small 'initial' de fect in the weld , • it is very difficui l lo mode l small defects with fracture mechan ics , • it is di fficult to calculate the stress co ncentra tions in we ldmenls, • it is difficult 10 modellhe re sidua l stress fields in the we ld , and the growth of
a crack through these complex fields, • all faligue testing is prone to scatter, and any comparison between theory and expe riment would require extensive lesting and ana lysis, and • we may nol be comparing the same type of failure , e .g. an S-N cu rve may define 'failure' as first indication of crack ing, whereas a fractur e m ec ha nics an alysis may use complete failu re.
0_2005 _
_
LINKING SoN CURVES AND FRACTURE MECHANICS - Comparing Predictions
SoN curv e for a
u1
/""
~
seam weld
/
~
w w
~
LO WER BOUND
:;; o
~
.>
~
Fatigue curve ca lculated using fracture mechanics. with the hydrolesl level to define the initial defect size NUMBER OF CYCLES
0_2005 _
_
27
SoN CURVES AND FRACTURE MECHANICS Safety Margins in SoN curves •
In S-N Curves we have man y unknowns : • thei r origins ma y not be known (type of specimen (wel ded or plate ), th ickness , env ironment, treatment (e· 9· grinding ), etc., • weld qua lity , and inherent de fect s may be unknown , • the tests will have been conducted over a limited cycle range , and extrapolati on may have been necessary in low cyde reg ime , and very high
cycle regime, • the tests will have used simple (tensile or bending) constant amplitude loading, whereas re al structures will have a complex loading spe ctrum , • differi ng failu re criteria are used in tests, e.q. cyctes to first indication of cracking, or cycl es 10 com plet e severance,
• etc.. •
• • •
So me 'unknowns' will be included in the S-N curve (e .g . mi salignment). However, an unknown such as misalignment is likely to be la rger in a rea l structure compared to a laboratory specimen, When we apply our S-N curve to our struc ture we use the 'Miner' rule to deal with stress spec tra; this rule can be inaccurate. W e are trying to pre dict the fut ure behaviour of our stru cture . Therefore , we ad d further sa fety margins onto our mean-2SD S-N curve.
SoN CURVES AND FRACTURE MECHANICS Safety Margins in Fatigue Fracture Mechanics •
•
• •
In a fracture mec ha nics calculation we have less un kno wns , as we know : • the defect pres ent, • the stress field , • • the size of the structu re . etc.. We can also include or model: • un certainties in shape, e.q . misali gnment • fa ilure, • en vironment, • complex loading , etc.. Fatigue frac tur e me cha nics still ha s unce rtain ties (e.g . the select ion of the crack growth cons tan ts C and m ), and sa fety factors must be applied . The fatigue fracture me cha nics calculations in BS 7910 : 1999 re comm end safety factors on certa in parts of the fatigue calcu lation (e.q . a minimum safety factor of 4 is required on the parameter C), but it states that the use of its reco mm ended constants will give a survi val proba bility correspondi ng to 97 .7%, l.e . the same as a mean -2SD S-N curves . • No add itio nal tecto- of sa fety is exp licit ly stated .
28
SoN CURVES AND FRACTURE MECHANICS· Should My FM Calculation Predict My SoN Curve? •
SoN Curve • My SoN curve has used ma ny welds: • containing a certain type , numbel' , shape
and size of ('in ilia!' ) defects • having various stress concentrations - -(SC Fs) due 10 m isalignment, etc. • certain cyclic stresses, applied in the laboratory • (usua lly) of unknown qual ity, strength and touqbness . • an d the curves will ha ve been plott ed using regression methods, and lower bounds.
•
L)
I -
-
~------
Fracture Mech anics calculation •
My FM calculation requ ires exp erim entally derived parameters (C and m), an acc urate measure of the initial defect size. good me asures of SC Fs and applied stresses and knowledge of materia l properties such as tough ness and yield strength
log ""
SoN CURVES AND FRACTURE MECHANICS Should My FM Calculation Predict My SoN Curve? •
Agreement? • If my fracture mechanics calculations can model all the above, and if my fracture mechan ics calculation has very accurate model parameters, the n I should obtain reasonable agreement.
•
Likely? • It is unlikely that I will be able to mode l all the above , and accurately predict an S-N Curve , un less I conduct ma ny calculations, or I hav e exact da ta fro m the tests that made up the S- N cu rve .
,! !
l O WER BO UNO
g ,
< n
_
, '
~
._
..
m-..",• ... ,n.
_ .,
0"'" .'..
29
SoN CURVES AND FRACTURE MECHANICS - What if my FM Calculations Predict Longer Lives than my S-N Curve? •
If you are ca lcul ating the fa tigue life of de fects la rg er than those allowed in a we lding (wo rkmanshi p) specmceuon. you expect your fractu re mechanics ca lculations 10 pred ict shorter fatigue lives tha n the S-N curve.
•
Howe ver , reme mbe r to be consistent. •
If you are co m paring you r fracture mecha nics calculated fatigue life with an S· N curve, the y m ust co ntain the same safety fac tors.
• There is no point comparing a mean-2SD SoN curve to an accurate fracture m echanics calcul ation. •
II is basi 10view an S-N curve (without safety factors) as the maximum life you would obtain from a fracture mecha nics calcu lation, under ide ntical load s and geometry, as the S- N curve will be ba se d on specimens with sma ll defect sizes.
•
Unless you improve the fatig ue strength of the we ld (e.g. by toe gri nd ing), the fatigue lives fro m the S· N curv e can no t be exceeded using frac ture m ech an ics calcul ations.
O~2IXl6_
SoN CURVES AND FRACTURE MECHANICS - Small Defects •
SoN curves of we ldme nts are a good description of the fa tigue life of that weldment when it co ntains defects (e,g . sm all slag int rusion s at a weld toe) tha t .. ar e not readily detected by conventi on al non-destructive inspection,
•
The y ar e equivalent to fatig ue fra cture mech ani cs ca lculations of the we ldmen t using very small initia l defects (e.g. < O.5mm deep).
•
The re is no requirement to app ly the same saf ety factors to fatig ue lives usi ng S·N curves or fracture mech anics .
•
Safety factors should be induded to accommodate uncertainties in each of the approa ches.
30
GUIDANCE IN DESIGN CODES FOR ESTIMATING THE FATIGUE LIFE OF A PIPELINE Both 8 5 80 10 and lG EfT D/ 1 have guidance on fatigue. A limit of 15000 cycl es , al a maximum daily variation in hoop stress of 125 Nfmm2 is quoted. Smaller and larger stress range s are allowed . The num ber of cycles at the specified stress ranges are factored (multiplied) by this factor C. The sum of factored and unfactored cycles should not exceed 15,000 cycles. - . R.nge (WWlon'l
h oot... C
'~ · 'M· 125 - 145'
2.5' 1.5'
105· 125
1'0· ' 05 )5·10 O- llS
.r - tOIO _
fWlIIeS ..., tBcIcn
U 0.2 0
are ~ in IGE TDi1. bUt nol in as 80'0
The fatigue life of a pipeline , as given in the above table . is based on the assumption that a delect survives the high level pre-service hydrotest. This defect can then grow du e 10 fatigue cycling. The limit it can grow to is dictated by the maximum operating pressure. Consequentty. the above table assumes a high level test , and the stress cycles as given. The cal culations use basic fracture mechanics laws (validated against experiments), with a safety factor of 10 to accommodate the uncertainties associated with these type of calcu lations.
"
DEALING WITH COMPLEX CYCLIC LOADING
"
31
DEALING WITH COMPLEX CYCLIC LOADING •
l oading on a pipeline will not fo llow a 'regu lar patter, such as a single
Stress
rfl
pressurerange, over a constanttime _______ period. •
• It will be complex Therefore , we need to be able to analyses and simp lify complex loading histories , and then use the simp lified ""history in our S-N analysis, or fracture mechanics ana lysis \
'.
I
j -
J--.
'vv
"'- ,-_.....,.
,.
!.
I
r ROO "
;' •
X tr-
-
•
-
-----,,----~- ~-~-
COMPLEX CYCLIC LOADING: 'Cycle counting' •
We need to simp lify comp lex load histo ries into a
numberof stress ranges and cycles
•
c_
•
We use met hods called 'ralnflcw' or 'reservoir' m ethods to do this.
•
These methods require software
comple x cycli c loading
In the Reservoir method : •
Complete stress (or load) cycles are counted using this met hod.
•
The stress wavefo rm must be expresse d so that it starts and finishes at the same value. which must be the ma ximum peak .
•
The wavefo rm is cons idered to represent the profile of the botto m of a reservoir filled with water.
•
The way in which the wate r would empty from the reservoir as successive troughs are drained defines the cycles to be coun ted.
•
The height of the column of water that is dra ined defin es the stress range.
- - - - - - - - - --
t ime
one cycl e ma ximum v alue
minimum value
sIm ple cyc lic load s OOOB R0V6/1
32
RESERVOIR CYCLE COUNTING METHOD
Ima gine tha t a hole is made in the deepest trough first.
1. The first cycle is defined by the d epth of water thai is drai ned ou l by that operation giving the stress cycle represented by d 0 1 . 2 . The next deepest trough is t!'len dr ained. giving the stress cycle: AO":. and so on , counting a stress cycle a fter each
trough has been drained until the reservoir is empty.
d eep er
time
es
COMPLEX CYCLIC LOADING: 'Miner's Rule' •
Now we need to change these many stress ranges one eycle and cycles inlo a single stress range and single number of cycles, to allow us 10 use a S-N curve, or simplify our fractu remec hanics crack growth calculation •
We use the Palmgren-Miner's rule to do this.
•
We a ssu me that the 'd amag e' at a given stre ss level is eq ual to the 'c yc le ratio'
•
The cycl e ratio is the ratio of the number of cycl es at a giv en stre ss lev el, n, to the faligue life in cycles at that stre ss lev el, N :
n n ' + _n 2 + ... + _~ ~l N1 N 2 N~
or "L -n'
, Nj
~I
mulmum value
minimum valu e
----- - - '-'.'-. simple cyclic loads
-
Stress
• n, '" no. of cycl e s at a give n stress range • N, is expected fat igue life at tha t stress lev el •
Failure is assumed tc occur when this sum >=1 si ngle cyclic load
33
COMPLEX CYCLIC LOADING: Summary
COMPLEX CYCLIC LOADI NG
-
CYCLIC COUNTING METHOD
reservoir cyc le counting
II number of indIvidu al
rain -flo w cycle c oun ting
cycl es of diffe rent ranges
MINER 'S RULE II number of cycl es of II s ingle stress ran ge
0_200II_
1.
S-N CURVES, or
2.
FRA CTURE MECHANICS
"
•
34
Fundamentals: How to Assess Defects in Pipelines
Penspen Integrity
'
eM
1
INTRODUCTION
2
ONSHORE DATA: USA, 2004 •
Defects fail pipelines
Nole ,..... 0f'S .....
"""" 001""';sed
""""9"" do" ;.
load
INTRODUCTION: Fracture Mechanics •
•
•
•
•
Fracture mechanics is t he science and mode ls of the behaviour of defects in structures It is used extensively around the world, and in most industries It forms the basis of all the methods we use in pipe lines. However, we have developed our own methods over the years , wh ich have taken the comp lexity out of the calc ulations. But t hey are still based on fracture mechanics
acture
Science Gene ral Codificafion In Pipelines Codes
8 8 1791 ASME 831
Specific Guidelines
e
ies
A 1579
•
104
NIJ: GS F10
CSAZ184
NV RP F10
A
B es t Practic es?: Corrosion Gouges Ginh Welds
Crack Prop.
NEVER ASSESS A MESSI • Fracture mechanics can help you assess defective structures. but you CPM...., 2OIl! should not apply illo slructures Ihal are dearly unsafe, or have been badly designed , built Of operated.
4
2
INTRODUCTION: Defect Assessment •
•
FIRST•.• GOO D DESIGN ! - All engineering structures should be design ed. built and operated 10 a recog nised code or stanoarc.occesionany. defects occur in these structures, but. .. • Defect assessment IS NOT A SUBSTITUTE FOR GOOD DESIGN , BUILD O R OPERATIO N - IT IS COM PLEMENTA RY ASS ESS ALL PO SSIB LE FAILURE MODES : • Fracture • Fatigue • Yielding or plastic coll apse
• l eakage • Corrosion ancl erosion • Stress corrosion cracking and corrosion fatigu e • Buckling • Creep and creepJfatigue • Often, a combination of failure modes needs to be considered . 5
INTRODUCTION: We are assuming 'ductile' materials •
We will consider 'ductile behaviour" in this presentation
Ener gy Absorbed
'Impact' toughness specim ens are used 10 plo t these curves
lower shelf (BRITTLE) Tem perature
_ _ 2001 _
1!11
-c..ew.lracue"_
Ill. ......... Iion, grootAA _
~
01 _1hNcl 01a. cno
~nctlft ·_lhe--"of~,*,,"of_by"_ .
6
3
MEASURING 'DUCTILE' & 'BRITTLE' BEHAVIOUR: DWTT •
We use a 'drop weight tear test' (DW TT) specimen to dete rmine if line pipe is ductile or brittle
O_:IOOI_&,1
...
_---- - -
r
MEASURING 'DUCTILE' & 'BRITTLE' BEHAVIOUR: Charpy •
We use a 'Charpy' spec imen to measure the (ductile) toughness of line pipe IF
•
/
O_2OJI_lV'
" .I'IoJ/
8
"'
4
POSSIBLE LOW TOUGHNESS PIPELINES Modem line pipe steels are ductile. and failure is generally cont rolled by the yield strength or 'plastic collapse', not brittle fracture. The following applications MAY be susceptible to brittle fractu re initiation. Materia ls manufactu red prior to 1927. Any material that has been show n to have a fu ll scale initiation tra ns it ion
te mper atu re above the operatin g te mper at ure. Material of thic kn ess greater th an 12.7 m m, unless the fu ll scale ini tia tion tran sition tem per ature is below the oper ating t empe rature. Def ects In mechani c al joints, fab ricat ed , f orged. f o rmed or cast fittings and attached app urt enances. Def ects in bond l in es of flas h we lded (FW) or low fr equ ency elec tric res ist an ce we lded (ERW) butt-we lded p ipe. O lder Stee ls : ' Lap welded' or 'f urna ce butt we ld ed ' pipe ; 'Sem i- killed' st ee ls (o lde r steels th at did not rec eive modern proces si ng).
0_2001_""
IlO5Ulf~W"'.J.KUo.vvf. ;~f_"'","-_""'A$UflU'Coolt ... _ """"v_8:l,.c.r _ _ .. _ ............_ ~.,,
9
LINE PIPE FRACTURE BEHAVIOUR
0 _ _ 2OOlI_""
5
FRACTURE: 'Initiation' and 'Pro pa g a t io n'· _ A defect in line pipe can fail by 'initiation' then 'propagation' . 'Initiation' refers to the growth of a defect under rising pressure, cyclic pressure, constant pressure, and environment, to the point where it penetrates the pipe thickness and produces a leak or a rupture. • 'Propagation' refers to the rapid axial, or in high secondary stress conditions, circumferential, extension of a fracture once it has initiated or penetrated the pipe wall
cl_2\lOII_'"
_.,_._0-'_ .
-. . . ""'- _
11
FRACTURE: 'The 'Transition Temperature' DUCTILE
. The 'transition temperatu re' is the temperature at which the fracture mechanism changes from ductile to brittle ,]
•
~• ~ • •
tr ansiti on temperature
BRITTLE temperature
Brittle
-- _ .....
...
_
~
..., .
..",
.-....... .
""
tz
6
FRACTURE: ' FITT' and ' FPTT _T he fra cture 'initiation' transition tem perature (FlI T) is the tem perature at wh ich th e fract ure 'initiation' mode changes. _The fracture 'propagation ' tran siti on temperature (FPTT ) is the tem perature at whic h the fractur e 'propagatio n' m ode changes . e
...
FPTT FITT I
,
,t1---
I
I
-'"
0 o
TFPTT is
0 o
greater th an T FITT
'
temperature
::
initiation
- ; - --
-
. propagation
ta
FRACTURE: The 'FITT" _ T he fractu re initiation trans ition temperature (FlIT) is the dividing line. where the fractu re initiat ion mode changes from ductile to brittle, as the temperature de creas es below the FITT.
•
Ductile
_ II depends on loading ral e on the defect (see ne xt figure) _ It depends on the type of defect
I0
_ It depends on the thic kness of the structure
_.
'.::: .-,_ . ~
~
_.- ChaIopy
O_2llOOl_1II' _.j ' _
~
.
FITT
Temperature
Drop W eigh t Tear Test (DW TT) specimen "_C-'-.., " . :»II. ""' ,.,
7
FRACTURE: The Variables
)• ~
~ o
throug h-w all defect
•
temperature
tem per ature
-e
-1!o
also, decreasing thickness in Charpy or DWTT specim en
11
•
~
•o •
-... . _. ..
C_2OOI_..'
temperature
""'"_
"
_-.-~--
FRACTURE: Using 'OWTT' specimens to determine
'FITT'· _ For mo st pipelines, the FITT can be estimated from 'DWTT' curves . _ Early work indicated that the FITT is - 330C* below the temperature for 85% shear area on a specim en. _ But note that work by Battelle" has
A
DW TT test spec ime n (fla tte ned )
F
own
1°°1- - - -
Charp;:'-notch
test specnn en lhe or ientation of tom
specmens 's the same
I
shown thalia ensure failure of a 85% defect is governed by the UTS of the mate rial, a typical toughness (full size Charpy) of 60-75 ft Ib (8 1-102J) is
needed. _ Not e that these levels need to be calculated. and that they wiDens ure collapse at the UTS (which is higher than ue conventional stress we use in our equatiOOs - se e later)
now
-
0_2001_ .. ' _ ., . .... .. ..
....
~_e-.o
T
_ _ .. - ..
"""'_ ........ " .....-.'-
O L- . - ...... T
FITT
--~ ~_
------JL---=-_ Temperature
.."'""_.-. "- .-:.,,~ _ _ .... _
......,
-
8
FRACTURE: Using 'DWTT' specimens to determine 'FPTT'* _Full sca le tes ts have shown DWTIlest specimen that the DWTT can be used to (flattened) predict FPTT. F _The FPTT is typically taken as the temperatu re at which 100 1- - - - the DWTT fracture appearance is 85% shear. 85%
]
m "
•
s:
-'--------=_ _
0 '--
FPTT
Temperature
C Ponspon 2006 R"" 611
17
ENSURING DUCTILE BEHAVIOUR: Using 'Charpy' specimens· _ Recent work' investigated corrosion in low
S
toughness pipe _ It used 'FPTI' (defined in the work as the temp. co rresponding to 85% shea r area on a Charpy) _ 'Rule of thumb' is thai carbon steels operating >60 oF below the FPTI may be susceptible 10 brittle fracture • II was concluded: _ from tests {on steels at tempe ratures up to 208°F below FPTI). and e servtce experience
E
"g
c% ~
a.
B
_ thai ducti le behaviour can be expected al temperatures below the FPTI
'FPTT'
_The w ork concluded that current corro s io n ass essment methods could be applied to line pipe made after 1947, assuming the FPTT is not excessively high a s erecnve corrosion In old ERW matenals IS an
Temperature
exception C Pon-,2006 R&>' 6Il
·Soo ",_ ",__ __ ""' '''''C-..''''' "_ "'CO«>'" . ~ ",
~'""l_""E""''''',,,~_
18
9
HOW A PART WALL DEFECT FAILS
ts
0_2001_&11
HOW A PART WALL DEFECT IN A PIPELINE FAILS b.• tt
l
• p ....... _ " " .
'9""'
Pa rt Wall Defect
' ' ,
_ 'n ""'_~_."' ,i
_
.... . ." ....
001"" '...
_ ~ . T h ro u g h-Wa l1
......,_ ....,......
"l
Defect
' r ~I ~A T_ W" """'''. _
...... ._.-. _w..........-..
Leak
. .__w .__.. _-._. . . propa9ales~=~~ I ,..
0_2001_11'
_._r ~
__
~=~~::::::'3'\~~[~:;= 20
10
- - --
-
EARLY WORK ON PIPELINE DEFECT ASSESSMENT
o
p ",, ~
2000 flov 6/1
21
BACKGROUND TO METHODS FOR ASSESSING METAL LOSS DEFECTS - Early Work •
The methods we w ill describe for assessing pi peline defects are based on research wo rk undertak en at Battelle Memorial Instit ute (in the US)
•
In the 19605 and ear ly 19705, Battelle (on be ha lf of the Am erican Gas Association (AGA» conducted. • Over a 12 yea r period , up to 1973, ove r 300 full scale tests were completed .
splpe length
• 92 tests on artificial th rough wa ll defects • 48 tes ts on art ificia l part wa ll defects (machined V-shaped notches)
22
11
--
BACKGROUND TO METHODS FOR ASSESSING METAL LOSS DEFECTS - Tests th rough-wall defect
_Battelle developed:
a'semr-ernoocar failure criterion for through wa ll defects
esemr-empmcer failure criterion for part wall de fects
. . . ' : \ . \.. ;p ,'-,,---,
.
..............
part-wa ll defect
\~\:'/
BACKGROUND TO METHODS FOR ASSESSING METAL LOSS DEFECTS - Failure Mode
•
T he Battell e wo rke rs noted that line pipe with defects failed in tw o ba sic ways : • 'Bri ttle ' ('toughness dependen t) - these tests failed at low stress (pressure), with low deformation. To predict the failure of these tests you needed a measure of materia l toug hness . • 'Ductile' ('strength' dependent) - these tests failed at high sires s. with deformat ion. To predict the failure of these tests you needed a measu re of material yield strength . DUCTILE
•
Fortunately, most line pipe (certainly that bought to a good modem standard , e.g . API 5L ) failed in a ductile manner. This is good, as failure is preceded by deformation , and failu re is at high stress. • Very old, or poor quality line pipe could fail in a more britl!e manner
O~:lOO6_1!/1
S IreSS
-
FAILURES
DEFOR MATIO N
"
BRITTl.F'
"
12
BACKGROUND TO METHODS FOR ASSESSING METAL LOSS DEFECTS - Failure Mode •
A ductile burst failure has a disti nct bulge at the burst
location. • A longitudinal fracture extends over the length of the bulge and terminates near the end of the bulge . •
Ductile
The end of fractu re tums at
Figures from API 1111
roughly 45 degrees from the pipe axis at each end. •
The failure surfaces have sharp edges
Brittle
25
BACKGROUND TO METHODS FOR ASSESSING METAL LOSS DEFECTS - Dependence on Toughness Very old, low toughness line pipe & welds are not covered by our fund amental equations.
•
~
1.3
tI)~
Scatter
ill'" 1
.:::
(JJ
~~ K S~ ~ ~
~ ~ §:o
13
e
o c l _ 2 O O I _ s-1
Toughness
0.8
Strength Dependent
+--
Dependent
I
- 27J* (FuJI Size Charpy) (20 n ib)
Toughness "Thio ~_ Ilean"_ $hlIlf ~ .• _e~""""lhebnc _ _ IhouklIle"'"
26
13
BACKGROUND TO METHODS FOR ASSESSING METAL LOSS DEFECTS - Dependence on Toughness
.." .... .. .... "
, "
Toughness
Strength Dependent
Dependent
.. " ..
"
I
0 '-O_:!tIOG_&,1
-27J (Full Size Charpy) (20 fl lb)
_ Toughness
BACKGROUND TO METHODS FOR ASSESSING METAL LOSS DEFECTS - Theories • Many other organisations have since conducted tests to confirm the validity of the Battell e workers pioneering resea rch. • The early work compared the measured failure stress of pipeline defects with that predicted using various for mulae proposed by the workers. • If 'predicted' by theory = 'measured' from test , then the theory was good .
28
14
BACKGROUND TO METHODS FOR ASSESSING M ET A L LOSS DEFECTS - Test Results r-
-'~i- BaItelle Tests
Predi cted Failure StressIyiekl Slrength
('lloJ
•
• •
• •
•
•
Non-conservative prediction
•
••
Conservative prediction
..
o ..
~ ~
_ ,,,,,,,,,,
_
..... .. ~
. . . . - -
Meas ured Failu re StresSIyieId strength ('%) C_20J5_...
29
FAILURE OF A THROUGH WALL DEFECT
•
O_2006_lIIl
30
15
THROUGH WALL DEFECTS: Leak or Rupture
C_2OlI_'-'
THROUGH WALL DEFECTS Defect Dimensions _ First of all we will consider the 'through-wall' defect in a pipe line. • Yes, this is a leaking defect. so it is not a practica l defect to
o
'assess '. _ However, it is sim ple, and . when we assess a through wall defect we are assessing it to see if it will remain a 'leak' (no fai lure) or 'rupture' (a failu re)
-_. ..-
",,-_"'_~dEt>v_
O_2C05 _lVI
32
16
THROUGH WALL DEFECTS Defect Dimensions through-wall defect
I (or 2c)
'I
1
I (or 2c) t
~
""
•
"= I I _ww
= =
defect axial length pipe wall thick ness
O_2OOIl_1II1
33
THROUGH WALL DEFECTS - 'Bulging' •
W hen a throu gh wall defect is pressurised, the tips are highl y stressed, due to: •
the lack of a hoop stress along
the length of the defectto resist the inte rna l pressure, and •
re sistance 10 bulging .
High stresses C_
2OOIl_lIl
17
THROUGH WALL DEFECTS: 'Bulging'
Defect bulges outwards before failure
<, FLUID PRESSURE This bulging plays a major role in the defect's failure. so we wi ll need somemeasure of it.
o_:ruoa_ ..,
35
THROUGH WALL DEFECTS - Failure Equation
-OJ =M1 a
~?
""-? .
(,. ......
..
'".......:
where
= hoop stress (a o) in pipeline when through-wall defect fa ils = flow stress So . we need to understand : = Folias factor (bulging factor) . Folias Factor _Flow Stress C_
2OOlI_ ell
18
THROUGH WALL DEFECTS - Folias/Bulging Equations
e
_ It quantifies the bulg ing we see around a defect in a pipeline. as it fails under pressure loading. _ It is a stress amplification at the ends of the defect _ The longer the defect, the larger the bul ging _ There are various approxim ations to Folias' solution:
M
{2c '
1 +. 0 4
=
..
"
~
~+.:
Early lower bound
v=RI ru
a pprox imation Devel o pe d from Theo ry (most precise)
Where:
At =
i
2c
1+ O.2"\. JRi
z I"--- -~_ Lo wer bo und
= = =
2c
t R
defect axial length pipe wall thickness pipe radius
ap proximation to above
O_2OOII_lIIil
THROUGH WALL DEFECTS - Folias/Bulging Graphs
M"
"
The longer the defect, the larger the bulging
00
00
00
00
00
00
. ..
..
..
..
..
o.
••
'u
..
2c1(Rt)o.5 (normalised defect length)
. 2c1(RI)05 is a sln .ple way of plotting 'normalised' defect length . _ This 'normalised' leng th has no units, and allows us 10 produce plots for any 'R' and 'r. in any units .
~. -' :..........=..-
J8
19
THROUGH WALL DEFECTS - '2c/(Rt)a.s,? . Wh at does '2c1(Rt)05' mean? . '2c· is the length of the defect. . 'Rt' is the pipe geometry. For examp le: . If R = 12 inches... t . (Rt)O.5 = 2
=0.33inche s... Rt =4
. '2c1(Rt)O.5' = 2c12 . So.. . if I have a 6 inch long defect in a pipe of 12 inch radius and 0.33 inch wall thickness... '2c1(Rt)O.5· = 6/2 = 3
39
THROUGH WALL DEFECTS - The ' Fl o w Strength' •
T he flow stress is an empirical conc ept.
•
It was introdu ced during the early work by Battelle on the development of failure criteria for part wall and through wall defects in pipelines, as a m eans of taking into account 'work harden ing'
"
PLASTICITY
'WORK'
HARDENS
NECKING
ELASTIC
• As the stress increases above yield strength. the ste el har dens as it deforms. and can withstand more loading. • W e can view flow stress is when pla stic flow begins arou nd the erect
~_ ;I(l(lII _ ""
"
20
THROUGH WALL DEFECTS - The ' Fl o w Strength' Stress (0)
typical enginee ring stressstrain CUNe fo r line pipe steel
e ng jnee ring
. ultimate •• .••••• ----:;;;--;;--;o--~-~ tensile ./ strength yr>'''-- - -
yield strength
--
~ - - - ---'''''''" ,.---~
----- flow strength
"
elastic-perfectly plastic
material
Strain (el _Battelle used fractu re mech anics to develop a fai lure criterion, assu ming an 'elasticperfectly plastic' material. Howev er, line pipe steels exhibit work hardening . _As a means of approximating work hardening in a single parameter, the concept of the flow strength was proposed.
THROUGH WALL DEFECTS - The 'Flow Strength'
YIELD STRENGTH
'->
I
· ·f·m:!I!~
..
t he fl ow stress is somewhere between t he'"' yield an d tensile strength
/
~! FLOW, ~ STRESS?
TENSILE STRENGTH
P
0 _ _ _ ....
"
21
THROUGH WALL DEFECTS - The 'Flow Strength' • Th e flow strength is not a precisely defin ed term • it lies somewh ere between the yield strength and the ultimate tens ile strength of the mate rial .
• A number of different defin itions of the flow stress have been proposed • They often depend on what fo rm gives the best fit to the experimental data. • The following have been quoted in the published literature:
. o-y + 10 ksi _1 .1 0"y _1.1 50"y _ (O"y. 0", )/2 . 0 .9 au
"'
---
.. ....... . :.: .. ...~ .. - - -{
- - flow strength
C POMpM 2006 Roy 611
THROUGH WALL DEFECTS - Failure Equation
HOOR stress at f~ilure,
O"{;
r--;=~-=-~ I lTy
M =
1 + OJ 14
2C)' - 0.0008 4 (-:j'ii; 2, )' (--:nr;
==M-1 CL
.>
+ 10 ksi (+ 68.95 N.mm· 2)
1.1ay 1.15 a y (ay ..O"ull2 O.9au
"u
Or, we can plot this as a curve ... CI_
","" 2006 Rov6l1
22
THROUGH WALL DEFECTS - Failure Graph ThiS lea k rupture boundary is net sens itive to preS$uri$ing medium
cor
"
RUPTURE LEAK
,
•
2c/(Rt)"O.5 Th., "' '''
1 .' S. ~ ..,
_
um.. . """ .".."
ot
THROUGH WALL DEFECTS - Failure Equation • What does 'hoop stress at failure' mean?
• The predicted failure stress (a r) is simply the hoop stress in the pipeline that will cause the defect to fail. • The nominal hoop stress in the pipeline is a o and is equal to pD/2t. • So... if my predicted failure stress (a r) is 400 N/m m' , then the hoop stress (a o) to cause failure is 400N/mm'. • If the hoop stress 0' 0 in my operating pipeline is < err then the defect in the pipeline will not fail. • If the hoop stress a o in my operating pipeline is ~ a r then the defect in the pipeline will fail. • I calculate my failure pressure from my failure stress by:
• PI = a,2t1D
23
THROUGH WALL DEFECTS· Summary
"
T~i. boundary is J>ol
$OO I'li"" t
[J
~J=n
O_~_&l '
THROUGH WALL DEFECTS Example No.1: Calculation
_ I find a defect that is through my pipe wa ll. _ It is 6· in length (2c) (remember it is through wall so its depth is 100% t). _ The operating pressure (P) is 834 psi . Operating stress 30,OOOlbf/in 2
(J
=rr =PDl2 t =634x36/2xO.5 =
_ W ill thi s thro ugh wa ll defect eithe r leak (no fai lure) or rupture (fail)?
0_2005_611
"
24
CY f
THROUGH WALL DEFECTS Example No.1: Calculation
t
36" Diameter (2R) • 0.5" t, X60. Operating Pressure
. Defect = 6 inch in length (2c),
=834psi
Operating stress = 3O,OOOlbflin 2
8 1want to calculate the failu re stress of my defect. 0'1 8 1f operating stress < Of the throug h wall defect will not failu re (it will 'only' leak ) _ If operating stress> of the through wall defect will fail (it will ruptu re)
- cr= 1.15x600oo =69000 ibffln'and
2rJfii.i = 6/ ;;8xO .5 = 2 therefore M" =1 /1 .43 0.7
_ M P/"1 ... 0.26 (2}2 = 1.43
=
- ala = 0 .7. therefore, 0", =69.000 x 0 .7 = 48.3101bflin2
=
= =
8 Failure stress a t= 48,310 Operating stress 0"9 30,000 ap oa 8Therefore, t his throug h w all defect will not fail (it w ill ' only' leak and it will no t ru pt ur e). e
I/,
THROUGH WALL DEFECTS Example No.1: Calculation using Graph
. .. M-l .. .. .. ..
ft.
_ From previous page. 2cl 2 _ From this graph I obtain M-l " 0.7 _ If M-l
- " "
= 0.7 = crf f ~. and now strength is 69,OOOlbflin2•.•
_ Failure Stress. 0', = 0.7 x 69,000 = 48,300 lbfli nl _ This failure stress is above my operating stress (30,000 lbflin 2) _ Therefore my throug hwall defec t leaks and does not ruptur e.
It
1 <0.) 1'.( k
'l71
"
.." .. .. f 0 _
_
_
••
J-tI.oooo.o J.: J
. ".
"
2c1(Rt)U (nonnOil lised defect lengt h)
" ~I
••
&<1
50
25
THROUGH WALL DEFECTS Example No.1: Calculation using Graph _ 36" diam eter, D (radius. R '" 18"),0.5" wall thickness (t), X60
"
_6 incillong;roughwall defect _ 2c/ Rt = 61 8xO.5'" 2 _ The operating press ure (P) is 834 psi ::: 30,000 Ibllin2 _ Operat ing st resslyield strength Is 0.5 _ Nole we put the operating stress along the y-axis , as are determining if this defect will fail at operation _ The point falls below the leak/ruptu re boundary _ Therefore this defect will no fail. it will ·only'leak .
-
• • • • • • • •~
we
RUPTURE (failure)
• ••
•• •• • I
LEAK (no failure)
•
• 2c1(Rt)AO.5
•
•
• 51
FAILURE OF A PART WALL DEFECT
C_llXIlI .... ....
sa
26
A PART WALL DEFECT part -w all defect
::
I
2.
•I )
d '
0_2001_..'
53
PART WALL DEFECT - Defect Dimensions
Maximum defect dept h, d
I (or 2c)
1
I
"I
=rr------r--II d = l (or2c ) =
t
III _
=
defect depth defect axial lenglh pipe wall thickness
2001 "'- ..,
27
PART WALL DEFECT - Defect Dimensions Defect area
1 ---:=~~ ~_~ =
d
---,I
defect depth defect axial length pipe wall th ickness
l(or 2c) =
=
t
I (or 2c)
55
PART WALL DEFECT - Failure Process
(~ . ~ .., i
.
_ _ 2006_611
56
28
PART WALL DEFECT - Failure Process . A part wall defect in a pipeline fails as follows: _ The defect 'bulges' as the pressure in the pipel ine is increased
_ A part-wall defect bulg es less than a through wa ll defect of the same length , because the m aterial in the rem aining ligam ent resists the internal pressure _ The ligament below the defect plastically deforms
. 'Stable' crac k growth starts. and the pressure continues to increa se _ If the pressure is stopped during this growth , the growth stops
. 'Unstable' crack growth. leading to a leak or a rupture
O_2lXJe_1I/1
PART WALL DEFECT - Background to Failure Equations
• They compared thei r pred icted failure stresses of pipeline sections containing part wall defects • T hey found a good correlation with the measu red fai lure stress. O_2\lllt_ ....
.
•
,
•
• •
•
•
•
•
••
• •
.--....
_
o __.... _
.. .
• They found that simple equati ons could describe the failure of defec ts in pipelines.
Predict&d Failure Stress ","",_(%1
~
• Th e early workers at Battelle conducte d many full scale tests
• 58
29
PART WALL DEFECTS - Failure Equations d 1- -
uf =
I
d 1 1- - -
1M
.
0<
= = = = = = =
a d
t A A, M
,d
"
"
- -- - - - - - - -
where
u,
ae
A A, ut = A 1
--
hoop stress al failure flow strength defect depth pipe wall thickness cross sectional area of metal loss original cross sec tional area The se equations apply Folias factor (bulging facto r)
to internal and external defects
O _ _ _ 1W1
59
FAIL NO FAIL
PART WALL DEFECTS - Failure Curves
Flow a trooQth • 1.15 " ,
.:::::::::::::::--------
~ d,....lt = 0.4 05 0."
0.7
08
0.' 0.95
a 0
..'
2c1(Rt)AO.5
•
•
•
30
PART WALL DEFECTS - Failure Curves
:;
,
'11." "rola
1.0_40(* r
••
2c
"
"'i«
I
~
FIow..nnglh.
1.1 ~
t
C
e ;;:) ot
AJA" '" 0.4
-e
:;;
0.'
~ o.
•e
o.
en o.
••
0.7
•2
0.e
~"
0.9 0.95
••
,
e_1OOlI_ .. '
•
•
A." a 2c.t
•
2c1(Rt )"O.5
PART WALL DEFECTS - Pressure/Stress used in Failure Equations
et
a/
a
d I- -
=
I
d 1 1- - 1M
_If you are calculating the FAILURE STRESS (or pressure) of a known defect in a pipeline, this predicted failure stress must be compa red to the maximum opera ting stress in your pipeline. _ If the predicted fai lure stress (or pressu re) of a defect max imum operating stress (or pres sure), the defect will _ If the predicted failu re stress (or pres sure) of a defect max imum operating stress (or pres sure ), the defect will pipeline .
is below the fail the pipe line . is above the not fail the
_Remember that the maximum operating stress in your pipeline may occasionally be above your MAOP and your design stress. _This maximum stress (pressure) may be governed by settings on relief valves, leak detection systems. etc., And this maximum stress (pressure) may be > design e_2llOe_ ....
62
31
d
I- -
PART WALL DEFECTS - Example using Failure Equations
Contains a part wall defect of depth (d) of 0 .25", and length (2c ) of
-a U a 20
'" '" " :: '"
failure stress flow strength defect depth '" 0.25 pipe wall thickness 6·
M
::
Folias factor (bulging faetor)
-
1-0.5,11-0.5(111 .61 ) 0.72x69.000
,
I
d 1 1- - 1M
6~.
Toughness (e v) '" 30ftlb
:60,OOOx1 .15
=69.OOOlbflIn2
d/l:"O.5 2c1(Rt)"O.5" 61/18xO.5Y'Q.5
.'-1-
1+0.4{ Ji;
r
"0.72 " 50 ,000 Iblliw
-2 "1 .61
= 83% SMYS
FAILURE STR ESS IS . 83% SMYS
~_:IOlll_ lIl
OJ
Is this 'Acceplable'
PART WALL DEFECTS - Example using Failure Curves 6" • ............
-"--
- '"
2e1(Rt)AD.5
._- ..
.
.-
-----
-'"
• 2cJ(Rt )" O.5
0 _ 2OOt _
,
0.6
.
.
........................................... .............................................._..
-' "
,
.
.
. ..................
"
d/t = 0.4
05
........-....
I calculate my ---.....
...............
0.7
.
08 0.9 0.95
•
..l
32
PART WALL DEFECTS - Leak/Rupture
••
I
I .
,
I
• 0
,.-
RUPTURE
t, '
.
••
•• ,•
I !. !
•
LEAK
•
•
I•
•
,
I.
•
•
•
•,
•
•
,
~ ·.~ • u,
• •
= ,U-'ij
,•
Battelle test data
O~2OOI _ lV'I
65
PART WALL DEFECTS - Failure and Leak/Rupture
" •
dfl
-=
EA~K~:::::::::::=--
= 0.4
05 0.6 0.7 0.8
,
• 2c1(Rt)"O.5 66
33
PART WALL DEFECTS - Leak/Rupture ' T h r e s h o l d'
or 'Boundary' _ As part wall defects increase in length. t. ' they are more likely to rup ture.
that curve is starting to 8 Wethe canleak seerupture from the figure opposite, plateau at a stress of about 30% SMYS . .Historically, this '30%' has been consider ed the leak/rupture thresh old or boundary:
I" J"I. ~~~!~~~~~~~'~I"'I.... O'
i
~ .,
-:
_ Defects of any size, at stresses below 30% SMYS will leak rathe r than rupture
_.
.. ..
••
• This boundary does not actually exist. and the long defects at this stress level would release significant amounts of product, equivalent to a rupture, although the defect would not propagate along the pipeline. a Recent work at Battetlle" indicates that the 30% SMYS threshold is reasonable for corrosion defects , but mechanical dam age defe cts m ay have a lower threshold (25% SMYS) 0 _ 2006 _ 61,
"
PART WALL DEFECTS - Summary
af a
=-
d I- -
I ---,-',1 d I 1- - 1M
Where (e.g.): M =
.. _
"2-
=
a
=
d 2c I R M
=
2OOI1Iow 11/'
=
= = =
• hoop stress at failure flow strength defect depth defect axial length pipe wall thickness pipe radius Fouasfactor (bulging factor)
_. ee
34
OTHER CONSIDERATIONS
0_2OOII_lI/l
69
CIRCUMFERENTIAL DEFECTS
part-w all de fec t
2,
zc d
t
o
defect longitudinal (axial) length defect depth pipe wall thicknes s pipe diameter
C_2OOlI_..,
35
INTERACTING DEFECTS pe rt-wan defects
defects are said to interact when the behaviour of the defects considered together differs to that of the defects when considered individuall y e_2OOlI_....
"
SAFETY FACTORS ON PIPELINE DESIGN PRESSURE ' Desig n Factor ' (hoo p stress/ SMYS)
"Ac tual failure stress of detect-tree p ipe is UTS Of > 1.25.S MYS
1.4 , - - - - - - - - - - -1-----, r=::-:':=~--;-:--, _ We MUST apply a safety factor to our defect calculations to accommodate:
1.2 1
e o vercressores (<10% of MAO P), _ Time depende nt effects « 5% of failure pressure). _ Mal erial variations (e.g. SMYS aod w.l.) , e u nceternees in defect equation ,
0.8 0.8
0.4 0.2
e u ncerteo ues in defect measurements,
o _ _ 2005_&11
_ Etc.
Design _
..... '
__
Hydrotest
~_~
R
Failure .-o." _
-'OO
_
12
36
SAFETY FACTORS IN PIPELINE DEFECT ASSESSMENT • Because of uncertainty in defect measurements, operational parameters, material properties. etc., it is usual to apply a safety factor to defect failure calculations. • Th is safety factor is generally (e.g. ASM E B31G) taken as 1.39 • This means that if (e.g.) your failure pressures is 139 bar, the 'safe ' pressure would be 100 bar. • This assumes NO FURTHER GROWTH OF THE DEFECT IN QUESTION . •
If your defect is growing. you must establish the final (end of growth) defect size. and use this final size in your failure calculations.
0_2OOlI_."
OTHER TYPES OF PIPELINE DEFECT ASSESSMENT D AT A
STA( a :s
0_20010 .......
37
- - - - - - - - - - - - - - - - -- -
ADDITIONAL INFORMATION
BACKGROUND TO METHODS FOR ASSESSING METAL LOSS DEFECTS - TOUGHNESS DEPENDENT
,.
cw
"c
ill
"
Q
W
~ li:1 "
~L "
OJ ,, • I o~ ;
.\f",
• TOUGHNESS OEP(NOENT
; "
" " " "
. ." C _~ :1OOll R . v 6l '
K,l;r
&'0'"1
C
t Mal
.!2 EJr
'&'AO" ~
«
-
FLOW STRE NGTH DEf'ENOENT wjt
28
In scc
,
Y
0"0 °:
., • ,
. .•• . • ..•• • • • • ... .. . , .. I.
M - a'
•
.~.': .
'
•
• to"""'h .... ....""
,
C. I
",'
,
110 '::'
".'n
Li ne pipe with lower toughness ta iled with little deformation , and these failures we re described by this
I \~oughn ess dependent (Cv)
~
..
,
re lalionsh;p . Tho se that failed with large deformation were de scribed by the flo w strength (tens ile properties)
I dependent relationship.
-
76
38
BACKGROUND TO METHODS FOR ASSESSING METAL LOSS DEFECTS - TOUGHNESS DEPENDENT MtT.'"
U,'"
• •
..
• 0
" _ _ II
0
•
.. ~i
0
-
' 0 0
~.-
•Tloey... .-, I• o.
• "t •- •
,• , •
,-.. - Ij .. ~
<>8 .
0
. ."
'0•••
•
0
•"
•
(~l
C._ E_
....:t"r-.~ ~
0
•
:.0 '
'Ln sec' equation is close to a lower bound for part wall defect tests
--
o •••
._-
0
0 __
['-~-:'II
," --:-T" , .;
LL
O~
.L
0
O_2O»_vt
•
--_.... •
-"-
-'-
•
..' 11
c,-;{E.
-'
tn sec ' equation s a 'good' fit to wall feet tests
"
'0
77
BACKGROUND TO METHODS FOR ASSESSING METAL LOSS DEFECTS - Cv versus K
.. G=K' /E
Note: We usually take our Charpy specimen from the transverse direction of the line pipe, well away from the weld, and as we do not 'natten ' our Charpy, it usua lly is 'subsize' (less than 10K10mm cross section) due to the thin wall pipe
•
•
• •.'
.
•
•
_-
• roo _ _
. .. •
.:te./A • •• • - .
.
-
re
39
SMYS, SMTS and the FLOW STRENGTH
,.
, ", •
,.
-
I •• l• , •
;
-
->:
•,; ,. >
•• ,.
I ~'
,.
,~,
,. e Cl~ 200lIR.., $'1
'"
."
'"
.~
,-
.00
•cv
0 0
..,
._, , 'oSUYS
$.\1>"$....'" ,, ~
IS...5.5....,5)'2
".
. 00
zs
40
How to Assess Corrosion Defects Penspen Integrity
O Pe n....... 2"'" Rev
1
LECTURE
• •
Introduction
Axial corrosion defect assessment
•
Circumferential corrosion defect assessment
•
Published methodo logies for assessing corros ion
•
Summary of published methods
•
•
• AS ME 831G
• Modified 831 G
. DNV
•
Other cons iderations
•
Constructing acceptance charts
2
INTRODUCTION
3
INTRODUCTION: What is Corrosion? •
Corrosion is a time dependent, env ironme ntally-assisted me chan ism that causes a metal to deteriorate by reaction with its environment.
•
Corros ion results in: • metal loss .
• The co rrosion defect can have a smooth or irregular profile. and possibly contai n blunt or sharp features . • sometimes cracking.
,
2
INTRODUCTION: What Causes Corrosion? •
Co rros ion req uires four factors to be present: • anode ;
• cathode; • metallic path connecting the anode and cathode (e .q. a pipeline); • an electrolyte (e.q. soil and groundwater for external pipewall corrosion. or untreated crude oil for internal pipewall corrosion).
---_.......-
• If any of these facto rs are not present or prevented (e.g. coaling a pipeline ), then corrosion can not occur.
5
INTRODUCTION: Major Causes of Corrosion •
Corros ion can be caused by ga lvan ic attack, or it may be chem ically induced (e.g. microbiologica l induced co rros ion) . • Ga lvanic co rros ion is associated with the flow of cu rrent between" two metals (one an anode, the othe r a cathode) in a com mon electrolyte
• Most metals contain both anodic and cathodic areas (e .g. old pipe connected to new pipe), e n can result in large areas of gene ral corrosion, local pitting, and/or selective corrosion .
-"""'--_....
6
3
INTRODUCTION : Major Causes of Corrosion •
Corrosion can be caused by galvanic attac k, or it may be chemi cally induced (e.q . mic robiologica l induced co rros ion) . • Microbiol ogica l Induced Corros ion (M IG) is from bacteria that is alwa ys present in soil. wate r, etc .. • The bacteria do not cause the corrosion - but the y create changes in the electrolyte, e.g. by changing sulphides into sulphuric acid. • MIC typica lly has a rougher surface with axia lly orientated ridges.
MIC .. ..-go.
......
s_...._ . _
~ , wwwolllloul
0 _ 200ll
Rov5I'
7
INTRODUCTION: Corrosion Types •
We can have corrosion in a variety of locations: • Internal (pipewall) corrosion • External (pipewall) corrosion • Corrosion in the pa rent plate • Co rrosion approachinglinlcrossing girth!
seam welds. •
It can be in differing orient ations: • Axia l • Circumferential • Spiral
•
• Random It can result in.. . • a single corrosion defects • colonies of interacting corrosion defects 8
4
INTRODUCTION: Corrosion Types
9
INTRODUCTION: Preferential Corrosion at ERW Welds •
Electric resistance (ERW )* or flash welded (FW) seam weld s are susceptible to 'preferential' corrosion.
•
The bond line co rrodes preferentially to the surroundi ng steel. It can produce a 'sharp' Vshaped notch along the bondline (external and interna l surfaces can be corroded) . • Note that this is predominantly a problem with older ERW and FW line pipe .
--_ .. __ .. _----_._-_.-_ _--_-_.. _---. . .. -_._--. _-_......._--_ ..--- --~-_.-
5
INTRODUCTION: Preferential Corrosion at Welds • Preferential corrosion can occur at welds (girth and seam ). • 'Narrow axial external corrosion' can occur along longi tud inal weld s in wrapped pipe
• Cauti on is requi red when asse ssing corrosion in low toughness wel~~ s~o:r corrosion coincident with weld defects.
i~~~i:::J
0_:10:16_
11
INTRODUCTION: Environmental Cracking (HIC, SCC and SSCC) •
•
Environmentally assisted corrosion , suc h as stress corrosion crac king (low pH and hig h pH Sec). hydrogen induced crac king (HIC), etc. , mu st be asse ssed using a differing me th od olog y to that described subs equently, becau se the de gradation mechanism causes cracking, bli stering, et c..
~=.., . t ) '
l
I
Hie . sec. SSCC are cov ered in the 'How to Assess Cracks' part of the course. • They are usua lly controlled or prevented by materia l se lection , con trol of product , etc ., and their act ual assessment is rare.
...
"""-.-.....
"'~"'
"0.-. _
" • .J . • •. e . - _
"
6
.. ...... . f.
Very old. low toughness line pipe & welds are not cov ered by our equations.
Ch¥py fFvI,...,
.~.....
R'
.,
0 ••
• 1.3
Scatter 0.8
'Toughness' Dependent
'Flow Stress' Dependent (Using flow stress = (yield + UTS)/2)
i
-27J (Full Size Charpy) (20 fl lb)
o
Toughne ss 13
•
Charpy (f'~ s-,o ..
R'
..
INTRODUCTION: Effect of Toughness Examp le of 'old' line pip e toughne ss in USA
II
" , - - - - - - - - ----::--::------:,........, !f"---.>.--- -e
."",
, ,
_ _ iOVCfa9" impac! energy
-Go- ·avemge she..........
"• • I II 1;
i
;
•
J
u
~
t
.
~ ,,
10
.. SO
,~
30
8
C = - 7ft Jb or.- 9 J
•
, e
0 _ 2OOlI _ _
.,"
r
1.
----"" .. -.....-.---_ _ . _ .-, ~
',, _.-
.....
_-~
...
'"
••
-
,.
Grade
..
. -!
,r
~ 18
..
' 00
so
t
. . 18
..
I
~
f
" "
'"
_------,-
"
7
INTRODUCTION - Definition of Corrosion D imensions d = 2c(orf) = 2c' (or l J = t = D =
defect deplh
defect axiallenglh circumferenliallen gth pipe wall thickne ss pipe diame ter
longitudinal extent
circum ferential extent 2,
I-
2(:
.:
C
J!
••
d
"ce .!
,E l::!
U
l o ng itud inal extent
AXIAL CORROSION DEFECT ASSESSMENT
._--
16
8
CORROSION DEFECT - Axial Dimensions
~
.
I. •
2,
.1
; S;;;.A 02 d
1
2c (Of I)
f
TF--",--~ -------",-----II d = 2c(orl) = t =
defect depth defect axial length pipe wall thickness 17
AXIAL CORROSION DEFECTS· History of Assessment Methods •
•
The methods for assessing corros ion defects are based on research at Battelle Memorial Institute (USA) in the 19605 & 70s , for the American Gas As sociation (AGA) . Up to 1973, over 300 full sca le tests were completed, including: • 92 tests on arti ficia llhrough wa ll defects. • 48 tests on arti ficial part wal l defects (machined V-shaped notches).
•
They developed: • a failure criterion for through wa ll defects . • a fa ilure criterion for part wall defects.
•
Subsequently, mo re tests, and num erical analysis, have been used to further validate , and deve lop methods for assessing co rrosion.
~~
~
9
AXIAL CORROSION DEFECTS - Failure of 'blunt' defects •
A blunt defect such as co rrosion can fail in two ways in line pipe (excluding cleavage failure)": •
A s the load (pressure) inc reases, loca l wall thinning will occur in the remaining net section, This loca l wall thinn ing could continue , lead ing to necking of the wall and
failure due to void nucleation, grO'Mh and coalescence. similar to a tensile lest specimen, and hence failure is do mi nated by the ultimate ten sile strength (plastic collap se )• •
A crack coul d init iate at the base of the defect due to the presence of micro-stre ss raisers (e.g . local su rface irregularities caused by a corr osion mechanism ) th roogh a process of void nucleation and growth .
• The behaviou r al'\et!he initiation of II c:rad< would depend on !he IQughness of the matenal: • In II high toughness malena l, m alion would be deIa~ to a higher load and fumstable duetile tearing would be sJov,er. or a g..,..,;ng c:rad< oould blunt; wal l lt1inning would CQIlbnue and the lailure load would tend to that of plasbc co/Iapse .
• In a Iowef tough ness matenal. once initi aled. the crack would e~ end by stable ductile tearing, reduci ng the rema ining wa lilhick ness and hence reducing \he degree of wall thinni ng that occurs before failure. • The load at failure wou ld be less than that predicted by the plast ic col lapse hmit state becau se of the stable duct ile tearing
_ ___.._ _..._ . _l>->O ~, ._ ·.......... '..._ ___.._ ..-..,..._ ·.... ' _ -.. .. ""'.......... ...-1'-1
.....,_..· ... _ .._ ........__ ......._ •, ___ _ _.._ ___
·.. _-........_ ,·tItl
l>->O ~ ' .'
19
AXIAL CORROSION DEFECTS - Failure Equations
d
A
I
Ao A 1
d 1 1 - - -1M
'"
a d
t
A A, M
= = = = = = =
1- -
•
-
Ao M
(In terms of defect area ) hoop stress at failur e flow stress These equations apply defect depth to internal and external pipe wall thickness defects cross sectiona l area of metal loss original cross sectional area Folias factor (bulging facto r) These equations are known as the 'NG18' equations, after the project number used to deveiop the equations at Battelie
01'...-2005_ '
20
10
d 1- -
,
AXIAL CORROSION DEFECTS -
d 1 1- - t M
Folias/'Bulging' Factor
..
. ••
--..",
..
' oog
"""",
. M-' . . . . . . . . .. .. .. LEAK
e xtensively.
....'"""'''''''''
.... --
A$ buIgiI'Ig
RUPTURE
,
__u, ""'"
2,
.
.
••
••
••
2c1JRt (normalised defec t length ) 21
d 1- -
,
AXIAL CORROSION DEFECTS· Failure Curves·
d 1 1- - I AI
" EA:L
o FAIL
:::::::::::::=-------------1
dlt · 0.4 0.5 0 .6 0.7 0.8
0'
,
,
•
•
2c1JRt (nonmalised defect length)
0 95
_..._ -,---
,
22
11
AXIAL CORROSION DEFECTS· The curves are applicable to both internal & external defects d
I- -
I
d I 1- - -
1M
~.
1
TEl
ItH ERNAL CORROSION
..
~
i
IT 1, <"
IT 23
CORROSION DEFECTS - Why Don't Pits Fail?
Radial stress is small Defect does not want to fail 'outwa rds'
"./ /"
Small defect cannot move to fail. It is restrained by the elastic mass surroundin "I
O_200S_1II1
24
12
AXIAL CORROSION DEFECTS " " - Leak/Rupture "
"
d/l .. 0.4
.5
.,
RUPTU
'.6
2
3
5.
2c/JRt (normalised defect length) D_2ODIl_l ~Il"""'''''
.... __..
~
..._l_ _
•
-----,--
25
GRI_~_lOO2
AXIAL CORROSION DEFECTS - More Likely to Fail as a Leak
e c orroston is a time dependent failure. _It can preferentially cor rode to a leak , even when its length is sufficient to cause rupture - So, corrosion 'prefers' to leak, but corrosion CAN AND DOES rupture
Overall length should cause rupture Very deep area in pit corrodes to a pinhole and leaks O~2OOI_
26
13
AXIAL CORROSION DEFECTS· Pressure/Stress to use in Equations _I f you are calculating the FAILURE STRESS (or pressure ) of a known defect in a pipeline, this predicted failure stress must be compared to the maximum operating stress in your pipeline. I d _ If the pred icted failure stress (or pressure) of a defect is a I - below the maximum operatiny ' _ 1_ = t stress (or press ure) , the defect I ~ = ~_ ~ __1_ will fail the pipeline. ~ t M _I f the pred icted failure stress (or pressure) of a defect is above the maximum operating stress (or pressure ), the defect will not fail the pipeline .
"'-J
AXIAL CORROSION DEFECTS· Pressure/Stress to use in Equations _I f you are calculating the DEFECT SIZE that will fail at the op erating (hoop ) stress of the pipelin; , the operating stress is cc:.:t:.: h:= e-=e:..:q'7u=i!ll( i:= o:.: ns"'.' ---,-,-, used as the failure stress in _ Remember that the r maximum operating 1CY a operating pressu re (stress) in your I = - f = - ----;-'--;-pipeline may occasionally d 1 CY
/
be above your design
~
1- - - 1M
pressure (stress). _This maximum stress (and hence maximum internal pressure) may be gove rned by settings on relief valves, leak detection systems, etc., and this maximum stress (pressure) may be higher than the design stress (pressure). e>_:lOOI-.
28
14
CORROSION DEFECT: Not axially-orientated (but m a in dimension is axial), internal pressure loads
Corrosion can be 'non-axial': de pth/area is the same, but length needs to be 'projected' to give an equiva lent length. Use this equivalent length in equations.
Equivalent axial length For defects not aligned with the longitudinal axis, projec ting the defecllength onlo the longitudi nal axis will be conservative .
29
CIRCUMFERENTIAL CORROSION DEFECT ASSESSMENT
15
CIRCUMFERENTIAL CORROSION DEFECT· Loads
In t ern al
pr essure
•
Internal pressu re induces a hoop stress and an axia l stress . The hoop stress is at least twice the axi al stress, depending on the end restraint.
•
Thermal loads, g round or pipe movement, loss of support (e.g. span ning ), bends, supports. etc., can induce axial and/or bending stresses.
at
CORROSION DEFECTS IN CIRCUMFERENTIAL DIRECTION _ AX IAL stress, NO T hoop stress may be the major stress acting on defect. e o nen you must check for failure due to both hoop stress & axi al stress . _Axial stress is from interna l pressure, thermal stresses, grou nd movements ,
etc..
longitudin al length failure ceterce for longitudinal extent uses internal pressu re 32
16
CIRCUMFERENTIAL CORROSION DEFECT: Background To 'Kastner et al.'
•
Kastner et at pubflsned a failure criterion for a single, circumfe rential part-wa ll defect subject to internal pressu re, ax ial and/or bend ing loads. •
•
This is now the most popular method for assessing circumferential corrosion
Th e failure criterion was deve loped for interna l pressu re loading only, but has been shown to be app licable to any axial load by replacing the ax ial stress due to internal pressure with the tota ! axial stress.
•
The theoretical model was compared with the results of tests of part-wall notches, slots or cracks under internal pressure, and internal pressure and inplane bending .
'--"---"--,--- _ . ~ ,
-.-'
- - _ . _ ~ - ~. ~ -
33
CIRCUMFERENTIAL CORROSION DEFECT: Kastner et al. Equation ze
lJ(;r - ,8[I -lJ]) rpt + 2[I - lJ] sin (,8 )
,8 =~
R
"!.
or
d 2c
t R
= = = = = =
d
1] = 1- -
t axial stress at failure flow stress defect depth circumferenliallength of defect pipe wa ll th ickness pipe radius
17
CIRCUMFERENTIAL CORROSION DEFECT: Typical Use o f Kastner at al Equation ' .0
~f
09
iY =
I! 0.8
"(' -/1(1 -")) "H 2(1 ")'in(p)
a
: 0.7
Cin:u~~enl'"
•
<
~ 0.6
"a
' i 0.5
~
UNACCEP TABLE
0
0.4
• .i" 0.3 • 0.2
()
/
/
Kastner et al. (X42)
/
Kastner e tal. (X65)
-.;I
0' 0.0
ACCEPTABLE
L.-~~~~~~~~~~~~~~_~~--J
0 ,0 0.2 0 ,4 0.6 0,8 1.0 1,2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 30 3.2 nor malis ed de fect cl rcumfere nl iallangth (c/RI
35
WHEN DOES THE CIRCUMFERENTIAL EXTENT OF A CORROSION DEFECT NEED TO BE CONSIDERED? _ Corrosion can have ax ial extent and circumferent ial exte nt a r heretore. it can fail due to hoop stress and axial stress
a u nder pressure loading only, the axial dimension is the critical dimension, and unless the circumferential length > axial length , you need not consider the circumferential failure . _ If you have extema lloads (e.g. mining subs idence or spanni ng ) you mu st co nduct the two ca lculations: _ Failure unde r pressu re loading _ Fa ilure due 10 the axial loads
Hoop Stre ss from press ure loading
36
18
PUBLISHED 'METHODOLOGIES' FOR ASSESSING CORROSION DEFECTS
o_~_
CORROSION ASSESSMENT METHODS _The equations we have covered (e .g. the 'NG 18' equations) are 'classic' or historical equat ions . aThey are very good!
_But we have to choose a flow strength, Fcltas factor, safety facto r, etc.. _This may be difficu lt. .Plus, they do not tell you if a specific defe ct is 'acceptable'. _Therefore , organisations have produ ced guidance documents that present a complete procedu re for assessing corrosio n. e 'rt ese methods are used exten sively for assess ing co rros ion dala reported by pigs .
0_2001_
38
19
PUBLISHED METHODS FOR ASSESSING CORROSION •
'O LD' METHOD S
•• •
ANSI/ASME B31G modified 8 31G RSTRENGTM(Remaining Stren g th of Corroded Pi pe)
•
'N EW' METH ODS
• •
•
SHELL 92 Line pipe Corrosion Group Sponsored Project (LCG SP) [DNV-RPF10 1) DNV Joint Industry Proj ect (DNV·RP·F101]
• •
PCORR PCORRC
•
Pipe Ax ial Flaw Failure Criterion (PAF FC)
•
API 579
:~~~~b:ll
39
'OL D' AND ' N EW ' PUBLISHED METHODS • The 'old ' methods for predicting the burst press ure of a corroded pipeline methods) were , predom inantly, deve loped & validated through full sca le tests on older line pipe steels. • these methods are biased towards older. relatively lower toughness. steel • these methods are gene rally applicable to older, dirtier steels and should be used whenever there is a doubt rega rding the applicability of the 'new' methods.
0_
OL
• The 'new' methods were developed and validated through tests on modern , high toughness, line pipe steels . • These m ethods are bia sed towards the behaviour of modern , high toughness, line pipe stee ls. 2OOlI_611
20
' OL D' AND ' NEW' PUBLISHED METHODS • The 'new' methods should not be considered if any of the following apply: • the:y, thickness speci m en size upper shelf Charpy V-not ch impact energy is tess than 18 J (13 ftlbf» (the full size equivalent is 27 J*). or • the minim um elon gation req uirements in API 5L are not satisfi ed, or
jJ.~ I
• line pipe steels suspected of containing a significant number of inclusions, second phase particles. or othe r conta minants (i.e. 'dirty' steels); • typically this will exclude lower grade line pipe (grades A and B) and some older vintage line pipe.
0_2OOI!_1 "SM
._~lfl,oIl'al "' VJ_"'~'-"""Y
_ _ " ' _ " ' ' ' ' _ _ ''''''
41
MAJOR PUBLISHED METHODS FOR ASSESSING CORROSION •
We will now concentrate on ASME 831 G, mod ified B31G, and DNV-RP-F101
• All these methods assume: • the corrosion defect is blunt, Le. it contains no sharp,
(
)i BLUNT~
• the failu re of a corrosion defect is assumed to be due to plastic co llapse (i.e . co ntrolle d by the tensile properties of the line pipe steel).
~
) CO. LAPS E'
• the fa ilure is under inlem al pressu re loading. • Only DNV RP-F101 considers the effects of other loads.
~
J RES SURE'
cra ck-like featu res.
•
The me thod s differ in certain of the assumption s and simp lificatio ns made in their deri vation : • defect profile • flow stress • geome try (bulging) correction fact or (' Folias' factor)
-
0","- _ _
21
IDEALISATIONS OF A CORROSION DEFECT PROFILE
43
IDEALISATIONS OF A CORROSION DEFECT PROFILE - ACTUAL AREA
.-or--" '- - - - - - - - - - - - -------,,,
"m~l,
'l~
-'-' - - - - -- - - - - - - - - - - - -- - ---' A
"_2OOlI_'
22
IDEALISATIONS OF A CORROSION DEFECT PROFILE - RECTANGULAR PROFILE
, ,
-r-r-r-
,
m~
,
tot,,1
I'
1
H~
t:
/ _
_
_
_ _
_
_
__
~
_.ori
"'*
~"'''''' ._
* _____
* ~ .l:
--'--
~ = ltuta,dmax =
A,
«:
d m
t
CPo_20CJ6R",,6I1
45
IDEALISATIONS OF A CORROSION DEFECT PROFILE · PARABOLIC PROFILE
• I
row 1
"m~U~ --'--'-- - -- - - - - - -- - - - - -- -- --' ~ = ~ d m{u 'lOlal Ao 3 / /(>1<111 o poo""", 2OCJ6
"0'1611
=
2d 3t 46
23
COMPARISON OF RECTANGULAR AND PARABOLIC PROFILE
.
'
.
I
,
~ m~
,
.
I
i~ ~
-
-
-
-
-
I
."
I
/
/.-/
-
-
--
:.---
-----
,,;
,, , - .,
--'-
0_ 2OOli _
"
ASME B31G
"
24
ASME B31G: The Background •
•
-_ . __ ... _--
"'="'.
In the 19805 the pipeline industry identified a need for sta ndardised gu ide lines for the assessment of corrosion in pipelines.
...
ASME producecl ASME 831 G for the
assessmentof corrosion defects •
ASME used Ihe Battelle" work on corrosion
Manu al f or Det erm ining
•
It is applicable to corrosion in Ihe body of line pipe whic h have relatively smooth co ntou rs and cause low stres s
t he Re maining St rength of Co rrode d Pipelin e,
concentration (e.g. electrolytic or galvanic corrosion , loss of wall thickness due to erosion). •
~ _
. _n,_
~ --
It is not app lica ble to corroded girt h or longitudinal welds or rela ted heat affected zones .
C_2OOI_ -.- ._~
<
,,,
-
as
\\ ASME B31 G: The Assumptions
I •
Validated on 47 full scale tests containing actual corrosion
Major Assum ptio ns/lim its in AS ME B31G* : 80%
• Maxim um allow able depth is 80 perce nt of nom inal wall thickness.
~
• Ass umes a flow stress equal to 1.1 x SMYS • 'Two term ' Fettes factor. • Assumes a parabolic defect shape for short corros ion (defined as M :s; 4 .12), and a re ctangular shape for long co rrosion (for long co rrosion the parabolic shape assumption becomes invalid). • Acceptable defect size calculated for a stre ss level of 100% SMYS . • _ _ ... _ _ _
"",,0 375
__ _""
_ASUlE I31G·. (,2
T... _ _ ..
oo
_
~
.
J O"' _
l _ ASUEBJ 'Gl
50
25
ASME B31G: The Equations
(J
= l.l x SMYS
a,
=
o
=
d 2c
=
t
= =
M
=
o
M=
l+O{hrJ
hoop stress at failure flow stre ss corrosion defect depth corrosion defect axia l leng th pipe wall thickness pipe diam eter Fo nes factor (bulging factor)
=
AS ME 8 31G is now widely accepted in other standards. e .g.
AS 2885 .3
51
ASME B31G: The Graph 1.0
0.9
80%
-~
8 5°. =
~ 0.7
~ 0.6
':i
$ 5
~
o
0.5 0.4
t; 0.3
e
TolManc"'~'. " 'PA SS' ~~~~ ~-_ ~
o 0
_
100% SMYS 'failure' line
A CCEPTAB';;L~E------<
~ 0.2
01 00
UNACCEPTA BLE 'FAIL'
2
3
~
,
2c1JRt
5
6
'------I _ - --1
_
7
•
L - - - - - - -, De w...."'ITen gth PaO;,.;;m;;;.;;; 1e ;;'- - - - - - - ---' 52
26
ASME B31G: An Example
~
09
~
~
0 .8
U
:E
I-
0 .7
----------:
- - - --- --_ . ,_ •••••••• j •••••••••
<".
... •. ••.••••••• ~
..........• ........
--------- j--- -------:-
-l-
+ + . "j ··········r········":
--------, - --- -- --- ------ ---- . --
. ......::•......... ··········1··········, ·······T········ -- --- -- -- - - -- -- -----
-.".
," '00
Corrosion Length (mm) 53
27
'ESTIMATED REPAIR FACTOR' • • • •
It::- J
An intelligent pig inspection report will sometimes refer to the ERF (esti mated repair factor) of a defect. The ERF ca lculation is another way of ex pressing an ASM E B31G assessment. If the ERF is less than one the defect is acceptable to AS ME 8 31G. If the ERF is greater than one the defect is not acce ptable to ASME
8 31G.
ERF = MAOP P' for
8$ 4.0
f' =
nollhe failure
"""""'" s= LlJf--Ql " ~T I
for 8> 4.0 0
P'i3 the safu opMWng PfflS!iUre.
P is the design pressure P' is the safe operating pressure
_
55
MODIFIED B31G
se
28
MODIFIED B31G - Background • Th e orig ina l B31 G criterion has been modified to reduce the perceived conservatism in the model. The modified criterion is referred to as modified B31G. T he criterion is incorporated into 'RST RENGTM',
f
Validated on 86 full scale tests with actual corrosion defects
• Maximum allowable depth is 80% of nom inal wall thickness. • Assumes a flow stress equal to SMYS + 10 'ksi' (68 .95 Nmm·2 ). • T hree term Folias factor. • As sumes an arbitrary area O~dorpl1I ..... ........ approximation, ItfM dIJ¢! corresponding to a factor of 0.85 , 'kosi'" 1OOO}( Ibf/in2 " 6.9N1mm'J 2ooe_'
,.
0_
1Oks;" 10,000 Ibflin2
MODIFIED B31 G - The Equations
a/=1 1-08~~l ]
(J
'k,i' '10k al'
= SAfYS + IOksi
1-0.85- -
' 1 0 k. 1'
t M
At =
I+O,627{k )' -O.00337\ k )'
for
The series solution is unstable at high values of
M =O.03~$r +33 1:7,
=
u
"
d I
=
t
= =
o
=
M
=
1000 Ibllin 2 " 1 0, OOOlbfl ln 2
It
.. 69Nlmm 2
C7>iy !>50.0
(*')
1
therefore:
for ( / )' > 50.0
lDi
hoop stress at failure flow stress corrosion defect depth corrosion defect axial length pipe wall thickness pipe diameter Fones factor (bulging factor)
58
29
MODIFIED 831 G - The Graphs
af
j
1 1 -0'85~ d I I
0: (7'
1-0.85- -
1M
1.0 0.9 :: 08
• ~ "
0]
a l-
.
~ modified B31G (X42)
0.6
modified B31G (X65)
~ 0.5 <
~ 04
C
a e
0.3
8 02 01
I
ASMEB31G /
0.0 0
1
2
J
4
5
r
6
2clJRt e_
6
fin-
2OOlI_611
59
MODIFIED 831 G - 'RSTRENGTM' • The modified B31G criterion is incorporated into co mmercial software called 'RSTRENGTM'. • RS T RENG ™ (Remaining Strength of Corrode d Pipe ) wa s
n
~
deve loped to allow the assessment of a 'river bottom pro file' of the co rroded area • This means you can use actual defect shape in RSTRENGTM and not use the '0 .85' factor
I
'-
I
I ~I
• It gives more accu rate pr ediction s tha n the sim ple modified B31G criterion. • RSTRENGTM do es both a modi fied 8 3 1G and a 'river bottom' calculation. • RST RENGTMdoes ot he r ca lculations (see later) 0_2006 _1
60
30
DNV RP-F101
C
p"""""" 200Il " ov6l1
61
DNV RP-F101 - Background • Based on the results of the Line pipe Corrosion Group Sponsored Project (BG) and a DNV Joint Industry Project. • Guidance produced for the assessment of: • single defects • interacting defects • complex shaped defects (i.e. assessing
the actual profile of the defect) • combined loading
• The BG and DNV work was co mbined to produce DNV RP-F101 62
31
DNV RP·F101 • Background BG Work •
Ex tensive re search programme by BG :
t •
>70 f ull sca le t ests on defects, and >over 400 numerical analyses (co m pu ter mod el s of defect s)
Guidance produced for the assessment of: • • •
•
single defects inte racting defects comple x shaped defects (i.e. assessing the actual profile of the defect)
The equation for assessing a single corros ion defect has the same basic form as the Battelle part wall failure criterion, • but the geometry corr ection factor has been modified (based on the resu lts of the numerica l analysis).
•
Th e flow stress is defined by the ultimate tensi le strength of the line pipe steel • with an adjustment of xO.9 · recomm ended to give lower bo und failu re oredicuons. 63
DNV Rp·F101 • Background DNV Work •
DNV Work:
, " •
12 full scale tests, pressure & other loads _ Numerical analyses (computer models of defects)
Guida nce produced for the assessment of: • •
sill9le defects combined loading
•
Not proven on Grade B or below, or low toughness line pipe
•
The DNV equ ations ass ume 'plastic coll apse' failu re.
""'oro
•
Modem liM pipe should fail by 'plastic collapse'
•
'Plastic collapse' can be expect ed when a minimum toughness is achieved
•
This has been estim ated: • by aartese' as a fun size Charpy 0160 10 75 ft.lbf (82 10 .. . • a ~ Charpy value of 45 ft-lbs (about 60 J)"
...... ,.. , _ .,"'
C _ ~ =l" _. _ . J
"_"""'
' - _ ___.
Check toughness
applying DNV
102 J ). which is simila r
._.. __'.
""",....... _e-;.-o ,..
_
64
32
ONV RP·F101 • The Equations 1- " r =O .9UTS
=
P,
a, d I
t 0 Q
UTS
O_2lM _ '
= = = = = = =
d]
[ I- f~
P = O. 9 2IUTS [ 1-
(D - I) I _~-'I Q
r
failure pressure failure stress corrosion defect depth corrosion defect axial length pipe wall thickness pipe diameter lengthcorrection rector ultimate tensile strength
7]
Note: The DNV methods have not been proven on older line pipe steels , and line pipe steel with low toughness «60J) . es
I --
ONV RP·F101 - The Graphs 1.0
'T'"- -
0.9
j:=i;"
:: 0.8
• ..i
•
0.7
I-
0.6
~
0.5
.. <
•g.
o r
»
O.9UTS
[
1-
d]
~t~
~~~----__,
•
DNV (X42) DNV (X65) modified 8 31 G (X42)
modified B31G (X65)
0.4
C
j
0.3
~ 0,2
0. 1
ASMEB31G / 2
3
,
5
6
7
6
2cllRt 66
33
DNV RP-F101 - Comparison wi th other Published Methods 1.0 ,..--
-
-
-
-
- - - - - - - - - --
0.9
-
---,
DNV (X42)
: 0.8
•o
DNV (X65)
~ 0.7
~ 0.6
pseudo modified 831G ( X42 )
i
0.5
pseudo modified B31G (X65)
j
0.3
•
5 ~ 0.4 c ~ 02
0.1 00
'-_~
o
~
2
3
~
4
5
_
6
_
-------' B
7
2t1(R1)"O .5
0_2005-.
67
DNV RP-F101 - The Equations
6 [
= 0 9 UTS
Q= P, C;
d I
= = = =
=
Q
=
=
t
1- d
p = 0 9 21UTS
[
I +O.{j~J
I
o
[1 ~1~]
fai lure pressure fai lure stress corrosion defect depth corrosion defect axial length pipe wa ll thickness pipe diameter length correction factor
·(D-/ )l_d J... [ I Q
]
-
Spreadsheets?
._--..".
68
34
SUMMARY OF METHODS FOR ASSESSING CORROSI O N
C Pon..- 2006 Row6l1
69
SUMMARY OF METHODS FOR ASSESSING CORROSION method
Batte lle
'fl o w
stress'
'NG-18'
l7y +
10 ksi
• rectangular (dlt) or
I
J"'HM IJ I+om{*r-ooom{*r
1.1SMY$
parabolic 2/3(dlt)
modified 831G
NG-18
SMYS +10 ksi
arbitrary O.85(dft)
RSTRENG
NG-18
SMYS +10
effective area and
ksi
effective length
O.9SMTS
rectangular (dft)
2006 """5i '
Jl.OM{ 1f:r -ooom{j&-r
defect area (AIA o ) NG-18
NG·18
'bulging' factor
defect shape
ASME B31G
DN V·RPF101
C P_
basic equation
Exact area
I ~l ' 0 627{~r
-o.oom{Tri)'
J'·'{zl' rc
35
SUMMARY OF METHODS FOR ASSESSING CORROSION d
1- -
1
d 1 1- - t
_.
AI
"
.,
ACCfl'T'~---'
ASMEB31G
"
I:
------I:
-
... , , , . . . , I" Mod ASME B31G
" ."!. --:--,--,-,--,----:-~
DNV
"
ASSESSI NG CORROSION - Further Considerations
•
72
36
ASSESSING CORROSION - Further Considerations
•
•
Using the actual defect shape in calculations Assessing a colony of interacting defects
0_2006_1
73
ASSESSING CORROSION - Further Considerations
37
USING THE ACTUAL SHAPE OF A CORROSION DEFECT IN ASSESSMENT METHODS • Exact area method
• RSTRENGTM • DNV RP- F101 • (Finite Element Analys is)
.....-
0_2OIl6-.
75
USING THE ACTUAL SHAPE OF A CORROSION DEFECT - Exact Area Method
A I - A o-
c
-~;"~-:P~.-
A 1 1- - A rl A1
~,,",- ~!"Al
76
38
USING THE ACTUAL SHAPE OF A CORROSION DEFECT - 'RSTRENGTM' •
•
W hen the mod ified B31G criterion was dev eloped, a method for assessing the actual shape of real corrosion defects was also ~ developed, based on the effective area method . The effective area method and the sim ple modified B31G method are incorporated into software referred to as RSTRENGT . .-
•
For simple hand ca lculations a geo metric shape approximation is reco mmended (this method is ofte n referred to as modified B31G), in which the defect area is assumed to be O.85dL.
•
The RSTR ENGTIoI method is used to obtain a mo re accurate estimate of the failure pressu re of a corros ion defect. by taking into account the actual (river bottom) profile of the defect.
•
RSTR ENGTM has been validated against 86 burst tests on pipe contain ing real corros ion defects .
77
USING THE ACTUAL SHAPE OF A CORROSION DEFECT - RSTRENGTM's River Bottom Profile
39
USING THE ACTUAL SHAPE OF A CORROSION DEFECT - RSTRENG •
T he RSTR ENG method is bas ed upon the effective area and effecti ve length of the corrosion defect. Any shape of corrosion defect can be assessed. all that is required is a river bottom profile of the def ect.
•
Determining the corrosion defect profil e requires a large number of depth measurements 10 be taken at regular interva ls alo ng the length of the defe ct (tracing out a river bottom profile ).
•
The defect can be a single defect or a com posite defect formed through defect interact ion.
•
T he procedure is based upon cons idering various subsections of the tot al defect profile , and predicting the corresponding failure pressure. This process is repeated for all possible com binations of the various subsections. In m ost cases , alth ough not all, RSTRENG pr edicts a m inimum failure pressure that is less than the value predi cted using the exact area , total leng th method .
•
2OOli_
USING THE ACTUAL SHAPE OF A CORROSION DEFECT - RSTRENGTM's Method > 1 1,2
1,2,3 1.2,3,4 1.2,3,4,5 1,2,3,4,5,6 1,2,3,4,5,6,7 1,2.3,4,5.6,7,8 2 2,3 2.3,4 2.3.4.5
I- -
A
A, A I 1- - A, .1f
": =--i'-, a
if '" SMYS + IOksi _
oRSTRE.SG"I ~ l'QfUQ10 n'l"':r (om bi,..,tion 0/ A/Ao and I o TIr~ (om binatio n gn';n g th~ lo .. ....sz/ailurt . lrtH is oblQin~d
~
_
..'••
.
..'G_
"
__ • _ _ <--.. ..
"
~:::::':':':': :':7
'
C_
_ _ .'..... "'"
80
40
USING THE ACTUAL SHAPE OF A CORROSION DEFECT - DNV·Rp·F101 • The basic principle is to consider the actual profile as a collection of 'pits' within 'patches'. • The assessment method then determine whether the defect behaves as a single irregular 'patch', or whet her local 'pits' within the patch dominate the failure. Potential interaction between the pits is also assessed . • A progressive depth analyses is performed. • The corrosion defect is divided into a number of increments based on depth, and modelled by an idealised 'patch' containing a number of idealised 'ons'.
• The idealised 'pits' in the equivalent pipe are assessed using the interacting defect method .
"
USING THE ACTUAL SHAPE OF A CORROSION DEFECT - DNV·RP·F101
•
- I - I-
'll '-1-+-- - -
-, '-- - - - - - - - - - - -- - - - - - - --'
c
_ 82
4t
USING THE ACTUAL SHAPE OF A CORROSION DEFECT - DNV·RP·F101
1-' ; ,,
•
~. ~
,.4- - - - - -
"-1',,- , I
,
•
I
...;/--i-
J-.r=I ~._~,. -
I
• t,
·",,--1
••
.II
Spreadsheet? 83
ASSESSMENT OF GROUPS OF CORROSION DEFECTS
•
D_2'ODI~
.. 42
ASSESSMENT OF GROUPS OF CORROSION DEFECTS - ' Int e ra c t io n' Distances
d'i _ L
. - _ , _ - - - - - - , - - - - - .""'-
0_2005_'
85
ASSESSMENT OF GROUPS OF CORROSION DEFECTS - Interacting Defect Size
990
•
L - -~,- _..'-:_' L - - - -r - - - -- J
: 0: ,' ,,
"
:
:
"" "
cS
I
Width
,
~I 1----~-----·------: ,
Length
43
CORROSION DEFECT (DEFINITION OF DIMENSIONS) [ADJACENT (INTERACTING) CORROSION DEFECTS]
7~
I\
Defect 1 : L/~m." / :
~ __ ~/ __ l -----,-_ Pipe Axis ---L--_
i -- - -~- _ . ----- -
: ~
,,, ,
,
s
© Penspen Group Ltd
------ -- ----- -
------Defect 2
~I
ASSESSMENT OF GROUPS OF CORROSION DEFECTS - Published Methods
• RSTRENGTM • DNV-RP-F1 01
co p ""","" 2006 R..61'
87
ASSESSMENT OF GROUPS OF CORROSION DEFECTS - Simple Rules •
SOME SIMPLE INTERACT ION RULES ARE: • For in-line defects , if the axia l separation is less than the length of the shortest defect then th e defects inte ract.
•
• The length of the com bined defect is equal to the sum of the length of the ind ividual defects and the separation between them .
• For circumferenlially spaced defects, over lapping in the longitudi nal direction , if the circum ferential separation is less than or equal to the wal l thickness then the defects interact. • The length of the combined defect is equa l to the overa ll longit udina l length.
""-'" ' c.... . . _
~
~
. __...
_
""'""
"-' . _ PR,..",._~~,
.
oJ ,." ..
-.
."" , ' _
PoI_
~_
c _
"',,,. "'
. _
. . _"
88
44
ASSESSMENT OF GROUPS OF CORROSION DEFECTS - Simple Rules •
There are other simple rules . For example:
• For in-line defects, if the axial separation is less than 1- (or t) the defects interact . • The length of the combined defect is equal to the sum of the length of the individual defects plus 1".
• For circumferentially spaced defects, overlapping in the longitudinal directio n, if the circumferential separation is less than or equal to 61 the defects interact. • The length of the combined defe ct is equ al to the overaliiongiludinal length.
P
<1" (25mm) or
O_:lOllIl_
--_.. . _--_.__... _ _.
..
e.---. .• -. _
~ - <-
. _.. _-
89
ASSESSMENT OF GROUPS OF CORROSION DEFECTS: Simple Rules for axial corrosion
m
mutm m umummj. · ~~····· u ... m·· · · t F .
2C'
2c,
2c =2c 1 + s+ 2c2
V -I
"d.I-: -)--.. \~-T:) i~ 2c,
I' .
!
s ,
• j - - ,-
2<:.
I~'
You then use '2c' and 'd' in your failure equations 90
45
ASSESSMENT OF CORROSION ON WELDS •
It is generally considered that longitudinal co rrosion across seam welds (other than autoq enous". e.g. ERW and FW) ca n be treated as corrosion in parent plate (BS 7910. AS ME 83 1.4), with supporting test
data": • Weld properties must be similar to the line pipe [
•
__ __------_ ._-----__ __-- -_____------_.__ __ •
...
DNV RP F-101 can be used on seam and girth welds (see code for co nditio ns)
Compressive longitudinal stress can red uce burst pressu re.
...
o"--~_ ,
....
.....,- _.__ . -._ . ----._. ..- .. "':.._.__ __ ._. __ . .. _. .. ._---'---"'-""' ::.:~:=;=.:.. " :" .=:.. ~_
91
_~-_.
OTHER CONSIDERATIONS ON BURST STRENGTH OF CORROSION - External Loads
• DNV-RP-F101 • The method assumes that the failure surface follow s a Tresca criterion, i.e. a tensile axial stress does not affect the burst pressure , but a compressive axial load reduces the burst press ure in a linear manner. • A rectangular defect profile is ass umed. • The met hod is only applicab le if the total axial stress (including the cont ribution due to the internal pressure) is compressive.
92
46
OTHER CONSIDERATIONS ON BURST STRENGTH OF CORROSION - External Loads Tensile (internal pressure) failure criteria
Combined pressure and compression
Compressive failure
93
criterion
CONSTRUCTING PIPELINE DEFECT ASSESSMENT ACCEPTANCE CHART
•
47
A PIPELINE DEFECT ASSESSMENT ACCEPTANCE CHART - Step 1 ••• Failure Line ' .0
I
CRI TICAL DEFECT SIZE AT 72% SMYS , NO SAFETY MARGIN
" - "
DEFECTS IN THIS AREA WO ULD FAIL
0
"" ""• ..
0.'
a-
d
,
1 -
:!...L =
-
I
~
d I --M
,
,! M DESIGN PRESSUR E (72 percent SMYSj
"•s "
'l5 o.
;
l o., "e ,.
I DEFECTS IN THIS AREA WOULD NOT FAILJ
"
> .,.".".
"
" O_
e.e
"
00 ae <0 2e1(Rt)" O. 5 (no rm alised defect leng th)
"
"
"
00
....., :IOOlI Ro.-5l1
95
A PIPELINE DEFECT ASSESSMENT ACCEPTANCE CHART - Step 2 ••• Safety Factor 1.5
,------,-;;:= = = = = = , • Actual fa ilure stress of defect free
linei>iPe Os UTS or
~ 1 .15 . S MY S
' Th e maximum pressure a pipeline will expe rience, may be well above MAOP. ...
1
0.5
o Design
Hyd rot est Overpressu res ' 8L ~ ~
C P.....,..,2006R..61,
' Methods such as ASME B3 1G have built-in safety factors that allow for these uncertainties, but it we are producing our own fa ilure curves , we MUST use the m aximum pressu re the pipeline will expe rience as the failure stress , and this may be Failure >MAOP
T "",",... ,- ... .."."_ , _
"-""_ _
-Most codes allow (typica lly) 10% (of MAOP ) overpressures.
;. " ...."," """",, "",, _
"",_ " " " , ",
~ on """ '_'_ ' '''"'''''' , '',,,,,", '''' 200' , P _ A RC- ''
48
A PIPELINE DEFECT ASSESSMENT ACCEPTANCE CHART - Step 3••• Acceptance Line
..
CRITICAL DEFECT SIZE AT 100% SMYS. NO SAFETY MARG IN
" - "
~
.....
"•u•• "
-
I -
d
d
1 -
1 M
.e "
•
-e
•• " .0 'a
~
oS ~
-e
. . .. .." . .
HYDROTEST PRESS URE (100 percent SMYS j
DEFECT S IN THIS AREA WO ULD NO FA IL AT 1000/0 S MYS
"
.. .. ..
..
"
2c1{Rt)"O.5 (no nna lised defect le ngth)
C_2OOI-.
"
A PIPELINE DEFECT ASSESSMENT ACCEPTANCE CHART Step 4 ••• Failure, Acceptance & Safety Margin
..
I
"
-s: "
"u-8
~
Failure
-
"
01
... ..; o.
r "
:--
• e•
ii o.
DESIGN PRESSURE, (12
SiEl y Magn
E
";' n HYDROTEST
~ n
.. "
-
I 1
-
d
-
I
d -M1t
i fOlOl'l l SMYS )
t:
PRESSURIZ( 100 ~ SMYS )
Acceptance
.. .. .. ..
••
.. ..
2c/(Rt )AO.5 (norma li sed defect leng t h )
C_2OJI_l
"
.. 98
49
A PIPELINE DEFECT ASSESSMENT ACCEPTANCE CHART· Failure, Acceptance & Safety Margin
.
I
" -< "
" "• .. in ~ "
X
~ ~
DE SIGN PRE SSURE
X
Ii , .
stay Magin
E
! u
- 1-
d
,
1
--
"
In peroenII SMYS)
n C OCf'PIo!::Je
HYOROTE ST PRE SSURE ( 100 peroenl SMYSj
~ "
.. "
"
-d,
I -
'!....L. _
X
..
"
Ilazphbk.
.. .
. ..
" 2cJ(Rt)AO.5 " (normalised defect length) "
O,,- 2ooe_'
99
A PIPELIN E DEFECT ASSESSMENT ACCEPTANCE CHART - Failure, Acceptance & Safety Margin ' .0
09
•
~ 0.8
FAILURE
:: 0.7
!
~ 0.6
s
~ 0.5
~a
0.4
i
0.3
MAOP OR DESIGN PRESSU RE (72% SM YS)
~
... 0.2
H YOROTE ST PRE SSU RE 1100% SMYS )
0' 0.0
0_2001_
o
2
3
•
•
6
norm.alised d elKtlongitudln;ll"ngth (2c1(Rt)"")
7
6
' 00
50
A PIPELINE DEFECT ASSESSMENT ACCEPTANCE CHART· Example
I uf
o
'"'
!l o
-
0
o
I{
1\"
,'~..;•.~ .• . • o o
O_2OOt_
I
<,
• 0
~r
I
' • I
I
•
[ I-~ /1 J 1- - -
1'\1
I
= O.9UTS
I
-... _-._._r~fqtt f. efor --MeAt r-. 0" ~d
• I
Q
on l1 y
{
S
Corrosion Length (mm)
'11
'"
PIPELINE DEFECT ASSESSMENT FIELD CHART· Example
102
51
ADDITIONAL IN FORMATION
'03
ASME 831 G - Curve for Obtaining 8
•
4.0 +-- , B= 11 [ l.ldll-O.15 d/'
30
J'-
1
L 5, 1.1 2B.[i5i
• 2.0 '.0
0.2
04
0.5
08
"4
52
A PIPELINE DEFECT ASSESSMENT ACCEPTANCE CHART - Failure Line \l
..
FA ILURE A defed c:I depth 6O%wt, and or tllis length, will fa~ allh is
stress l e ~ el
~
u, u
d
•
d ~
1 ~-
"
. 2c/(Rt)"O.5 (no rmalise d defe cll ength) D"-2OOIl 1l
'"
AXIAL CORROSION DEFECTS - Failure Curves Po
. 5
••
..•••
For a short shallow defect, or no defect, the failure pressure is equal to th e failu re pressure of the pla in (undefactlve) plpe:
~
c,
• • •
[Pol
Increasing defect depth
~
2
For a very long defect. the failure pressure is equal to the failure pressure of the reduced crosssection (as jf it were a plain
~
(undefectlve) pipe):
Ll!'o(1 .d~)l
D_2OOIl _ '
2c/JRt(normalised defect length)
",.
53
OTHER CONSIDERATIONS ON BURST STRENGTH OF CORROSION - Long Areas
•
Some work has shown tha i defe cts longer than approximately the pipe diameter behave as infinitely long defe cts:
•
•
Ot her definitio ns of infinite defects are. .. 8(01)05, 0.750 , and 4.48 (0 1)°5, (90 .2 Dtf 5
. ,," -
Tests" at Petrob ras , Braz~ have shown most
assessmentmethods to be ~ co nservative wnen assessing
i
long corrosion;
•
• A SME 8 31G could be overly conservative I RSTRENG Effective Are a and the • DNV l RP-F l01 (Part B) are conservative I RS TRENG (using O.85dL) is I• • non-conservative.
:~,,-
2OOlI _'
. _.-
-. _-
"~.
• • • , •
, '" , "
.. . ", .
'.
"
•
"
'-
..~
• "
.
"
-_ _-_ _._----_._.- --.. ---- -,--
..._-. _ _ . _ .. _ _ _..R'._-_ _' _ ~
=~-::::. ::.~_
,
,
, -,.... ..-
"
,
0_
,,"
•
"
• "
..
" ",,",POl " "
"'.", e....", P,..... .
I
.
_ " _ . _ . _ _ _ _ R'.
_ _ . _ -- -
~-~--- ,--
'"
OTHER CONSIDERATIONS ON BURST STRENGTH OF CORROSION - Long Areas • •
All the main methods (ASME , DNV ) allow for long defe cts. The long defects tend to infinity, therefore the M or Q factor tends to • infinity, and the equations go to:
• Failure stress = Flow stress x (1-<111)
1-0_2001_
,os
54
~;~]
a, = O.9UTS [1
DNV RP·F101 • Safety Factors
• Two alternative approache s are given for the assessment of corrosion: • The first approach in acco rdance with the safety philosophy adopted in the DNV Rules for Submarine Pipeline Systems (DNV96). • Uncertainties associated with the siz ing of the defect depth and the mater ial properties are specifically considered. • Probabi listic calibrated equations (with parti al safely factors) are given .
• The second approach is based on the ASD (Allowab le Stress Design) format. • The calcul ated failure pressure pressure is multip lied by a single safety factor base d on the origina l design factor. • Consideratio n of the uncertainties associated with the sizing of the corrosion de fect is left to the judgement of the user.
O Pon- , 2006 Re.61'
109
EXAMPLE OF EFFECT OF EXTERNAL LOADS ON DEFECTS THAT FAIL UNDER AN INTERNAL PRESSURE: Failure Curves
(1
Wide, circumferential defect
'0 "'-"' -_, no com:d-p,eSSive stress (0, ;" 0) 0.9
---- - ~_
~ 0 .8
~ .l:
0.7
------ --- --------------------
p" rrJ2
• -------
0~ 0.6
Unrestrained
"
Partially restra ined
~ 0.4
Fully Restrained
""• .e
'a E 0.3
•
e 0.2 0.1
This is a sub-sea pipeline, that is subjected to compressive stresses from temperature changes. Comp ressive stress decreases the d feet size that fails at the internal pressure 2
3
4
5
6
7
8
9
10
n ormalised defect lo ngitu d inal len gth (Zel (Dt )" ')
'"
55
How to Assess Gouges
Penspen Integrity
..--- .......
1
LECTURE OUTLINE • Third Party Interference • Protection
•
• Go uges • Notes
0_2001_
,
THIRD PARTY INTERFERENCE & DAMAGE
__ 2OOlI_,
a
THIRD PARTY INTERFERENCE & DAMAGE •
One of the main causes of the failure of onshore and offshore transm ission pipelines is 'Third Party' or 'Externa l' InterferencelD amage • Also known as Mechan ical Damage /Int erference
• •
It is the major cause of transmission pipeline failures in North America and W estern Europe. Third party interference can cause: • a puncture • a metal loss defect (suc h as a gouge), or • a geometr ic distortion of the pipe shell (such as a dent), or • a combinatio n of the a dent and a gouge • Dents containing defects are more severe defects than dents or defects in isol ation • They can have low failure pressures & short fatigue lives. • Consequently dents with defects are regarded as the most sev ere form of mechanical damage.
0_2OOlI_
•
2
THIRD PARTY INTERFERENCE & DAMAGE
,
0_2005_
DAMAGE: Punctures , Gouges, Dents _T he numb er of times people dig into the underg round infrastructure illustrates the huge frequen cy of excavation:
ethere were an estimated 13 million exca vation notices issued to utility operators across the United States in 1996*
---_
_The actual number is highe r because some excavators do not use onecall notification services.
._ '_
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'..,""""TSM;....''O ,"'
......
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3
THIRD PARTY INTERFERENCE - Example: Puncture
• This 3rd party damage- was caused by a constructor beginning work before the agreed time in a One Call notification process
•
This third party damage* was caused by a constructor who failed to use the One Call System
,
Dig ~Safel y. 1 .8 00.112 2 .1 118 1
w_. uncc.org ..", .Ooo _ _
._
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THIRD PARTY INTERFERENCE - Example: Gouge
Reputable, safe equipment that works close to our pipeline can gouge it, if not carefully driven @ Penspen
,
4
THIRD PARTY INTERFERENCE - Work on Pipelines Can Cause Damage
s
TYPE OF MACHINERY CAUSING DAMAGE TO UK ONSHORE PIPELINES '
~
~
TYPE OF MA CHIN E
~ -~
•
•
T he use of Back Acters and Digg e rs acco unt for -54% of all damage incidents and 28% of p ipeli ne failure s. T he use of power dri lls acco unte d fOI <4% of all reco rded damage incidents, but - 43% of pi peline fa ilures.
C P _ 2OCJ6 " .. 61' ·M_ _
' _ . ~W
__' _
No. OF DAMAGE INCIDENT S
S
No. OF FAILURE S
FAILUR ES: INC IDENTS
Bac k Acter
165
3
Digger
137
6
0.04
Others
60
4
0.Q7
Powerdrill
21
9
0.43
Plough
11
3
0.27
Trencher
10
2
0.2
Dra inline
9
1
0. 11
None
7
0
0
Spike
6
0
0
Tra cks
6
1
0. 17
Drag line
4
0
0
Scrape r
4
1
0.25
Bull Doze r Blade
4
2
0.5
Unknown
110
0
0
TOTAL
564
32
0.06
"'_ " "" - "" _ ""' _
__ ' _
__ " _ _ ' _ _ _ _
_
0.02
_ ""_
--'
16
5
METHOD OF DISCOVERING DAMAGE FROM THIRD PARTY ACTIVITIES ' (UK onshore pipeline data) DISCOVERY METHOD
No . OF DAMAGE INCIDENTS
No.OF FAILURES
150 138 130 63 29 25
Site Contractor Ground Patrol Other
Pearson Survey A ir Patro l
16 0 8 0 0 3 3 0 2 32
,.
Unknown Public
13 2 564
On-line Inspection Police
TOTAL
.The air patrol gave the first sight ing of activity In 30 - 60% ctincidents .
' A consi derable numbe r or activities were miss ed because of their sho rt duration . ' Betw een 60% and 90% of the lolal encroachment activities lasted less tha n 2 weeks. C_
...
_._._. __._-_.-..
2llO5"-611
_-
---
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- -- ..
_ .-..-~
--
...
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tt
FAI LU RES DUE TO THIRD PARTY INTERFERENCE •
1989 - San Bernidino, California , USA •
14 in. diameter gasoline pipeline at 1680 psi,
• Dent and gouge damage ruptured causing two fata lities .
•
1993 · Reston , Virg inia, USA • •
36 in. diameter fuel oil pipeline failed , 9000 barrels of oi l contaminated the
Potomac River. The damage was about1Q years old . 1999 - Bellingham. USA •
•
• •
•
16" liquid tine failed. Three fatalities . Damage was dents and gouges from th ird party interference
2000 - Abilene , USA • 12 in. diameter natural gas (?) pipeline owned by the Mobi l P ipeline Company failed resulting in
•
offICer).
1993 - Teje rtas. V en ezu e la •
O_ _
ooe fata lity (a police
Contractors install ing fibre opti c cables sever a natura l gas pipeline adjace nt to a busy road . More than 50 people killed in resulting fire. Two contractors jailed for 16 years
2OOl5~'
"
6
THE EFFECT OF MECHANICAL DAMAGE •
TIMING• IMMEDIATE FAILURES : Mechan ical damage can result in immed iate failures. by equipment punct uring the pipe line • But- 20% of the tim e. the equipment fails to puncture the pipe, Of cause damage severe enoug h to immed iately ruptu re il
• DELAYED FAILURES: Medlanical dama ge in a pipeli ne can ca use 'delayed failures' • Only about 20 to 33% of mecharjcal damage incidents res ult in 'delayed' failures (failu res ocaming som e time after the dam age eve nt) • but these have had serious consequences. ~_:ICOlI_,
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1
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e - _ ., " ' .
THE EFFECT OF MECHANICAL DAMAGE (eont.) •
COST: The immediate failures tend to result in a lower cost. This is because: • work is ongoing on the line. and • the operator is usually aware of activity . and can respond to it quickl y {e.q. reduce the press ure and close valves) •
•
This is particularly true of oil pipeline failures. where the cost of an imm edi ate failure can be a fraction (say a third) of the cost of delayed failures
SAFETY: Immediate failures have the most severe implication s for safety •
fOf gas pipeli nes the immediate failures will cause the vast majority of casualties
•
delayed failures usually mean tha t people (those causing the damage) are no long er around . but resid ent population sU at risk
"
7
THE EFFECT OF MECHANICAL DAMAGE: Delayed Failure* _ A delayed failure from mechanical damage :
·,._ ....P'........ '_ e...a,. _ t>a
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W '"""""'.•_ ""' ,.,
'""
THE EFFECT OF MECHANICAL DAMAGE: Leaks versus Ruptures" _ Mechanical damage causes more ruptures than leaks. a c orrosrc n causes more leaks than rupture s. No. of Failures
7000
6000
No. of Failures
800 .,,-r_ In ' Co rr o _ lo n D h . C.... o . 'o n
• D. m a D_ by o'h e , .
5000 4000
• C... ttuetlo n D. m a g .
_D .h..
_ W. ld
3000 2000 1000
o
=..
-
~ LEAKS
. 'n' ".." ,.."
- - - - - - i 'C h .
700 .u-- 600 J,-J-- 500 .u-400 .u--
. C ~ ." Q C " O~
. w.,..
n o, ~
• ••
o. .... U .
_ Ot U , •
-
300 .u--
-
200 .u--
-
100
co
• Da ma g e by
m ""iJC
O -~-
RUPTURES
8
PROTECTION OF PIPELINES
"
PROTECTION OF PIPELINES: Cover
_Depth of cover is an effective method of protection. a c oces require a minimum depth of cover of e.q. 0.9 m (2' 11") - 1.1 m (3' T') _ Research work * showed that the likelihood of damage is reduced by a facto r of 10 (rural area) and 3.5 (suburban), as the depth of cover is inc reased from 1m (3' 3") to 2m (6' 7"). " "
J,
j,
./
!',
.,
"
"
_. ----.. ",-
"
. .
9
PROTECTION OF PIPELINES: Wall thickness _Increased pipewall thicknes s offers prote ction against damage .
More Protection
_ For example very few (about 5%) of excavating machinery used in suburban areas will be able to penetrate 11.9 mm (0.469") wa ll. _ T his accounts for the small proximity distanc es specified in some codes
()
}
C_2OlI_
"
PROTECTION OF PIPELINES: Wall thickness and Resistance to Puncture . Pipelines have inherent resistan ce to puncture from excavat ing machines. _ T he draft A S 2885.1 giv es the following relationships (Se ction 5) for Pipeline Puncture Resistance (kN ), Rp :
. R, =N{ I .17-0.0029{DItJ}.{L + w}.{t. - Digging Puncture Force , Fp • (kN)
+
= O.0231 496.~ 826007 for WS20 ,OOOkg
_ Digging Puncture Force , Fp • (kN) = f .5{O.0231496. YlJ826007) for W>2 0.000kg
.t . .D _ L,w
•.u . .N •N
.w
= pipe
wall thickness, mm = outs ide pipe diameter, mm = length, width of digger tooth , (o btained from a Table ) = ultimate tens ile strength, MPa = 1 for single tooth penetraton = 2 for twin pointed 'tiger' leeth. = operating weigh t, kg
R, ~ 1. 1 0Fp
Risk of puncture Negligible
High
<0.98Fp
Certain
10
PROTECTION OF PIPELINES: Sleeves . Pipelines protected by sleeves are no longer popular due to difficulty in maintenance, and the possibility of corrosion (and the difficulty of finding it). _Thicker waited pipe is prefe rred , alth ough care must be taken in installing the pipe , and the coating mu st be closely monitored
O_2OCl5_
"
PROTECTION OF PIPELINES: Marker Tapes _ Th ere are some threats , for example horizontal directional drilling, or deep ripping, where buried marker tape is clearly not effe ctive .
.....
-
... __ ._.-
,-;:e:=:
11
PROTECTION OF PIPELINES: Marker Tapes & Protective Plates/Slabs T~"pt o f
P re teetion
~ o.
of
Summ aryef Tesrs
I<"!iU
Dam a Kt Redu ction
Faeter No Protect ion
Warnin g Tapes above the pipeline 3 m wide conc rete barrier above the i cline 3 m wide concrete barrier above the i cline. combined with warning ta cs 3 m wide yellow striped steel plate above the pipeline combined with warning
2
, 16
IS IS
Pipe line damaged in both tes ts Pipeline damaged in three tests Pipeline damaged in three tests No pipeline damage observed in an lest No pipeline damage observed in any les t
1.67
5.33
' IS ' IS
ta es
C_2005_
GOUGES
-
1'_2001_'
"
12
GOUGES •
A gouge is surface damage to a pipel ine ", caused by foreign obje cts rem oving part of the pipe wal l.
•
A gouge is a mela l loss defect. • line pipe stee ls are highly resistant 10 part wa ll defects, and such defects • They record high failure stresses due to the inherent ductility and toughness of the steers. PROVIDED they are not associated with a de nt.
_--------_ ...
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_
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as
GOUGES - Cracking & Hard Layer • Gouges are treated with caution because of the possibility of :
•
• Associated denting: • Cracks can often fo rm due to "reroundlnq" of the dent. and _______ • The risk of a work hardened layer below the
gOUT
/--V - - ......
,/ ---------"'"
Cradl ing
13
GOUGES - Cracking & Hard Layer •
The risk of a work hardened layer below the gouge : • This 'hard laye r' is caused by the heat of the damaging process and the plastic deformation. • Max depth is - n.smm
Crack ing
• T his har d zone ma y reduce the local du ctility and may crack as the ind enting force is rem oved and the pipe atte m pts to regain its original shape.
Hard layer
C_2OClS_
-1
-'
AS 2885.1 says: 'Some references suggest thai only vel}' large plant can gouge the wall thicknes s to a depth of more than 4 mm.'
"
GOUGES - Cracking in hard layer' _N ote crac king along ed ge of go uge
•
••• "-""""""'
8 Note brittle cracks initiated in cold worked zone . This zone if hard an d high strength - may be susceptible to en vironmental cracking
~
"'
....... OI_Goo _ _ ..... " " " . ..
"
14
GOUGES - Hard Layer . In the goug e', we have: aplastic flow, e metat tr ansfer,
s eve n re-melling due to the heat of friction would have occurred at the contact point. _For some depth we have a microstructure that is crushed & severely cold -worked, loca lly degrading the ductility & toughn ess. _ In the assessment of a gouge, account will need to be taken of any hardened layers below the gouge and the effect of low toughness material.
'Note the severe ly c rus hed microstruct ure in the gouge just below t he pipe s urface
_Th is may require an assessment of the line pipe toughness prior to assessment or inspection of the defect.
GOUGES: Effect of Toughness •
There is a risk of failure at a low stress if a meta l loss defect is present in low toughness line pipe, due to low ductility or brittle fractu re initiation . For example : •
•
•
Tests by British Gas. showed part wall defects in lowe r toughness line pipe (213 Charpy = 20 J or less) record ed lower failure stresses than similar defects in higher toughne ss (greater than 213 Charpy = 42 J) .
The effect of the toughness and the hard layer on the line pipe steel has been investigated expe rimentally. •
Research work in Canada (carried out by CANME T) concluded that the defo rmed layer assoc iated with the gouge was not deleterious in line pipe with a Charpy toughness of greater than 20 J.
15
GOUGE· A Longitudinal (Axial) Defect Dimensions 2c
© d 2c
t R D
= = = = =
defect depth defect longitudinal length pipe wall thickness pipe radius pipe diameter
"
GOUGE· A Circumferential Gouge
16
GOUGE· A Circumferential Defect Dimensions 2c
..... -.....
d 2c
C_2lXli_
defect depth defect cir cumferentia l length pipe wall thickness pipe radius pipe diameter
=
=
t
=
R D
= =
---.. __
.......
-
AXIAL GOUGE - Collapse and Bulging _ The methods assume that failure is controlled by 'plastic collapse' _Opposite is a failed gouge in laboratory test _ Note extensive deformation (plasticity) and 'bulging' - - -
L---=::I LJiI-.::I
....---..,.
17
AXIAL GOUGE· Assessmen t Model
Af =
-I
.,
I M
}
j 2c )' I +O.2'\. JRt
0;
;
;
hoop stress at failure now stress
d
=
2c
;
axial length of gouge
t
=
R M
;
pipe wa!lthickness pipe radius (=D/2) Folias facto r (bulg ing factor)
gouge depth
=
as
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Il
AXIAL GOUGE · Test Data ow
~ d
at =
1- -
I
d 1 1 M
1- - -
x_.,,~,
"• ,.0 .60._,_ • a.. .... TOIl' •
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f ~
• '" D •• •
~
.
)':"
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•
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UNCONSERV4TIVE ; ,
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)( 1-10."... .. . . .192
~
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11 111J1
... rw" ge2
e
in
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CANM ET T.... (,~ee)
l' CSI.l S"""l EUROPII'E 2000
;;) 120
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~
•
• CO+lSERV4nve
V···
,. '.
.. ec eo • eo Measu re d Fail ure Stre ssNleld Stren gth , % •
O_
2OOlI Ro.fW,
~
,~
ae
18
d
,
1- -
d I 1- - , Ai
AXIAL GOUGE - Basic Assessment Model
FAIL NO FAIL dft '" 0.4
0.5 0.6 0.7 0.8
. I-
•
Cl_OllIOIl_
-l
,
,
• 2cJ(Rt)"O.5
•
•
,
0.' 0.95
•
---",,,._-
"
AXIAL GOUGE · Leak/Rupture Behaviour
19
AXIAL GOUGE· Leak/Rupture Behaviour Gouge length
"
B
RUPTUR E
f I -=M
LEAK
CY
. '--------------------~ ,
•
2c1(Rt)"O.5
•
•
•
---_.",._-
CIRCUMFERENTIAL GOUGE· Assessment Model
7](ff - ,8[1-17])
f _CY_ CY
--'--'-----.---'----'---,-----'--7----c I rpt + 2[1- 7] ]sin (,8)
,8 =~ R
"!.
=
a
=
d
=
2c
t
= =
R
=
d
7] = 1- -
t
axial stressat failure flow stress defect depth (with allowance fix hard layer and cracking) circumferentiallenglh of defect. pipe wall thickness pipe radius
. 20
CIRCUMFERENTIAL GOUGE FAILURE· Case Study _ March 1997 ; Reduce pressure in transmission line: . Pressure reduced lo 30 psig in 20" pipeline due 10 road c:onstruclion wort< in the area
_ May 1997 : Directional drilling operation . To instal an S" diameter steel nalural gas distnbution main para llel to the transmission pipeline.
_ July 1999: Failure . As opeI'3tor began 10 return the 2Q.fndl tnl nsm ission pipeli ne to lui service .
"'._---,.,._ -__. . _.0_. ._-_.._-_ ..__..__....----_ . _ ..... ... _--...... --.-.- ... _.. _-.--_.. ---.------._-- ~_ ._-_ ._
"
ASSESSING A GOUGE - Notes
•
21
1 . ASSESSING A GOUGE - Assessment and
Consequences _ ASSESSMENT - Gouges can be assessed providing your pipelin e has a toughness >20J. _ Nole tha i a gouge needs to be checked for possible fatigue crack growt h in some pipelines (e .g. some liquid lines).
_ Allowance (e.q. addin g O.5mm to defect depth ) for the hard layer or su b surfa ce crac king is advisable , if they are to be remain in the pipeline,
_ Also, ensure there is no risk of environme ntal cracking, and no problems from cyclic load ing (see later).
_CONSEQUENCES _ Think carefully of the consequences of 'getting th ings wro ng'. If your damage is in a pipeli ne in a 'high consequence' area , you should inspect the damage dosely before assessme nt , and include appropriate safety factors in your assessment.
2. ASSESSING A GOUGE - Inspection _ If you detect a gouge in the field , you should check : _ FOR SUR FACE CRACKING
a r here may be some crack-like indica tions (spalling) caused by the damaging object.
...
_ If the crac king is deep , it may be indicative of a gouge that has cracked due to den ting (the den ting may not be visible as it may have been 'pushed out').
,
_ This is severe, and requires repair.
--- ---'''-'
~
...
22
2 . ASSESSING A GOUGE - Inspection (cont.)
. If you detect a gouge in the field, you should check: _ FOR EVIDENCE OF DENTING
_ The impact ma y have also dented the pipe. _ Residual denting aroun d a go uge is seve re - see later
0
_
3. ASSESSING A GOUGE - Inspection with Pigs . PIG DATA : Mos t meta l loss pigs are designed to detect corrosion defects, and may be inaccurate! unrel iable in the detection of narrow defe cts
such as axially-orientated gouges, _ Some cttn e newer pigs (e.g. the 'TFI' pigs ) can de tect axial defects . _ Alw ays consul t your pig pro vider .
_ So me pigs can de led geomet rica l anomalies (e ·9 . denting) and som e pigs can detect metalfoss (e.q . corrosion). _ Ha.vever, there is no curr ent pig thai can do both .
_ _.... _
• Therefore. if you are basing your gouge assessment on pig data , you mus t be co nfident that the pig has found a gouge and any associated denting (if present). • You may need to excav ate and inspect gouges , to confirm dimensions, and absence of cracking and/or denting 0""'- 2008_
1
"-"11 ..
.. _ _ 46
23
4. ASSESSING A GOUGE - ASME B31.8 _ ASME 831.8 (2003) has chang ed its gouge requirements: it requires gouges of any depth to be repaired _ ASME (1999) formerly allowed gouges of 10% wall
thickness to remain. provided they were not associated with a dent. 8 This more severe approach is in recog nition of the known severity of mechanical damage . and the fact that a residu al dent may be ove rlooked around a
gouge· , _ Other standa rds are not as severe, e.g. AS 2885 .3: 8 Gouges, grooves, notches <0.25mm 'harm less ' . >0.25mm but S10%wall thickness can be removed by grinding _ Wall thickness loss due to grinding may be assessed in the same manner as corr oded pipework .
·.. '_.I1_"'_e.-.. _ _
eono..-. 0" 2
I),.....
O'C:!OOMl'l»
..
_~
..._
5. ASSESSING A GOUGE· Repair _REPAIR - Gouges can be removed by grinding (grind depth not too exceed limits calculated using previous equa tions + safety ma rgin), or repaired by sleeving. Areato be
_G RINDING - grindin g a goug e can remove hard layer (elimina tes possible cracking problems and possible problems of env iron mental attack of the ha rd layer) .
removed
_ If you have g round you r def ect, and
it is clear of crac king , and acceptable to your standard equations (with a safety margin ), you can recoat and not repa ir Ground area can be assessed usingASME B31G
I
24
1 ASSESSING GOUGES: Summary • Gouges: • Burst: Use Battelle equations but allow for any hard laye r/cracki ng ('d..') • Remember to include a safety factor when using this equation
• Fatigue: Use as 791 IAPI 579 t assess your gouge for fatigu e -grOwth. if the pipeli ne is subjected to cyclic stresses
1_ d + d,
_" _I "
= _--;--"';---;-1 1_ d +d, _I_ I
M
•
• Caution : • No denting must be present in the vicinity of the gouge. • ASM E 8 31.8 does not allow gouges: they all must be repa ired .
"
•
25
How to Assess Dents*
Penspen Integrity
T.... lectJre_noe ~ 1 h < I elIectgf ""'....... pr-...on d o o n I s ; ~._ _
pressure
~_._
_
(tor.~.in""'_l"'requino~""'-"
_ _
_
_
11_1
1
LECTURE OUTLINE •
Plain Dents • Burst Strength • Fatigue Strength
•
Dents containing welds
•
Constrained Dents
i
,I
• Rock Deni s
•
Dents and Gouges
•
Dressing Defects in Dents
•
Other Geometri c Defects in Pipelines
,
THIRD PARTY INTERFERENCE & DAMAGE
a
THIRD PARTY INTERFERENCE - Example: Dent •
This dent was detected by a 'smart pig'. • 26" line in Japan, • The dent was at the 4 - 5 o'cl ock posi tion, possibl y caused duri ng installation.
•
Note how close this damage is to a mOlorway to ll booth
_ _ ...... ..-..... _ 0
•
2
THIRD PARTY INTERFERENCE': Scale •
We know thatthird party damage is a major cause of pipeline failu res
•
Dents are found in the majority of (>80%) pipelines insp ec ted using smart pigs, with 50% of pipelines conta ining 10 or more dents
•
A review of pig dat a from 63 pipelines revealed : • 9851 dents of unknown sizes were reported by meta! toss pigs • 2389 (24%) of these 985 1 dents we re reported by 'caliper' pigs thai are specifically designed to detect dents, but note that it is assumed that these caliper pigs were only reporting dents of depth of over 2% pipe diam eter • This suggests that 76% of the 985 1 reported dents were <2% pipe diameter in depth
>80% pipelines contain dents
cK-_ Most have depths of <2% pipe diamet er
This gives 1 A dents/km s
'"'
THIRD PARTY INTERFERENCE': Scale (eont.] •
These dala give a den t frequ ency of: •
1.4 dents/km, of which ...
• 0.3 dents/km are >2% pipe diameter in depth
•
Most of these dents were in the botto m (bet ween 4 and 8 o'clock) of the pipeline
•
The deeper dents were in the bottom of the pipe (33% of bottom-of-the - line dents, wer e >25mm in depth , ag ainst 6% of dents in the top-of-the-pipe (between 8 and 4 o'clock)
•
The re were no trends between pipe diameter (D) and dent frequency, pipe grade or age.
•
There were m ore dents and dee per den ts in pipe of high 011 ratio (tewan thickness), which are more flexible and less resistant 10 denting.
•
The met al loss pigs repo rted no weld or defect in 94% of the ir reported dents, but noted 2 .8% had metal loss defects (most in the bottom of the pipe), 1.8% were associated with the longitudinal weld, and 1.5% associated with the girth welds
C P..,.".n 2006 R..61'
s
"
3
PLAIN, SMOOTH DENTS '
--'.--'--_.-'' _,-,~""'_,,""'aI_
A ........ . . . _
__
. . . . . ......
..... _ _..-.. .. _ _
'1 6J ""_~
•
DENTS IN OPERATIONAL PIPELINES: Example
,
4
PLAIN DENTS - Depth and shape •
The DENT DEPTH is the most significant factor affecti ng the burst strength and the fatigue strength of a plain dent.
•
The SHAPE (length and width) of the dent does affect the stress and strain distribution in the den t, and the geometric stiffness of the dent , • bullhese effects do not appear to be as impo rtant as the dent depth
Width
----+ --
Length
-~_
.
._tt
PLAI N DENTS: Dimensions
= = = = O_;!l.IOII _'
dent depth pipe wall thickness pipe radius pipe diameter tz
6
BURST STRENGTH OF PLAIN DENTS •
Plain dents do not significan tly reduce the burst strength of pipe.
•
The effect of a plain dent is to introduce high loca lised stresses, to ca use yielding in the pipe material and wall thinning in the dented area. • The high stresses and strains caused by the dent are accommodated by the ductility of the pipe .
BURST STRENGTH OF PLAIN DENTS •
Full scale lests have connrmeo that plain dents do not generally affect burst strengths of pipe lines: • On pressurisalion the dent attempts to move outw ard, allowing the pipe to regain its original circu lar shape , • Provided that nothing restr icts the movement or acts as a stress concentration (e.g. a gouge or a kink), then the den t will not reduce the burst strength of the pipe,
7
BURST STRENGTH OF PLAIN DENTS: Depth Limits •
Empirical limits for plain dents under static internal pressure loading have been derived from extensive full scale testing. • It should be noted that all of the dent depths in the full scale tests were measured at zero pressure. • Therefore the empiri ca l limits may need 10 be corrected for spring bac k if applied to dents measured in pressurised pipe.
BURST TESTS ON PLAIN DENTS - Test Data
i
•
"" 14 0
~ ....~
..• ..........
•
*. •
•••• • • •
•
IT
I ~
1,1
• ... FAILED IN DENT .. FAILED IN DENT
... FAILED IN DENT
\
•j
FAI L ED IN DENT .
.,
• Ban. 11981 1 • Bnb$I'l Gas (1982, 1983) • CANMEr (1979, 1982) ... ONV (I982.2000) SES(1997)
20
*
e
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o.t
0.15
oz
oenc D8p1h1P1p"
""....c..
D1•
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(HID)
""
0 45
te
8
• Full scale tests by British Gas, Battelle and others, indicate that plain de nts of less than 8.0% of the pipe diameter (measured at pressure) do not significantly effect the burst stre ngth of pipe . • In the Brit ish Gas tests, plain dents of up to 24.0% (m easured at zero pressure) did not significan tly reduce the burst strength. • Note that this depth (8% ) is for BURST (static loading) strength and does not include allowance for FATIGUE loading ( see later). • If your pipeline has fatigue loading (e .g. pressure cyc ling), this 'acceptable' 8% dent size may be decreased .
e p ",, ~ 2006 R~6I l
"
BURST STRENGTH OF PLAI N DENTS: Notes o n Dent Depth Lim its • It sho uld be noted that a de nt of depth 8.0% is a technica l limit • this de pth may restr ict product flow , prevent the passage of pigs along the pipeline • The high strains asso ciated with deep dents may disband coatings
• Because of this, dent limits in pipe lines have tradit ionally bee n restricted to 6% diame ter"
~
..",,--_ ..,............... ". ""_,__" ... _ .............,_. ..._ ,
_
~. _,. -.T
"" ... _
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_ ·o"_"""""_' '''''' . ' __ ''' '''''''_o-..· ........'.... ~,,,"""'o.-_"'
''''' .,, ,''
"
9
BURST STRENGTH OF PLAIN DENTS: Notes on Dent Depth Limits • NOTE: Full scale tests on plain dents on welds and dents containing defects have demon strated very low burst pressures (see later) • Dented seam welds have shown failure stresses as low as 7% SMYS
• NOTE : A recent field survey" of dents detected by geometry pigs in a 16" pipeline stated that more than half the dents contained gouges
Sf
~
I]
>50% contained gouges
rs
C Po n..,." :/OOl,l R ",, & l
BURST STRENGTH OF PLAIN DENTS: Estimating , Strains in Dents (ASME B31.8 App R)
I
We can also 'accept' dents based on the strain caused by them (ASME B31.8App R· ·) : Bend ing strain (eire. direction), Cj
:::
WI{11"') - (1IR, )] Bending strain (long. direction). 82 :::
-V2R 2 Extensional strai n (long . direction). 83 :::
[1 f2).[d/Lj2
(
SeeASME 63 1.8 for summation of all these strains
Ro ::: nominal pipe outsid e diameterl2 .,,"" " ' " '' '''' L ::: dent lengt h. d = dent depth,! ::: pipe wall Ihickness J "--"""""+""'~---'
I R,
Th e ASME strain limit in a cent is 6% This is based on: A SME 8 31 allows strains of up to 3% in field bending: and the chance of crac king or puncture of linepipe increases after 12% . Th erefore. 6% was selected byAS ME,
... '"
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10
FATIGUE STRENGTH OF PLAIN DENTS • A dent in a pipel ine causes a high localised stress and strain co ncentra tion.
Pre ssure
Time
• Under cyclic pressu re loading there will be large cyclic stress and strains localised in the dent.
"'- - -
• Cyclic pressure fatigue tests on plain dents in pipes indicate that plain dents reduce the fatigue life compared to plain circular pipe .
Cl_~_ '
"
FATIGUE STRENGTH OF PLAIN DENTS - Depth and Mean Stress • Eff ect of de nt depth: • The greater the dent depth the shorter the fatigue rife.
.
• Effect of mean stress: • In some of the tests in which the maximum stress was high, the de nt was pushed out during the first cycle, and the pipe regained its cir cular sha pe.
Stress
• Consequently , no fatigue failure occurred.
• The fatigue life of a plain dent is dependent on the me an stress level
r f' ~Cl ic ~tresf
\ VI
Mean Stress
Time
• higher mean stresses promote re-rounding of the pipe .
C_XIOI_.
n
tt
FATIGUE STRENGTH OF PLAIN DENTS - Length •
Effect of dent length: • In long dents, fatigu e cracking is long itud inally or ientated and usu ally occurs in the cen tre of the den t (but often slightly displaced to one end). •
In short den ts, fatigu e cracking usually occurs around the fla nks of the dent.
• The different behaviour is due to the fact that the location of the peak stresses and strains is different in a short dent and a lon g dent.
C Pon""",, 2006 Il... 611
FATIGUE STRENGTH OF PLAIN DENTS· Multiples •
Multiple dents - dents overlapping can lead to fatigue cracks in the 'saddle' region between the dents, and decreased fatigue life
• see AP I 1160, App. A
'Saddle'
I
12
FATIGUE STRENGTH OF PLAIN DENTS - Models
•
The European Pipeline Research Group (EPRG) has developed an empirical model for predicting the fatigue life of plain dent. • It ca lculates the fatigue life of a plain dent using the fatig ue life of plai n pipe (from S·N curves), mod ified for the stress concen tration due 10 the dent.
•
A semi -em pirica l model fo r assessing the fatig ue life of a plain dent has been developed by Fowler at SES (for the AGA) • S· N curves modified for the stress conce ntration due to the dent are used.
!
t-------.
Fatigue Failure ~./ n .. ~" . . . lh o " ' ;9"0 ,. ,, " ,. 10M
! 1
No Fatigue
cl_1OOlI_'
Fai:~
. . . . -. . . C"a.. . .......... ~
FATIGUE STRENGTH OF PLAIN DENTS - SES Model •
The SES fatigue mod el is based on an S-N curve, modified for the stress co ncentration due to the dent.
•
A 'stress intensifi cation factor' has been derived from FE analysis to > account for the stress con centration due to the dent. • It is a function of the diam eter to wall thickness ratio (O/t), the ratio of the dent dep th to nomin al diameter, and the ave rage pressure.
N = 2 .0X I 0 6( [ I'>. CY.' ]1'>. 1 I'>.p P 11400
)-3.74
N
=
predicted fatig ue life of plain dent
l:J
=
'stress intensifica lion factor' (from Tables in original reference ). cyclic press ure, psi
=
[EQUaOOn given above is baMid on APl-RP2A Cu....e X1
13
FATIGUE STRENGTH OF PLAIN DENTS - SES Model versus Test Data PREDICTED
F TIGUE LIFE 1000000
UNCONSERIJATIVE
Note Scatter
., 1000 1 - 1 100 L-Ll.JJ.J.:
1000
10000
100000
1000000
Number of Cycles
10000000
A TUAL F T G
F
EPRG PLAIN DENT FATIGUE MODEL •
The emp irica l EPRG fatigue model is base d on an $-N curve , modified for the
stress concentration due 10 the dent •
The S-N curve is for long itudinal submerged arc welded pipe (taken fro m DIN 24 13).
•
The stress concentra tion factor for the dent has been derived by comparison with EPRG and Brit ish Gas lest data .
•
It is a fun ction of the d iameter to wal1lh ickness rat io. and the dent depth .
•
The equat ion for the fatigue life (in SI units) is:
COIID£R.I.. 01_ "' E_ _ . T_ _ .... on""" "..
... _oI"' __ .."..EF'RGIPI
Cl'AT " ~ , P : EP1lG _."" ~
_~
UK.
...... ,...
14
EPRG PLAIN DENT FATIGUE MODEL (contd.) •
The model is based on tests in which the damage was introduced at zero pressure; the den t depth is tha t after spring back, measured at zero pressure. Therefore , a correction must be m ade for den ts introduced at pressure and measured at pressu re.
•
The model does not predict the expe rime ntal observed effect of mean pressure on the fatigue life of a plain dent.
•
The model is nol directly applicable to loadings giving rise to high strain-low cycle fatigue behaviour, Le. reverse plastici ty .
t
pipe wall thickness, mm outside diameter of pipe . rom dent depth measured at zero pressure, mm predicted fatigue life of plain dent ratio of minimum stress in stress cycle to maximum stress in stress cycle (= u"../u"",;r) ultimate tensi le strength, Nmm-2 equivalent cyclic hoop stress range corresponding to R O. Nmms
o
Ho
N R O'u
=
2aA 0"'-- 2001_ '
29
FATIGUE FAILURE AT OF A DENT: Case Study 00
•
• • • • •
•
".
Product pipeline. Built in 1980 Diameter = 12", wall thickness = 0.25 ", Max pr essure = 1100psi , Mi nim um pressu re = 400psi, Grade = X52 . 2 cycles of 700psi/day
Dented due to tree falling on it. • Den t depth = 1", De nt length =
T
I-
I-
--. _ .
• No surfac e damage.
•
Stress analysis of dent concluded high strains are in dent (strains<0.021).
•
Failed in 2001. as a rupture. three months after dama ged introduced. •
J_
--
-.
~_
._
_
- ~_
.....
--
Calculated fatigue life usi ng EPRG model is 6 months
"
15
FATIGUE STRENGTH OF PLAIN DENTS - ASME 831.85 Guidance" •
Tests have shown that de nts of (residual) depth 2% pipe dia meter or less: • have long fatigu e lives (100 ,0000- 1,000,000 cycles)
• even at high cyclic stress levels (36-72% SMYS ). • This fatig ue life woul d be con sidered 'infinite' in a ga s pipeli ne
•
A fatigue failure of a shall ow den t in a gas pipeline has never been reported in the USA*
•
This ma y not be the case in liqu id lines tha t hav e different. more severe cyclic stressing
•
There have been reports of failures of rock de nts in liquid lines , a few yea rs afte r the rock has been rem oved
·.J_ ~
_"' _c......... _ BJ' I"" __.....
Gas
C:> 2%D
'\
LIqUId? . -
.'
_"'_~ ·,
..,_
Od2002. .-. _ '~ _11' 1X1
FATIGUE STRENGTH OF PLAIN DENTS - Case Study .24~ .
0.25", crude oil line
aconeuucted in 1975. Pressure = 606 psi
f €fE«
_In 1997. a contractor's magnetic flux standard ... resolution inllne inspection tool was run 1997
_ Excavations were made at locations alo ng the pipe line where the inspection 1001 indicated significa nt ano malies. _ At the site where the pipeline ruptured, the 1997 inspec tion data showed an anomaly that the contractor had interprel ed as a "de nt." _T he pipe line had not been excavated at this loca tion beca use the dent did not appea r to meet the repai r criteria being used at the time. _T he repair criteria used required that, for a dent to be repai red , it had to be deeper tha n 2 perce nt of the outside diamet er of the pipe.
_Failed in 2000. $7million damage/clean up costs
16
FATIGUE STRENGTH OF PLAIN DENTS - Case Study (cont) _ The dent was consistent with contact with a hard object _no hard object likely to have caused it (such as a rock) was found
_ The rupture was on the botto m of the pipe. e'rrans-qraoutar cracks: appearance typical of fatigue progression we re present. • Maximum depth of the cracks was 90-95% of the pipe wa ll thickness .Primary and secondary origin areas of fatigue cracking were found at the edges of a dent, in the pipe wall. Secondary cracks were in the vicinity of the two origin areas
_N TSB Conclusion: pipe failed due to fatigue cracki ng _Due to a dent in the pipe that was subjected to high local stresses from fluctuating pressures within the pipe.
Soo N' SO R_
""",,- P. .
~H) 2
""'-
_
DENTS WITH WELDS
•
17
DENTS WITH WELDS •
Full scale test s have demonstrated that den ted seam weld s can exhibit very low bur st pressures • Fail ure stresses as low as 7% S MYS have been reported
•
Similarly, dented girt h welds would be expected to exh ibit very low burst pressures • The low burs t pressures are caused by crackin g in the weld as a result of the large stress and
strains associated with the denting process. •
T he fatigue life of a dent contain ing a weld can be considerab ly lower tha n the fatig ue life of an equivalent plain dent
•
See Pipeline Rese arch Council Internationa l Rep ort PR ·2 18·9822. 'Guidelines for the Asse ssments of Dents on Welds'
_ I~
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-
I~ ~
'\
[Q I
DENTS WITH WELDS - ASME 831.85 Guidance ' •
Tests on low frequ ency ERW and DSAW we lds in dents, and dee p dents on girth welds have shown low fatigue lives.
~
!It
~
IiiIJ
• Genera lly, den ts on girth welds or ERW , or DSAW welds have fati gue lives of about 20% that of a similar plain de nt with no weld.
•
O ld weld s suc h as acetylene we lds or severely flawed arc weld s m ay ha ve poor fatig ue lives .
•
If the longitudinal seam or girth weld is good qua lity. ductile and and fre e from major defects (e.g. the girth weld is to API 1104 ), the fatigue life can be good : • Some tests on (the better quality) high frequency ERW we lds in dents have shown good fatigu e lives. • Wo rk in me '90s for OPS in the USA also supported the view that shallow roc k dents on girth welds in gas lines were not a major prob lem
0_
2OOlI _ '
1_..
... _
I I_.. _
e.-.. _II3'.... _
.... _d
.... _
,. ~ O
18
DENTS WITH WELDS: General Guidance in USA •
API 1160 and ASME 831 .88 ha ve differing guidance
1~~3~~::~~~
on dents affecting lon gitudinal and girth welds: • API 1160 req uires dents affecting welds to be 'reported and mit igated' within 6 months; • ASME 8 31.8 infers that dents affecting we lds a re insignificant if the y are s2% pipe diameter in depth. •
The USA's Pipe line Safety Reg ulati ons for gas and liquid lines (CFR 192 and 195 ) both infer that dents of depth :52% pipe d iam eter contain ing a weld are insig nifi cant.
•
All these guide lines wou ld require that the we ld is good q uality (in particu lar. ductile) and free from defec ts (e·9· acceptable to API 1104 ), an d with the pipe coa ting unaffected by the denting .
O~:lOOll_'
..., _•• _ .._ _
o-... _
IJ' I"'
"_~."'
I
S2%D
_
e:...-0
'CONSTRAINED' DENTS
•
19
UNCONSTRAINED AND CONSTRAINED DENTS •
Recent work. spo nsored by A PI (and pub lished as A PI 1156), has looked at the behaviour of const rained and unconstrained dents .
NO CONSTRAI NT
-----------
• An unconstrained dent is free to rebo und elastically when the indenter is removed and free to reround as the pressure is increased . • A constrained dent is one that is not free to rer ound or rebo und (be cause the indenter is not removed). • A rock dent is an example of a constrained dent.
•
Constrained dents and smooth unconstrained dents do not significantly reduce the burst strength of the pipe. CONSTRAIN T
UNCONSTRAINED AND CONSTRAINED DENTS •
•
The most likely failure mode of a constrained dent is by puncture, but only if the indenter (e.g. a rock) is suffic iently hard and sharp , and the bearing load is high (and increasin g). The fatigue strength of a const rained dent is greater than that of an equ ivalent unconstrained dent.
~_
• In the API study , no fatigue related failure of the sharp constrained dents was produced . _
Fat igue cracks in constrai ned d ents in itiated at th e in si de s urfa ce .
_
Fat ig ue c racks in unconstrained de nts in iti at ed at the o utside s urface
20
SIGNIFICANCE OF ROCK DENTS • In relat ively thin walled pipe, most dents will reround to less than 5% diameter when the pressure is increased to 72 % SMYS . • At 90% SMYS (e .q . following a hyd ratest), the dent is likel y to be less than 2% diameter.
• Consequen tly, a dent bigger than 5% diameter in the bottom of the pip e is prob abl y a rock dent.
• Rock dents are very com mon, but of little consequence per S8 . • T he den t is constraine d, the weight of the pipeline and the presence of the rock prevents the dent from refounding.
..
SIGNIFICANCE OF ROCK DENTS •
USA experience" is that rock dents are rarely associated with surface da mage .
•
• However they can cause failure (usually a leak); the pipe can be punctured (if the rock is sharp and bearing load is high ), or any asso ciated coal ing damage can lead to a corrosion failure .
•
If the constrai ning obj ect (the rock ) is removed the n the constrained dent will become uncon strained.
•
Rock dents are l i ke ty"t:,:, o-,be ::.:a~t~th ~e=bottom of a pipe". -
•
Mecha nical damage is likely to be at the to p.
•
A de nt reported as greate r than 5% dia meter is pro bably a constrained roc k de nt, or a bu ckle.
-,>.J·""-/
...
~"'--._"""'-~----e......... _ "'_ ._"..... ~"""-_""_,,,,,,,,_"ipo-~
-
"
21
SIGNIFICANCE OF ROCK DENTS - Multiple Dents
..
-""""",,-_. -,--,..----'"-~~~--~~--~-,----~
__
•
~~~.,........-""~~~_.~-"~
z'·~.·.:;,,::.~'i.','~"'" -".F::7_:::;;';~:~~",>; ~~,if~
Note that multiple restrained dents (e .g. rock dents) in liquid lines may be a problem" : • This is because the 'saddle' area between the dents is not restrained , and can move and cause fatigue fai lures in lines thai are heavily fatigued , i.e. some liquid lines.
• Guidelines are:
• if th e d ent ce ntres are sep arat ed by les s than one pipe di am et er, th ey w ill need t o be in ve stigat ed • Investigation will involve remova l of the rock (l.e. remova l of constraint) and th is wi ll likely lead to a repair
•
Note that no reports of fatigue failure s in mul tiple den ts in ga s lines have been reported' .
o_xa_
...J _•• _
.. _O'-..._
.., I ....
..
_
. .. _
~
__"">OIll.~_""ClQOl.;lJ'U
SIGNIFICANCE OF ROCK DENTS - with corrosion •
Tests on corrosion in rock dents have shown the dent and corrosion to have high burst strength due to tile dent preventing the corrosion bulging. • The failure pressure of this corrosion wa s conservauveiv predicted by RSTREN G
.<•k•• . . .~ ... ,. .
""
•
. ~
,
.
-
-
';
-
'- . ~
• Therefore , it is possible to assess corrosion in a restrained dent by using corrosion equatio ns, and igno ring the oent' .
•
Note that corrosion protection will still be needed around the rock dent to prevent further corrosion and possible SCC.
•
Environmentally assisted crack ing has been observed in den ts in liquid lines"
. J_..
" _d_e.-..
_ e . ) I . I ... _
.... _ d _ ~ ·,
_ _C
..
22
SIGNIFICANCE OF ROCK DENTS· API 1156 •
API 1156 concludes that unconstraine d den ts of 2% pipe dia meter, ha ve good burst and fa tigue strength.
• The presence of a stress raiser, or a weld in the de nt, reduces the fatigue life. •
API 1156 concludes that constrained (rock) dents ha ve good burst and fatigu e properties, and suggest that removing the rock is not , generally, a good idea . • "Constrained dents less than 6 perce nt in depth are not a problem , unless they involve a sha rp obj ect whi ch m ight cau se a puncture or the y interfer e with operations such as pigging .-
ROCK DENTS or MECHANICAL DAMAGE '? •
u.
MECH A NICAL DAMA GE:
• Shape : long & narrow aspe ct ratio, or several paralle l or adjacent sim ilar feature s, crea selike shape; •
Clock posit ion: most encroachment impa cts are in the top half of the pipe ;
• The physica l lay of the pipe line - an indicated "sag bend" where the line crosses nat terrain may represen t creases fro m backhoe scrapes being confused for mild ripples in a field ben d; •
•
Pro ximity to above-g rouncl feat ures where earthmoving ma y occu r: e.q. nea rby road cro ssin gs or recent construc tion
ROCK DENTS • Shape: rounded profi le rathe r than long and narrow; • Clock position: mos t rock-induced dam age occurs on the lower half of the pipe; • Depth: 2% of the 0 0 or g reater; • Ext ent: sig nifICant amoun ts of ovality or indentation extending ove r several feet of pipe . ""
_
~"-
"
C
'_ _ ""_'''' '
'_
"
23
POSITION OF DENT: API 1160' for Liquid lines AC TION:
DENT @TOP
immediate
- de nts with any indicated meta l
concern
loss
within 6 months
- dent depth >2 % diameter - dents that affects pipe curvature at a girth we ld Of a long itudinal seam we ld
ACT ION :
DENT@BonOM
within 6 months
• dent depth >6 % diameter
•
- dents with meta l loss
f
~
_
"
30 GayS. l
..._
l
alI'ICMn" is
....... lmes""voo_ " ..
200' _ _
T
_Ie
I
-""
4 o 'clo c k
SODOM l
Note :
·"*""__ s , - _... _
8 o'c lo ck
_
- dents that affects pipe curvature at a girth weld or a long itudinal seam weld
...(_
DENTS AND GOUGES
•
24
DENTS AND GOUGES • When a pipeline is impacted, it can be both dented and gouged . • A dent under internal pressure causes high stresses and strains. • In the case of a plain dent, these stress and strain concentrations are acco mmoda ted by th e du cti lity of the fine pipe .
.,
DENTS AND GOUGES •
The stress concentration and the large strains caus ed as a dent moves outwards under the
action of the internal pressure caus es ductile tearing of any
defect within the dent •
The te aring goes through the rem aini ng ligament.
Defe ct
I Teari ng
25
DENTS AND GOUGES· Dimensions
»>: \/-....---.
.'
.:
:
.......
,, '' :,, ' , ,, '' ,, '' ,, ' ' ,, ' ' ,, ' ' ,, ' '
-'"
d
.
.: ... .' .-'
" ---i--_'" "
=
I
=
D
=
,
t
.de fect dep th pip e wa ll thickness pipe diameter
H
R
= =
dent dep th pipe radius
DENTS AND GOUGES · Tests • De nts co mbined with defects ca n fail at very low pressures. • The struct ure comprising the dent and the defect is complex and unstable. • Dents com bined with defects are a very seve re form of damage. • Full scale tests indicate that dents combined with defects can reco rd very low burst pressures and short fatigue lives
26
DENTS AND GOUGES: Full ScaleTests
_ _ dCMO
DENTS AND GOUGES· Model for Burst Strength • British Gas developed a fracture model for predicting the failure stress of a combined dent and gouge . • The fracture mode l is based on exten sive testing
•
• The model gives a best estimate of the failure stress of a combined dent and gouge defect, not a conservative estimate. • The scatt er in its predictions (see later slide) indicate it to be more of a research tool than a practical model, • Its use in the field is not recommended - without expert help.
..., _ _
••_
.. _ e-..........,_ . ... _""'nJl-17,n
• _ _ ... _
~OOIl2."-
27
DENTS AND GOUGES - Model for Burst Strength
~=;cos-l[e,p-{~[Y,(l -~)+ y,(10,27~)r exfn(C~,-KI J}]
a=I.l5<7,(1-1) Y, LIZ -0 23(7) IO.{ 7)' - ZL7( 7)' 30.4 (7)' Y, 1.1 2-L39(;) 7.3Z(;)' -13.l(;Y 1 4.0(;r =
+
+
=
+
+
K, = 1.9
K, = 05 7 hoop stress ~t failure (Ib/li,,:') plastic colla pse stress of infinitely long goug e (lbflin 2) yiel d strengt h (Ibllin') fracture Are a of Charpy (0.083 in' for a 2J3 Charpy specimen) Young"s Modu lus (30,000,000 Ibf/i,,:') 2/3 Charpy toughn ess (ftlbf) ma xim um or averag e dep th of part wa ll defed (in) dent dep th measured at zero pressu re (in) pipe wa il lh ickness (in) outsid e radius of pipe (in)
DENTS AND GOUGES· Test Data versus Model ·--·-~--·1
PREDICTED
" '•-
• E. lI.... Ga>T.." C Ba'''''' I1''' I ' ' ''''
• T<,,,,,,G',,
" . "ii•••
0 ""'_
CANMET ' .,.. . Sf S l
V..." T....
O .C O N SER VATIVE
a
UNCONSE RVATlVE
~ •
. ..
•
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~
• • • • .a • 'a u, -e • B 0 •
•
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o
-e
-
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n ooOO oo OO
,·.'
•
•
•
....."....
•
..,
.'
- . 1"
• •
-
•
J ••
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e.
-,
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•
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~
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c
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•c
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100
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, .,
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Meas ured Fail ur e St ressfYield St rength, %
MEASURED O P_
2006 Re.6I'
28
DENTS AND GOUGES· Fatigue Strength •
Full scale tests have shown that dents combi ned with defects genera lly have very low fatigue lives.
•
The fatigue life of a dent containing a gouge is difficult to predict. • Full scale tests indicate that the fatigue life of a combined dent and gouge can be of the order of between ten and one hundred times less than the fatigue life of an equiva lent plain den t. • In some cases even shorte r fatigue lives have been observed during testing,
•
Wo rk by the Ame rica n Gas Association (AGA) have shown that the presence of a gouge as small as 5% of the wall thickness can reduce the fatigue life of a smooth dent by a factor of 40.
r::-----:----::=-----::::-----, En mples of Effect of Damage on Fati gu e U fe Fa tigue life Damage
Dent Dent & Gouge C _ _ 2alII-.
1000 -1 ,000,000 O· -30,000
"
DRESSING DEFECTS IN DENTS
se
29
DRESSING DEFECTS IN DENTS · •
It is possible to restore the strength of a dent containing damage by grinding (dressing) the dam age.
• ASM E 831.8: Grinding up to: • depths of 10% 1, to any length, and • limited lengths up 10 40% t
r;;;;;1O;%:;1=r.;;;;;:;l==~~
"
4O%t
iii
_
~
~~
• Has been shown to be safe. • A further limit of dent depths less than 4% has been stipulated for these grinding repairs". • A formul a used for calculating acceptable grind length s is given in the publication below*, AS ME 8 31.8 & CSA Z662 Examples of Effect of Grinding Damage on Fatigue Life Damage Fatigue li fe 0 - - 100 ,000 Dent & Gouge
C_20J5_,_.. _..
...
De nt & Grin d _ ~ . _
""..... '--""''''''.,.,.,
. __·.,
- 1000 - - 100,000
_
ss
DRESSING DEFECTS IN DENTS - Safety •
Note that any work on a pipeline, including grind ing is hazardous, and that a dent may become unstable as the grinding progresse s.
•
Ensure pressure reductions and safe working practices if grindi ng a defect on a pipeline .
30
SUMMARY· Fatigue strength of plain notches, plain dents and dents and defects
•• DENT & NOTCH Examp les o f Effect of Dam age on Fa tigu e Life
Damage Gouge Dent
••
Denl & Weld Dent & Gouge
"
,. (Equivalent) Number of Cycles
"
OTHER GEOMETRIC DEFECTS IN PIPELI NES
31
LARGE DEFORMATION, KINKS •
Pipelines can undergo extensive deformation - e.q. an anchor dragging an underwater pipeline.
•
A kin ked dent is a dent whic h contains rapid changes in contour, i.e. it is grossly distorted.
• These large deformations need to be assessed using structural analysi s
• Kinked den ts would be expected 10 have very low burst pressures and short fatigue lives.
ea
WRINKLES, RIPPLES, BUCKLES •
Somet imes pipelines con tain w rin kles or rippl es (local deformation with outward bulging or inward symmetry) or bu ckles (a wrinkle/ripple that has large deformation in the pipe) • AP I 1160 defines a buckl e as deformation I:::::;:~":"~!:':~! with amplitude >lio (25mm) • API 1163 considers a wri nkle as a smooth localised bulge on the outs ide wall of a pipeline with a height greater than one wa ll th ickness (I) • API 1163 con siders a ripple as a smooth locali sed bulge on the outside wall of a pipeline with a height no greater than I
o
0_ 2OOlI_'
32
WRINKLES, RIPPLES, BUCKLES •
A wrinkle bend is a field bend with smooth loca lised bulges on the inner radiu s
• They are no longer allowed in high stressed pipelines • Some old failures in wrinkle bends thought to have been cause d by ground temperature and line pressure
()
8'......·. (.)
~
RIPPLES
•
Rece nt" recommendations on rtpptes in field bends:
0:== 8 ::=0
• Gas Lines: Sha llow ripples having crest-to-troug h dimens ions
• up 10 1% pipe outside diameter (00) for gas pipeli nes operating at stress levels>
47,000 Ibflin' ,
C
Gas
1 to 2% OD
• increasing to 2% 00 for gas pipelines operating at < 37,000 Ibflinl
• Hazardous Liquid Lines: Shallow ripples having crest-to-trough dimensions • up to 0.5 % pipe 00 for hazardous liquid pipe lines operating at stress levels >
Liquid
0.5 to 2% OD
4 7,000 Ibmn' , • increasing 10 2% 00 for hazardous liquid pipelines operating at .c 20,000 Ibfli n2 . co _
200ll ... ..ell
-_. -.o J
_ ~"_"_.",-,,,,,,
_~
__ "_'''_',.
-""""-'''''''''''-'-''--'''''
ee
33
ASSESSING DENTS: Summary •
Plain Dents • No big problems under static loading
• Fatigue loading can be a problem, especially in liquid lines • U se EPRG or 'SES' mod el for fatigue
life
•
Dents on We lds • Low failure stress and short fatigue lives
•
Dent and Gouges • Very se vere damage and low failu re
stress es • Very sho rt fatigue life • EPRG mode l for bur st stre ngth, but inaccurate, probably better to repair
C_2006_ ---~ ._-----
.... ------~--
ADDITIONAL INFORMATION
0_20:15 _ _
ea
34
TEST DATA
es
FATIGUE RESISTANCE OF DENTS - Test Data
".
"[ ."
*U
E .!!! ••
[] ",_ T_. """"'ET _ ~
•
' _ <>- T."
•
. . .... T_
•
o SEU _
ri
. • I' •I •, • •• 8 I I a, 0·" . I .. • 11-· ~ I .... .1 -..- ..t.. • •• . •~: I I I • .. • •• I I II •• - ----
~
Ii
0
a::a ••
,
"..
i •
0
~
r:
•
(equivalent) Number of Cycles
"
35
BURST STRENGTH OF SMOOTH DENTS AND DENTS ON WELDS - Test Data 180
FAILURE STR ESS
I
160 ~ 140
~ 1 20 ~ ~
~
100
••
80
~
60
•
~
•
.'.,... ,''' '
. --DID ". NOT FAIL
.',
,
".'
•
....
.;... "
:
.•
I ""
•
" \ '\----_ '--"
,
, c
• ••
u,
40
VERY l OW FAILURE
•
20
STRESSES
•
oo "
0.1
0.05
0.15
0.2
0.25
0.3
0-35
0.4
0.45
Dent DepthIPipe Diameter (HID) . D ENT DEPTH . 0 __-
FATIGUE STRENGTH OF DENTS WITH WELDSTest Data
......"""' ......", .....,
o.
oENT ~ I
ea
oEPTH
I.
f-
on~"" _
~.11
i
.11
!
t. ,.
,
•
•• a.,. I
f .' 1.• I
, I
o.
••
"
•
VERY LO~~ u" FAT IGUE LIVES
•
C_2006_
If
' OIl
.----"""")
•
,. •
•
rtmr '
I.
•
, ,
• "
Itl1
' . 111'1
:
,- -
.
...':.", I ....t.: 11:n-
I ~ ... I J 1111111 I I I I Illill!. I
FAT IGUE LIFE za
36
FATIGUE STRENGTH OF SMOOTH DENTS CONTAINING GOUGES AND PLAIN DENTS l_
·· _
-.
..'P'RlI .....
III III f- UlI HHi-+tii1i'iii';=== -........::J.,....---., I.' 1--+t1+ttHH -- --~.
I J ~..
i
I
0'2
1000 -1 ,000,000
I . l• o.'"1--+-f+lBIiI-----:-'k
~ ~;
II.
' :': f-
VERYLOW FATIG' ,• ...--
L1~~
•
..
. ~~~
Examples of Effect of Damage on Fatigue life Damage Fatigue Life
I
I h· Iii
••-
I.
•
~I -
.
I~I~~::~:~:;, ;&~G~OU~, j f=++i1iiill--'-- - ---' 0- - 30 ,000
e
' i.. I:. -) . I ~ I~ .
'1:tl11iri- '
j'
:11 11ll
::'9
I
~J ~:+-+-l-+l1H I Ii.
4 . :;'I~· H. ++fl8
,
I FATIGUE LIF E'!
"
FATIGUE STRENGTH OF DENTS CONTAINING GRINDS: Test Data
l
rit! ~
(r
(J ...
' 0.""
o .... O . 1~ " '" 0 0 .15
•
• o.
• ... . 0."'"
~
. ... &- .
• ... _ 0 .:10 .. ... . O.3!I
'E .. ...
D ~~
_ 1M _on
~
""'0
• ... . 000
••
..
• OPoo_ ."
- *f
_.-
DEFECTS
AFTER
r
GRIND REPAIRS
Examples of Effect of Damage
0.-
J &
II
V
• •
I,•
;. -I'-+·
I
II
•
I
o n Fa tigu e Life Damage Fatigue Life 0 - - 100,000 Dent & Gouge - 1000 - - 100 ,000 Dent & Grind
•
I 1111111
~ DEFECTS II
IN DENT
I
- -
FATIGUE LIFE
"
37
FATIGUE OF PLAIN DENTS
API S·N CURVE USED IN SES MODEL
I l~YCLIC S.J:8 ESS, S
000
•
'"•m-
I
0
• ••
~
~
'00
1IIIIr
11' ,
111 11
I
1III1
,::m:
'"g
-
,
u
~
c
I
I
"'0000 0_ 2OOlI _ '
I I '00000
I '00000o '00000oo Number of Cyc les, N
I ~-
• I
I I I III II n rooocoocc
-ooccccooc
I FATIGUE LIFE, J,iJ te
38
FATIGUE OF PLAIN DENTS: EPRG Model versus T est Data
~
S ~u ;S
100000
10000
1;
._ .--a _
100
•
10 100
C_ 2COli _
T_
o CNA£T T_
1000
10000
100000
SES _
' 00000o
Number of Cycle~ ACTUAL FATIGUE LIFE
n
SPRING BACK AND REROUNDING OF DENTS
C_2O:l5_'
"
39
SPRING BACK AND REROUNDING • •
• •
•
Th e effect of intern al pressure is to stiffe n the pipe, increas ing the resistan ce to defo rmation. For the same ma xim um instantaneous dent de pth, the rem aining dent (after the removal of the indenter and spring back) when denting at zero pressure will be deeper than tile remaining dent when denting at pressu re. The dent depth changes as the internal pressure changes. In many of the full scale tests on plain dents and dents containing gouges, the dents were introduced at zero pressure • And the dent depth after spring back was also measured at zero pressure . • T he resultant empirical or semi-empirical models are, therefore. based on the dent depth measured at zero pressure. In pract ice , the majority of in-service damage (e.g . dents) wi ll be introd uced into pressur ised pipe, and the depth of the dent will be measured in the field whilst the pipe is pressurtsed .
O_2OOlI RO¥6'l
SPRING BACK AND REROUNDING •
s p ring back - (also referred to as 'rebounding') the reduction in dent depth due to elastic unloading that occ urs wh en the indenter is removed from the pipe
•
rero u nd lng - the cha nge in dent depth under internal pressure
•
The terminology of spring back and rerounding is adopted in order to distinguish between: • the change in dent depth associated with indentation and the removal of the indenter (spring back), and • the change in the depth of a pre-existing dent (i.e. after indentation and the removal of the indenter) under changing intern al pressure (rerou nding ).
ec
40
Spring Back and Rerounding, Dent Depth
,----,---.---...-"-----------------------------"' -"---'"' -- ,.--Hr
Ho
-
Hp
Hp> Ho >Hr Hp. ",stanlanloous (...... >:inun) llenI doplh IIC:t (1fIden' . in COI'IIact wiIh pipelin8) Hr _ _ depI'I.......,..;"g an.. ~ elf_ _ ( _ dolPh --..red at pt llSStlm)
Ho·
_~"""IfWIll.fIM.-.:;rot3I
d _
(deonIoe¢'..-nod 8\-., pressure)
.
0_2005_
Spring Back and Reround ing, Load and Displacement
Hp
di. I ~ H
ea
41
Spring Back and Rerounding, Internal Pressure and Dent Depth
~.:;;'.':;'.::::. """'-Joding
He
Hp
.. "", I ~ H
A REROUNDING CORRECTION FACTOR •
An empiri cal rerounding correction fac tor has been published by the EPRG .
1.43Hr = =
C_2OOll_1
dent depth measured at zero pressure dent depth measured at pressure
"""""'V""""""' .a-..• , ..
i
• CooNd>
_
' ..
...... ' _ _ ..
~_~
Sot
42
How to Assess Cracks
Penspen Integrity
Cl.... n.poon 2001 R...611
'_<--on_
_..,_ e-.>o.• _ .. _ _ "._"'><;<: .....,"'..-..........,......,....... w , = ,'''',..., e.-.o_ ... _
GIN•. " "
"""'__...'.•0'''''
... _ _ ""s<;<; .. _
~
<1$00
...... ' _ ....... _ _ " " . . .
"..
........_ .... ....
1
CRACKS IN WELDS OR FITTINGS
2
WELD/FITTING CRACKING .If you detect cracking in your pipeline, it is usually: _in weldments _in fittings, or
. will be environmentally created.
_Cracks in weldments (other than girth weld s). and in fittings, should be assessed using fracture mechanics methods, e.g.: Crack
_SS 7910 or _API 579
3
WELD/FITTING CRACKING: General methodology 1. DEF ECT F. UlIUOfTom 0 Hook C..,;k
1" s."mW. ld
2. FRACTURE ASS ESSMENT
.'
~~CT UR E
.. .. , ..
3. FATIGUE ASSESSMENT
_.,_. .... •
• •
••
U
••
'2
L".
,.
t. t.
U
.2
COLLAPSE
"~
~
log ,j}(
,
2
CORROSION - Some basics
C_2OOli_
5
CORROSION * - 'Galvanic', 'SRBs', 'Sweet', 'Sour',
'sec ' ENVIRONMEN T
ENVIRONMENT
Galvanic
Bacteria + sulphat es
External
r e-"" ] Erlema!' "
H2 S + wat er
9
I...( L""'"'''''.'
( -{
SOUR PRODUCT SWE ET PRODUCT
lote mal
I...(
E"""""
-------- CRACKING
<
..
-t
''''''''''''
<,
CO 2 + w ater ~
Internal
J lntemal"
' There are other cau ses of COO'OSIOO and <:racking in PIpelines · ' It is po$$ible . but ......... sual. to have(SSCC) <:racking on the external surface of the pipe . due to SRBs ••• ThIs crad li ng could be s e c (see laler) or HIC (see later)
s
3
EXTERNAL CORROSION· Galvanic Anode -lose electrons (corrodes) Cathode - gain electrons (prot ected ) (Molecular) Hydrogen (H2) cannot enter
"...
(Atom ic) Hydrogen (H' ) can enter steel
r
EXTERNAL/INTERNAL CORROSION - 'SRBs' • Most soils & wate r contain bacteria : they are usually not a corrosion prob lem . • The re are exceptions ... • Sulphate reducing bacteria (SR B): • bacteria that reduce suionates to sulfide. which reacts with hydrog en (produced by metabolic activities, or by cathodi c reaction of corrosion process) to form hydrogen sulphide (H 2S). • they create a corrosion process similar to the pitting of sour corrosion.
• SRBs need suionetesaround: no sutchatee. no prob lems.
e
4
EXTERNAL/INTERNAL CORROSION - 'SRBs' (cont.) • The SRBs grow in the absence of oxygen (anaerobic'), feeding on the fatty acids that may be present in produced water. • They only grow in the absence of oxygen , but oxygen does not kill them . • They produce large amounts of sulphide as they grow & it is this sulphide that causes corrosion.
• the corrosion is primarily in the base of the pipeline , local to the SRB colony. • SRBs cause localised corrosion, filled with black sulphide corrosion products
C P""'P"" 2006 Rev 6l1
9
T"" ,m'9"l"",, """.~ ."'9
EXTERNAL/INTERNAL CORROSION 'SRBs' (cont.) • Sulphate reducing bacteria (SRBs) are micro-organisms that chemically reduce sulphate ions in the water to sulphide . • These bacteria are 'non-pathogenic' (i.e. they are not capable of causing disease)
• The corrosion reaction involving HzS produces mono-atomic hydrogen (HO) at the corroding surface that should comb ine to form Hz gas, • but the presence of sulphide species retards or poisons this combination reaction so that the hydrogen diffuses into the steel
5
INTERNAL CORROSION AND CRACKING - 'Sweet'
and 'Sour'
11
INTERNAL CORROSION - 'Sweet' and 'Sour' •
'SOUR'::: 'Sour' gas/oil is high in hydrogen sulphides/sulphides
•
'SWEET'*::: 'Sweet' gas/oil is low in hydrogen sulphide/sulph ides.
SOUR
SWEET
H,S + Water
CO, + Wate r
•
Conp e on
' The process fe>r ",moving hydrogen sulph ide from sou, gas is coITJlllOflly refelled
to as 'sweetening' the ga s.
6
INTERNAL CORROSION - Sweet •
Sweet Corros ion is a corrosion process that reduces the pipe wall by the presence of wate r which is made acidic by the presence of carbon dioxide in the produ ct
SW EET
• It producesgeneral metalloss
CO 2 + Water
• Sweet corrosion will be the m ost likely
corrosion process, if there are low levels of hyd rogen sulp hid e in the prod uct
(cor-pslo
• As hydrogen sulphide levels increase, sulphide scales are formed on the metal
__) -
\:
surface and metal loss becomes localised and concen tra ted . • Iron sulph ide scal es predominate when the ratio of CO2:H2S is less than 500:1
"
INTERNAL CORROSION - Sour •
Sou r Corros ion is a corrosion process that reduces pipe wall by the presen ce of wat er and hydrogen sulphid e • The transition from SWEET to SOU R corrosio n will vary with product chemistry. ope rating co nditions . etc.. • NAC E" quote a level of HzS as 0.0035 bar (0.05psi) for this transition. • In sou r conditions there is the additional risk of hydrogen induced cracking and sulphide stress co rrosion cracking .
SO UR
•
H,S + Water
L(cra/ kng
)
"
7
INTERNAL CORROSION - Sour••• 1. Corrosion • In a sour environment we can have: • Pilling • From deposition of solid sul phides. or breakdown of the sul phide film that may form on the pipe ste el • This type of pitting may occur anywhere within the pipeline • Mosllikely at 6 o'clock position as this is where the sulphides are most like ly to
settle
e_2OOII_
15
INTERNAL CORROSION - Sour••• 2. SSCC
• •
In a sour environment we can have : Sulphide Stress Co rrosion Cracki ng (SSC C) • Can lake plac e when a susceptible metal is subject to a sour environment and level of stress (the stress may be re sidua l or applied ). • II is defined as brittle failure by cracking under the combined aclion of tensile stress and corrosion in the presence of water and hydrogen sulphide.
• The cracking is thought to be caused by the embriltlement of the metal by hydrogen.
-
~;r
O_2OOll_,
STRESS
H, O + H,S I H -+ H+.
• SSCC is found to attack higher strength materials (act ual tensile strength of :!:550MPa) • Hence , it is often associated with weld heat affected zones and cold wor1c.ed sections, v.t1ich tend to be stronger than the standard line pipe .
.•. . . .•.
•
we ld "-
SSfC
1- \ ;;L rs
8
INTERNAL CORROSION - Sour••• 2. SSCC • Few SSCC fa ilures have been reported in pipelines
Hydrogen cracking
• mosl are associated with hard spots.
• AS 2885.1 says that the susceptibility of stee ls to SSCC is indica ted by a hardness of more than 22 HRC (Hardness Rockwell C) • by limiting the hardness of the steel to this value, failure by SSCC is avoided
• NAC E MR0175 contains more information 0
_
produced by Itle cottOIion rNClion '" iron.usuaIIy-.t>one 10 bm ~, ill " . ~ at sulphide. toe hydrogen ~ t e I d i o n .' ~ I O _ . " . hydrogenllloms cduwno1l'e _ _ ~
_
~ lI""
_
rroIeculet..
"
1..... 'I:>a.'Ilon ........... ....--lObrm~gas
INTERNAL CORROSION - Sour••• 3 . HIC • In a sour environ ment we can have:
me
• Hydrogen Indu ced Cracking (HIC")
\\
• Hie is most likely to affe ct susceptible steels w here an
11"--.
iron sulphide film has developed and hydroge n is prese nt.
i
I
• It is not depend ent on stress .
• Most corrosion processesproduce H2 • Acid corros ion l akes place at the steel surf ace and hydrogen is evolved. • Atom ic hydrogen (hydrogen iOns) is absorbed into the stee l, then diffuses through the steel.
• The ions migrate into sates within the steel , such as void s or inclusions
t
)
• The ions combine to form hydrogen molecules: thes e molecules are too large to diffuse out of the steel • (up The10pressure builds uppsi)) and 18.6MPa (2700 cracks and blisters appea r
---~"'--
--
--_._.n...,_....-......__ . --
·W. __.HIC ...... _ d ....
...
_.,.~ .
18
9
INTERNAL CORROSION - Sour••• 3. HIC & Blisters •
HIe causes bliste rs in the pipe wall around ma nganese sulphide inclusions within the steel from ils manufacture. • Hence, Hie doe s not tend to be found at parti cular locations , such as weldments.
II Ie
HIe
If the Hie cannot propagate paral lel to the pipe surface, it may lin k up 'With cracks 00 adjacent, parallel ~anes
--~
AS 2885.1: The best approach to pre venting Hie in new pipelines is 10 use 'd ean' stee ls with modifi ed inclusion shape that do not have suita ble sites in their microstructure for hydrogen to accumul ate and ca use cracking. NACE TM0284 giv es guid ance and lests . Steels pass ing this test are ca lled 'HIC-resistant steels ... e . . . - _
_
ENVIRONMENTAL ASSISTED CRACKING (EAC): Assessment _Environmentally assis ted cracking can occ ur to both the internal and exte rnal surfaces of a pipeline _On the internal surface , we can have sulphide stress corros ion crac king (SSCC) , hyd rogen ind uced cracking (HIC) , etc.
Intern al Corrosion External
. On Ihe externa l surface our main problem is usually stress corrosion cracking (SCC)
_All these type of environmental cracking/co rrosion must be assessed using different methods to those describe previous ly, becau se these degradation mechanisms cause cracking, blistering, etc ..
_.-._- --
doe._
Hyn ~ a.d
__ cno<:l
_ca4
20
10
ENVIRONMENTAL CRACKING: Symptom - Cause •
Generally , we design aga inst corrosion cracki ng, •
•
Crack initiation is considered unacceptable. due to rapid subsequent propagatio n.
Consequently, cracking in pipe lines is not usu ally a defect assessment problem ; ' _....~ •
•
It is a symptom of something wrong - you need to isola te the cause & prevent/control it
Three fac tors contribu te 10this cracking: • Material microstructure • •
• •
Cracking
Environment Appl ied stress
W e solve the cracking problem by ch anging or controlling the se factors Therefore , avoidance of the prob lem may be achieved through • • •
malerial selection keeping the stress below lhe critical level for cracking Modifying lhe environme nt (this is only occas ionally possible) 21
ENVIRONMENTAL CRACKING: Solutions •
Internal cracking/blistering • • •
•
use steels with low levels (sulphu r & phosphorou s) of impurities mod ify environment by reducing hydrog en use surface coatings & inhibitors
Hydrogen embrittlemenl • • •
use lower strength (hardness) Of high resis tance alloys careful selec tion of materials of construction and plating system heat treatment to remove absorbed hydrogen
• see •
•
•
suass onenr.tr&d HIC is "" ""'1 of t",nsg"",,ufM
clH, -s<'crKI.oc.\;M... dftclion
See later
EVALUA TION OF H DAMAGE •
There are various laboratory (e.g. slow strain rate) tests
_ e - . .__
22
1\
INTERNAL ENVIRONMENTAL CRACKING· HIC and SSCC • SUMMARY
.orro ston of pipewall due I reaction and formation of iron su i hides and II
II
-
leI~:'::_.: -~" _. I
.._-:~
_~
.
H l can enter steel and cause damage and cmbriulcm cm.
SSl
weld '
~
Two types of crack ing ca n occur I
\\
[~
:--------r
§:' c,. . ;: -
Pipeline C ar ri es Sour Product with II ()
- ] [HYdmgon Induced Cracking 'HIO
I
H Ie IS stepwise cracking causcc oy t1 2 diffusing into the steel and enterin g voids
"n. ," .
.
C
'\
ISulph ide Stress Corrosion Cracking 'SSCO SSCC usually occurs in welds because it needs high stresses and hie h vicld strcneths/hardness
IThe solution is to select the correct (resistant) nine materials and cont rol nrodu ct oualitv
I
O_ 2OClII R ~ 1
23
ENVIRONMENTAL CRACKING - External "
.,,,f_
-W e can I>a>'lI " v""iely of ~ 0" !he " xlern,,1 01.. pipeline. '.g. hydn>Ql'l'l... &dar
"
12
ENVIRONMENTAL CRACKING - HACC ' ( • Cathodic protection systems protect the external surface of the pipeline from corrosion. • But if the potential is too negative, hydrogen can be evolved on the surface if the steel. • Even when CP levels are within recommended limits , hydrogen can be evolved from sma ll, narrow coali ng defects in lower resistivity soils in some situations
• Hard spots or mechanical dam age on a pipe 's surface will have high hardnesses • These areas can be attacked by the hydrogen from the CP and lead to 'hydrogen assisted cold cracking (HAeC )
O_
... _.
1llDIl _
25
ENVIRONMENTAL CRACKING - SCC •
A corrosive environme nt can crack mate rials • Stre ss corros ion cracking (SeC) is an example
• sec is not unusua l - many industries have sec • Nuclear reactor tubing can have sec •
•
Brass, Aluminium. Magnes ium can support
sec
In the 'old' gas industry, we sometimes had internal sec in our pipel ines from the 'town' ('coal') gas - - • The 'town gas ' was 35% CH4 • 45% H2 • 15% CO 2 , 5% CO , trace water and 0 2'
•
Pipeline steels and pipe welds can have external
see
Soil and water can be acidi c, neutral or alkaline. and the degree of acidity or alkalinity is measured on a pH scale that range s from 0 (most acidic ) to 14 (most alkaline). Tap waler is typicall y pH=7 , which is 'neutral'. 26
13
ENVIRONMENTAL CRACKING· SCC
(
•
The outside surface of the pipe line can be crac ked because of 'stress co rrosion'. It can affect both gas and liq uid lines.
• •
W hat is sec in pipelines? The sec is usually in clusters of cracks
•
The indi vidual crac ks ha ve typical lenqtr tdepth ratios of 4 to 8 • Cracks lend to interlin k 10form long , shallow flaws
• Fracture faces are covered in magnetite and carbonate films
- -- - . . --,-
~--
"
" ----_sec c or~~~
~
I . ....... -
ENVIRONMENTAL CRACKING· SCC
• sec is a corros ion process -
(
crac k-like defect s (rather that co rrosion pit s)
are formed. •
It need s three th ings to occur: • Mic ro structure - all line pipe is susc eptibl e (althoug h tensil e stre ngth may increase risk ) • Env iro nment - Any soil type can support sec, bul weVdry co nditions, or cond itions Ihat damage coating are more susceptible. Continually wet conditions (e.g . rivers ) have low incidence rate.
see
• Stress level - Risk of increases with stress MATERIAl although there is no lowe r thres hold . Loca l stress ( \. _ _ --::-.) ESS raisers (e .g. gouges) are conducive. Stress cycl ing \ J_ assists it breaks the protective oxide film at ENVI RONM ENT the crack tip and re-exposes the lip 10 the environment.
see -
•
T here are assessment methodologies evanebre' . but we usually try 10 avo id sec, or co ntrol it.
.... e'_'. _ _ ..._ _ ..._
_
~oec._
d
_ _ .'''' '''' '''''",,_
ae
14
ENVIRONMENTAL CRACKING · SCC
;;;;;
(I
:>
Material: Depends on microstructure, mposlffon. etc
~+-- En"ironment: corrosive. but might be very mild
.~2001_ '
29
ENVIRONMENTAL CRACKING - Stress Corrosion Cracking (SCC) i n Pipelines
• MATERIAL
=- -
STRE S
ENVIRONMENT
'Perh aps the hardest type o f defect to deal with Is s rress corrosion cracking... the main problem Is that no reliable model exis ts to define crack growth.'
-
PIP:ell ne Rules of Th um b Handbook. 4'" Ed . Gulf Pub lish ing . 1998 30
15
ENVIRONMENTAL CRACKING· SCC •
sec has been well known for many years in pipe line s
•
Has occurred in many types of line pipe (yield strengths of 241 MPa to 483 MPa )
•
The first documented case of sec causing a pipeline failure was the Natchitoche s, Louisiana . incid ent in the 1965. • This rupture was cau sed by high-pH sec & caused a gas rele ase & fire resulting in 17 fatalities
,--_._---ENVIRONMENTAL CRACKING· SCC •
The olde r type of stress corr osion cracking ('high ' pH· , or 'classical') only occ urs in a high (>9) pH (alkaline) environment
• It is associated with high temperatures. •
In recent years, there have been an increasing number of pipe line failures
sec.
• Caused by a different type of in environments with rela tively low pH ('near neutral' or 'non-classica l') of about 5.5-7.5.
31
() ~
,,
....
t /' , )
HighpH$CC
· pH is a measure of the acidity or alkalinity of an aqueous solution. It is defined as the negative log (base 10) of the hydrogen ion concentration. Water with a pH of 7 is neutral; lower pH levels indicate an increasing acidity, while pH levels above 7 indicate increasingly basic solu tions. 32
16
ENVIRONMENTAL CRACKING· SCC • Most see cracks are axial
sec
• When circumferential is found . it is in areas of loca l high stress concentration, e.g. a dent, or high external stresses, e.g. mountainous regions.
• Very few failures attributed to see around the world
• sec accounts for <2%* of total failures in USA gas lines . It accounts for 17% of total failures in Canada • Can occur in both liquid and gas lines
. . OPS ..
"$CC
_ ...........J_ ""' '''''''',
_
--
r>:_"--l. .....
>"'9""_""'''''''
_
33
ENVIRONMENTAL CRACKING· SCC
'T'·'T''''T''''T 7
8
' 10 810 910 20" 1 1m Il UIUtllllllllH III11Wlllllilull Single sec
...
,-
-~
--
..-' ;"
.. -
-;
---, sec colony
sec along t he fusion lin e of . .... T
-
_
"
.
~
- - . . . ' " " ". . _
<
_ u_ .."-.·.. __
_
_
a w eld ('toe crack') D_:IOOI~
---
.....
_<_<_.. __ _
t7
TYPES OF STRESS CORROSION CRACKING: High pH SCC
35
SCC: History of High pH •
HIGH pH
sec:
• The pri ncipal factor thai would is coatin g cause high pH condition.
sec
• T he first documented case of sec causing a pipeline failure was the Natchitoches, l ouisiana , incident in the mid 19605 (1965?) . • Occurred in USA , Italy, Australia. Iraq , Iran, Canada , Saudi Arabia , Pakistan. • Coa l tar and asphalt coatings sometimes susceptible (see API 1160. App A )
._--
• Mainly occ urs on gas lines, some 00 liquid lines _
_ .... ocrr .. _
-
.
.. occ
_
36
18
SCC: Factors Contributing to High pH a For high pH sec, high temperatures acce lerate cracking. a - 90 percent of the service failures and hyd rostatic retest failures occurred within 20 km of co mpressor station discharges where the temperatures and pressures are the highest.
a High pH cracking is axially-orien tated
_sec has occ urred at operating stresses from 58 to 80 pe rcent SMYS (average is 69 percent SMYS). a The coatin g types involved vary with ditch-a pplied coal tar and asphalt being the dominate coatings. • The environment detected at the pipe surface in high pH sec incidents is a mixtu re of carbonate and bicarbonate solution. a Often occu rs in bottom half (3 to 9 o'clock) of pipe 37
SCC: Environment ' of High pH ew hen pipe line stee l is exposed to the surrounding environment due to some form of coal ing failure, it is vulne rable to corrosion.
ea ecause soil corrosion is an electroc hemical reaction , CP is used to mitigate
.. corros ion by passing an electrical cu rrent through the soil thus g iving the pipe a cathodic potential.
_A conc entrated carbonate-bicarbonate (C03-HC0 3 ) solution has bee n identified as the most probable environment responsible for high-p H SCC. _This environment develops as a result of the interaction between hydroxyl ions produced by the cathode reaction and CO2 in the SOil generated by the decay of OI1lanicm atter.
_CP causes the pH of the elect rolyte beneath disbonded coa tings to increase . and the CO 2 read ily dissolves in the elevated pH electrolyte , resulting in the generation of the concen trated C0 3-HC0 3 electrolyte .
CO2 =HC03HCOi + C0 32- + W
A lk aline env irc nm e nt. ., O H - +
._-_. _"-0--",_..
et aco ratory tests on small specimens indicates t hat this form of SCC is tem perature sensitive and occurs more frequently at higher temperature locations (> 100°F). -.:o
. . . """_"""'.. _ . . _
~ .. _ _
38
19
SCC: Environment' of High pH . High pH cracks usually occur on gas lines ea pecmc potential range is -600 to -750mVo;s _Most failures have occ urred on pipes coaled with coal tar or asphalt. which is permeable, deg raded or disband ed
. High temperature allows faster crack growth rates, and coating damage is more likely at high temperatures
39
SCC: High pH Cracking in 'Intergranular' . High pH cracking is usually 'intergranular' and narrow . (Iow pH cracking is 'transqranutar'" and wider, with less branches) I..... rgran.u' Of TIlI"'lIr ~ nw, C.. e ~I"G
'-
~
,
~
r
:I~
StrKS COnoslon Cradling
-
K
~
'-
•
a Hlgh pH sec IS not usually associated with welds
20
scc: T ime for High pH SCC to Fail _ T he initial ave rage service life to first
sec incident in USA was
21 yea rs
with a m inimum time of 6 yea rs. Average ag e = 22 .9 years ;
0-6
7-12
13-18
19-24
25-30
Service Lif e to Fir st
Standard Dev. = 10.0 43 Incidents
31-36
37-42
43-48
49-54
55-00
sec, yea rs 41
scc: Time for High pH SCC to Fail _ T he time per iod to the initia l dependent on:
sec incident is
_ the deg radation of the coat ing _ the cathod ic potential range nec essary for cracking to occur _ the max imum operating temperatu re and _ tem perature va riations of the line seg ment, which infl uence the coat ing deg radation _ the soil stress imposed on the coating from the temperatur e changes _ chem ical activity of the env ironment _ the stress level and pressure fluctuat ions
21
scc: Needs stresses and strains see
_ The initiation and growth of requires the app lication of stresses that induce plastic level strains. _ Plastic level strains can occur from: _ the application of a number of pressure cycles , _ from the strain concentration associated with a dent, at the edge of a weld reinforcement, or _ from a pit on the pipe surface that has been produc ed by corrosion .
O_2OOI!i-"
FACTORS THAT INFLUENCE SCC '
see
-
Environment
Materials
I
I
-Soiltype
' pH -Pipe- to-sod potential -Redox' " potenti al ' Resistivity ·Temperature ' Carbon dioxide ' ?" O_2OOI!i-"
I
·Coating type ·Coating condi tio n -w eld type · Microstructure ' Inclusion type ' HAl versus body
·Drainage •Topography
' Pipe grade
-_..._d._·._ _ •
e...-~.
T
Stress · Hoop stress ' Geotech nical -Resjdual"?" ' Constru ction ·MiII ' Dents ' Gouges ' SCratches ' Cyclic component
A$LIE.1PC2OOI!i,~2OOI!i
- f""" cP -
bo_""_25_~SWVS
. 22
CONTROL OF High pH SCC - from PRCI . High pH sec can be both predicted and controlled by using a protocol developed by Pipeline Resea rch Council International (PRe l). The parameters are : ~ eating _ Coating, soil . and moisture,
'-/:::::::~""'~::3~=7"C;;;re
_ Maximum temperature.
_ Surface coating preparation,
. / '=
<,
• Hoop stress , _ Stress fluctuation level .
€ati~
_ Cathod ic potential level , and _ Initial test pressu re level.
_ Each of these parameters is given a 'weighting', and the likelihood of can be dete rmined for your pipeline . high pH
sec
e_2OOII_'
CONTROL OF High pH SCC - from ASME 831.8S (see also NACE RP0204 SCCDA) • ASM E 63 1.8 supplement gives an initial risk assessment protocol for high pH SCC' as follows: 1. Operating stress >60% SMYS >60% 2. Operating temperature >1000 F 3.
4. 5. •
0
Distance from com pressor station S 20mi les Age ~1 Oyears +AII coating systems other than FBE
S MY S
oabo
ears
If All of these are present then the pipe must be assessed for SCC . • In addition prior indications of SCC (inspections. failures) shou ld be eval uated unless conditions that led to them have been corrected . • Conventional survey techniques shou ld be used downstream of compressor stations to find areas of disbanded coating for excavation and inspection. _
-The saone cnwia · _ OOT _
used_ b _. m i l _ o n _pH sec on SCC _ _ 010» ....... .".
(~~)0llllIdbe
"""
23
CONTROL OF High pH SCC - Note ' on CP •
The CP current collecting on the pipe surface at d isbandments , in coojunction with dissolved CO 2 in the groundwater, generates the high-pH envi ronment.
sec
•
CP can also place the pipe-t o-soil potentia l in the po tential ran ge for cracking .
•
The potential rang e fo r cracki ng generally lies between the native potential of undergrou nd pipe lines and the poten tial associated with adeq uate protection (·850 mV CSE).
•
Based on field pH measurements of electrolytes associated with near neutra l-pH colo nies , it has been concluded thai this form of sec occurs in the abse nce of significant CP eithe r because of the presen ce of a shieldi ng coa ting or high-resistivity soils that limi t CP cu rrent 10 the pipe surface .
•
Based on the available labora tory and field data , it ca n be concluded that the polarized pipe- to-soil potential of pipeline segments that are potentially susceptible to hig h-pH sec should be maintai ned above (more nega tive than) -850 mV ees.
sec
0_2008_
---
--..._-,
_e-~_
...........
."
.'''''~_2I:IM'
..
_'' T_
TYPES OF STRESS CORROSION CRACKING: Low pH ('near neutral") SCC
"
24
SCC: H istory of Low pH ('near neutral') •
l OW pH sec: • Since 1972, Canadian standards have allowed pipelines 10 be operated at 80% of the hydrates! press ure • Thi s allows 80% S MYS operation in certain (remote) locations.
•
No major problems occurred un til 1985,
when stress corrosion cracking caused a number of failures.
• Of the 17 reported failures on Canadian pipeline s operating between 72 and 80 % SMYS, the major cause (7 cases) was
sec.
• This is surpris ing: the major cause of incidents on most Western World pipelines is lhird party interference. and
sec is a relatively minor prOOlem . • In 1986 we only knew about one type of sec - tvgh pH! 49
SCC: Failures in Canada 1954 - 1984
1985 - 2003
•
""
__2001_ . 50
25
scc: Low pH
('near neutral') Failure
.From 1977 - 96 there were 22 SCC failures in Canada .15 on gas lines _6 circumferential cracks, _9 longitudinal cracks
.7 on liquid lines .1 2 ruptures and 10 leaks 'see failure of gas line - USA - 2003 'Typically, low pH sec is eeeccieteo we very shallow metsucss. It is toone! whe re the re is a loca l absence o f C P, 'Ari th a coating missing (in wet anaerobic soil ). or disbonded
'More low pH sec fa ilures on gas lines are reportedin Canada.But. there are 4x as man y tape-coated gas lines as liquid lines in
Canada. Hence. liquid lines are 2x likely to crack than gas lines, on a mile per mile basis.
0_2006-.
51
SCC: Factors for Low pH ('near neutral')
• The SCC causing these failures is called 'low pH SCC' • It has an increased tendency to occur at higher stress levels .
• However, these sec failure s have not been confined to high stressed lines • sec has caused fa ilures in lines at stresses down to 53% SMYS.
sec
-l ow pH gives transgranular (sometimes called 'quasi transgranutar) crack s . -These cracks are similar to corrosion fatigue cracks. -corrcso n fatig ue cracks are fatigu e cracks accelerated by the corrosive environment. 52
26
scc: Factors for Low pH •
('near neutral')
sec
Most (94%, of these Canadian failures were associated wit h 'stress raisers'; mechanical dam age (gouge , dent ), significant me tal loss due to corrosion, or a weld. •
Addi tionally, the failures were primarily on disba nded coatings and on field applied PE tape coaled lines installed between
1968 & 1973 • Tape coatings have high CP resistance which prevents otsbo noe o areas from be ing cat hodically prote cte d. • No reported failures on fus ion bonded epoxy pipelines
•
This cracking has also occurred in USA. Brazil. Italy, Russia, etc..
cl_2OOlI_'
.....
"Fl(!l(I.-applied tape coaling
e-"'
o-
---.- , ~ ~ " . -
.......
-._.,...-_
__
53
..., - ~ -
scc - Factors for Low pH
('near neutral')
see
at.ow pH has a dilute carbo nic acid environment (5.5 to 7.5 pH)
see
_ Low pH can be either axial or transverse to the pipe axis _ A wide range of pipe sizes, grades and manufacturing processe s were involved, which suggests specific pipe steels or pipe mills cannot be identified as con tributing to _ The incidents have occ urred at locations remote from compressor stations" sugge sting temperature is not a factor.
see.
I
""
r All steels
rJI
see
"l ow pH
sec is ....,.. ............ the _ arge 01 a COtfV'l'$SCII' st._ '"
_ _ lI>8 _
arg.. """ """'''''' of ~ staOOos Io< liquid Ionn
27
see - Environment* for Low pH ('near neutral') _ Near neutral SCC was not documented until the late 1970s and was first identified on buried pipelines in Canada where tape-wrapped pipe contained wrinkles in the coating that trapped water with a pH between 5.5 and 7.5. _ The cracking environment appears to be a diluted groundwater containing dissolved CO2 , The source of the CO2 is typicall y the decay of organic matter and geochemical reactions in tile soil. _ This form of cracking occurs under conditions where there is little, if any, CP current reaching the pipe surfa ce, either because of the presence of a shielding coating, a highly resistive soil, or inadequate CPO _ Typically, the SCC colonies initiate at 00 surface locations where there is already pitting or general corrosion, The mos t obvious differences between the two forms are the temperature sensitivity of high-pH sec, the fracture morphology, and the pH of the pipe environment.
see occurs at a free corrosion potential of · 760 to . 7g0 m V ccs _e-.e.-",_." __s----......_ _...__
"Near neutral
F " ' ~ _ " " " 'F " _ " ' _
.""'"-'9_
~
c.-.., . _ ASIoIE Fe 2ta
~
55
2
scc: Time for Near Neutral Axial SCC to Fail
Hoop stress
16 ncidents
~ 25
"g; ~
20
~ 15
1---- - - - - - -- - - - - t - - -- - - ----,::::-- - - -
1----- - - -
10 1-- - - - - 5
o c-s
."
te-a
21·25
Service life to First sec , years
"
28
see: Time for Near Neutral Transverse see to Fail _ The initial average transverse SCC pipe age is 3.8 years less than the initial average axial SCC age. _ This difference may indicate that the stress level in the transverse crack case is higher than the axial crack case causing the cracks to grow faster or more continuously.
A"9 Age " 17.6 years SO " 4.8 years
70
•
Transverse cracks
'''''''''
so so
~
~
•e "30 c
•
c,
20
70 0
f----I11_15
0_ 2006 _ ,
Transverse crad<
from CEPA sec RecornrrencIO
Service Lif e to First
see - Low pH
sec. years
"
(Near Neutral)
_ Coating has a major role in low pH SCC.
_ PE tape coating and shrink sleeves have been involved in over 80% of the Canadian failures.
see
LaboratOl)' tests show polyethylene tape coaling shields CP current whereas FBE and coal tar coa tings do not'
0_2006 _ 61'
---"'.. ',-. _
_
... _
__ __
.__,,.. ... ' _. 0.--.""""-
' _.-..-., ....... _
~ ._
~
. • 0'
_
.... , ... ,
_ ~
se
~- ",..-
29
see· Low pH (near neutral) -
Key factors (NEB)
_ The National Ene rgy Board of Canada
see
concluded that
_sec in itiate s as a resu lt of the complex interaction of three con diti on s: _ 1. a potent envi ronment at the pipe surface _ A num ber of soil and groundwater propert ies then playa role in producing a pole nt environme nt at the pipe surface.
_ 2. a sus ceptibl e pipe material, and
_ 3. a tensi le stress ". _ All three cond itions must be present
to- sec to occur. O ~d
"" .......,. _ _ ""
_
_
_ "' ,
_d_"' __...._._
_o:ar;o"-b_"_ • ....
F\w;>'' - ' ' ' ' •
see · Low pH (near neutral) -
- - . y .... _ " " ' _ _ ... _
59
Key factors (NEB)
_ T he National Energy Board of Canada concl uded th at:
sec
to attack a pipe surface . _ For th ere mu st be a breakdown in the pipe coating and th e CPo
sec at It1e base of a pil
30
see - Low pH
(near neutral) - Key factors (NEB)
_The National Energy Board of Canada concluded that:
_sec
in Canadian pipe lines is primarily in pipelines built in the 19605 & 19705, using po lyethylene tape as the coating .
sec
_ 73% of occurrences were on polyethylene tap e w rapped lines. aThis coati ng has tended to sepa rate (disband) from the pipeline and allow moisture to contact the pipeline.
a a ecause polye thylene lape is an insulator, it shields the pipe steel from cathodic protection cu rrent, even if it disbands. 61
see· Low pH (near neutral) -
Note on tape
coatings· a r ape coating s, such as the polyethyl ene-back ed tapes used predominantly in the early 19605 to 19805, are spirally wrapped around the pipe with an overlap at the helix line. • 'Tentinq " occurs between the pipe surface and the tape along the ridge created by longitudinal, spiral, and girth welds _ Tenting also occurs at the overlap between the helix of the Map.
_ When the tape disbands from the pipe, moisture can accumulate beneath the tape surface, particularly at 'wrinkl es' and 'tenting' in the coatin g. _ The tape itself has high electrical insulation properties, thus prevent ing cathodic current from reach ing entrapped moisture beneath the tape at the pipe surface .
_ In Cana da, about three-quarters of reported near neutral-pH SCCrelated service incidents have occurred under these tape coat ings. _ The cracks tend to occur at or near the toe ot the seam weld where stre ss is concentrated and water has acc ess, as well as where the coaling has been damaged or disbanded 62
31
see - Low pH
(near neutral) - Note on coal ta r/asphalt coatings · _ A sphalt and coal tar co atings are relatively thick and can be brittle . _ The coatings can disband . especially due 10poor surface prepa ration .
_ Over l ime , the volatiles can disperse. leaving Ihe coating relatively brittle.
_ Unlike tape coatings, when these coatings disbond , they usually, but not always , become saturated with mo isture and conduct cathodic curren t, thus prote cting the pipe . e s o, when these coatings are 'aged' are permeable _ If the coa ting is brittle, it m ay break into pieces. also allowi ng a path fo r the cathodic current protection .
_sec m ight still occur when tile soil is so resistive that the cat hod ic current cann ot reach the pipe. _ For the se coating types, there is no preferential loca tion, but SCC m ight occ ur wherever disbonoment or holidays occur
_'~
see - Low pH
e--.,
~
:--, "'
_
"-
__
",-,, _
~,
... . ,., _ _
63
(near neutral) - Note on other
coatings · . 11 is genera lly agreed that fu sion-bonded epo xy (F BE) coatings , which are often the coa ting of choice for new ly installed pip elin es in the United St ates , are an effective protection agai nst SCC. • This type of coa ting (FBE) is a perm eable coating that allows C P to reach the steel" . " Extru ded polyethylenes and three layer composites also appear to be effectiv e", except possibly at tape-wrapped girth we lds . • The se types of coating are im permea ble, shielding coatings that remain tightl y bonded to the line
sec
Resea rd! indicates IhaI gnt-blasted surfaces are geoeraIy mote resistant 10 high-pH inibalion than miI-scaled surfaces. primariy beca use gnl bIa'sbng imparts a oompressive residual stress., !he pipe surface . The rnajon!)' of ~ FBE coatings are applied in coabng mills over gril-blasled surfaces. The older bilurNnoo.r$ coatings WOlfe freQt>efl1ly applied Oller ee dl!dl on ~sealed surf3Oe$. More recen~y. bituminous coatings have eeee applied ., the m.lI using a 0JfllrI'lerCia1blast cleaning
_e..-
""""""
",
~ " , _
-- "- - ~ ""' -
,
_ _ •_ _ «. _"-, ...
~"-_",
,,
,
,
.•
~
,--,
_
32
SCC - Management
65
CONTROL OF Low pH SCC: Selection of Susceptible Segments *
•
•
Pipeline segments that have/are"': 1. Operating stress >60% SMYS 2. Age 0!: 10 years 3. All coating system s other than FBE If ALL of these are presen t then the pipe should be assessed for • In addition prior indica tionslhistory of (service, hydratest failures, etc) should be evaluated unless conditions that led to them have been correct ed.
sec.
sec
"s..OOT WoOtI sec. ~ 2003
1_ lhe ~lll)tlllyJolY> A ee--t.
------
CNotman d w..cE TG 273 0tI sec OAt 001 "'_""SCC _ _ Z003
40..... a private discI.oMoon """ Or R F _: this is tile same criteria (."""'1'1--......, _ is ~inAS ME
831 8S1or~'lI~pH
sec
0_200II_0111
33
CONTROL OF Low pH SCC - Note ' on CP
sec
•
Near neutral-pH is most preva lent on pipelines with shielding coatings (e ·9 - tape) and has occurred where the pipeline is appare ntly pro tected based on CP in formation .
•
Neverth eless , it is worthwhile 10 maintain adequate protection to avoid sec an d corrosion al or near holida ys ,
•
Effective CP also wi ll minimize the occurrence of near neu tral -pH non-shielding coating s.
..
_e--~_
_ _ _ ...."...... _
sec with
0.. _ . . . , . . .. _ _ .-._ _
e-.o .. _ _
SCC GROWTH RATES ' •
High pH and near neutral-p H s ec have grow1h rates in the range 2 x 10-91 0 2 x 10-8 mm/s (0 .06 to O.6mm/yea r)
•
These data are from field excavati ons
C_2OOli_'
ee
34
ALL
see - Mitigation
& Management
sec.
. If you suspect you have you can mitigate: . Improve CP, Temp and Pressure Cycling . • This slows down the growth.
• Repair and Recoat e scme repair methods such as welded sleeves are considered acceptab le , but others (e.g. Clockspring) are not yel consid ered proven for cracks.
_ Retest and Recoa t _ A hydrates! (e.g. a 'sp ike' test } will fail large de fects _ Test (2-6 years) to 11 0% SMYS to remove near critical
Tape wrapping
""",,-..,.....,"""""""-"'..
defects _ Retest raises 'proportionallimil' which helps reduce future local ised micropfastici ty on the pipe surface
a s erecnve replacem ent _ E.g. near populated areas. to reduce overall risk _ Replace or Loop Affected Areas _ Smart Pigs & Selective Replacement e son e pigs can detect cracks
C_21X16 _'
ALL
see
- ..
....
_
...-) 69
& HYDROTESTING
. ASME 83 1.8S-2001 require that all indications of see are addressed immediate ly (within 5 days of reporting)
~-,1S\l 1
. ASME 8 31 .8S requires hydrotesting to mitigate see threat. _ The literature suggests a hydratest to 100%SMYS OR 1.5 X Design OR a Calcula ted level _ 24 hours or when you are confident of max pressu re
KJ 1.1l. 'i ! OO I Srp PLEME..'H TO IU UI
"'
\l .-I.·H C I~ G
S, ·SI 1:\1 I',TIG RlT Y
",
(; .-1. S ""·f_l _" f .~
._--------
- Do not cycle pressure
35
SETTING HYDROTEST INTERVALS FOR SCC: Illustration
1. 0.t.O ['TiC " )'
" r - - - - - - - - - ,-- - - - 2c - - - -,------, • .
d~I~1
::::::::::::=---------
~ d--lt '" 0.4 0.5
0.6
07 0.8 0.' 0.95
, "_
•
2c1(Rt)"'O.5
2OIl6 _ ' In _
,
• ....,..,!low SltftIgIt>,;;
~
1 , 5ougIl1M..- oh,IIW""IfI _
•
""" may be _
~
A.., " 2c.t
...... ff!(lla(Je(I_Ai....
71
SETTING HYDROTEST INTERVALS FOR SCC: Illustration
.." .. ~ •
u
u "
~
..
/
., .... u
-a- .
see
-e
•
r--
-
a ,
Failure of at operation
"
-
J
I , --
I
"
DESIG N PRESS URE (72 pe1"CeI'II SMVS/
~
E
E.
'ii
.."
.." .. 0_
Growth
/
HYOROTES T PRE SSURE (100
see
~
SMYSI
Failure of on hydrotest
"
..
"
..
"
2e1(Rt )AO.S (normalise d defect length)
..
"
20'& _'
.. 72
In l'"s eumple. _
....ength = I . 1!m, .. ,hDuQ/I ...... "",an of """""I..
atl(l
yield may be be"...
36
OTHER CRACK·LIKE DEFECTS IN PIPELINES
IC> Po""""" 2006 R....6Jl
'RAILROAD' CRACKS .Pipe is often transported long distances by rail, road or ship _In the 19605 a number of leaks and breaks originated from cracks in the pipe wall, caused by fatigue loading during transportation by rail. _The fatigue cracks were caused by repeat stressing - the static stress is caused in the lower levels of pipe by the weight of the pipes above, and the repeat loadings were produced by vertical accelerations ,
_Hence we must adopt good loading practices if our pipe is to be
transported. _API published guidelines (AP I RP 5L1) as far back as the 1960s*
37
INCLUSIONS _ Inclusions in the pipe body are not considered significant if they have passed a pre-serv ice hydrotest _ However, they may be a site for hydrogen cracking in sour service pipe line s
/
Inclusions
H'
HARD SPOTS _Hard spots (dollar spots) are local hard zones caused by excessive local quenching during roll ing. _ T hey are typically <10" diameter, and may ca use local out of roundness _ this is because the ir high streng ths prevent them from yielding in the expander and duri ng the 'U'i ng and 'O'jng in the pipe mill.
_ They can have tensile strength s of 130 ,000 to 200,00 0 psi in the centre port ion _ The high hardness can lead to cracking if exposed to a hydrogen charged envi ronment. _ Generally, Ihey are not a problem , but they do increase susceptibility 10 other types of defects/cracking .
Hard spot \
() 6 ) re
38
r HARD SPOTS (cont.)
_ The most common cause of failures associated with hard spots has been hydrogen stress cracking. _ For hydrogen stress crackin g to occur, three co nditions mus t be
met
_a ste el of high hardness and high strength
(the hard spot)
. sufficient sustained tensile stresses (hoop stress ), and
_a source of at om ic hyd roge n (probably from the C P reaction) Hard spot
Coating Poor
Hydrogen cracking
\
W
C]"
HARD SPOTS - Case Study·
o
. PIPELINE - Canada, 762mm, X52 , gas pipeline. buill 1957 . • Hyd rotesl ed in 1957 to 8 .1 MPa. Pipe coal ing
= as phal t enamel.
. Ruptured in 2000, at pressure of 5.6 MPa .
_ INSPECTION - Line inspected for metal loss in 1981, 1991 and 1998 using
a MFL pig. _ Near the rupture locat ion, the inspectio ns had revealed two den ts and so me minor corrosion
. PROTECTION - During the last 10 years so me pipe-to-soil potenti al surveys indicated that the CP current rea ching the ruptured sectio n of pipe was lower than the industry standa rd .
a r t iese locations checked using pig data - where req uired . suitable remedial actio n (e.q. increasing the rectifier output ) was taken . • PR EV IOUS FAILURE S? - In 1996, a leak occurred on the mainline. _ A metallurgical report indicated tnat the leak had initiated in a hard spot created during the origi nal pipe man ufacture. 0_2006_1 ~_.-..-.-
.. <:..- _ - . . . . - .......... _
..... '"
78
39
HARD SPOTS - CASE STUDY (cont)'
()
_ FA ILURE IN 2000 • No coating remained on the section of pipe whe re the fra cture originated. _ The coaling on the pipe secti ons both up stream and downstream of the rupture locat ion appear ed to be intact and adherenl lo the pipe . _ Shallow surface pitting corrosion (undetectable by the in-line inspections) had occurred at the fou r o'clock position coincident with a localized area of higher hardness, or hard spot . on the exterior surface of the pipe. _ Cracking had initial ed in the hard spot.
_ T he most co mmo n cause of failure s asso ciated with hard spots has been 'hydrogen stress crac king'. _The sha llow external corrosion which occurred in the hard spot wou ld have increa sed the stress in the pipe al thal localion and probab ly facilitated the initiati on 01surface cracks.
LAMINATIONS _....,*"'"E_.~ J "
f1_A R . _ . " f
""
"""""',G " .'.-OIP'P"_
""-"R_ "' _ ............ _ "''-_.","_0 ...""'......,'""",'
....
60
40
LAMINATIONS atamlnattons are manufacturing defects: _They have survived the mill hydrates! & the precommlsslontnq hydrotest.
J90:100%;M~S Jam PIPE MILL TEST
FIELD HYDROTEST
_The hydrates! is a proof load for internal pressure. Therefore, the fact that a lamination has survived the hydrates! may not be relevant if the pipeline is subject to bending or other forms of loading. atamlnanons that are not in a hydrogen-charging environment, and are parallel to the surface of the plate are not structurally significant.
LAMINATIONS (cant)
a t.amlnauons inclined to the plate, or multiple laminations through the wall thickness may cause a leak path _There have been failures due to laminations when they have been orientated at an angle to the pipe wall: they reduce the effective wall thickness and have caused failures. _Usua lly the failures occur during the pre-service test.
_Beware welding onto laminations (the lamination can open up and cause a leak path. _Beware of laminations associated/ad jacent to weld or other structural discontinuities - they may lead to failure.
82
41
BLISTERS a t armnauons in line pipe carrying so ur product can be a problem :HIC, blisters
_ Guidance for hydrogen charged bli ster s and lami nations are given in API 579 _ API 579 gives acceptance limits, and conditions to be met for acceptance
,,_ _, ......
83
ADDITIONAL INFORMATION
0_1006_'
84
42
GROWTH OF ENVIRONMENTAL CRACKS •
•
An y crack Initiation of environmental cracking , such as sulphide stress cracking of carbon steels , is usually c onsidered unacceptable due to the rapid rat e of subsequent propagation (growth). However, we do have some fund amental understanding of th eir growth under static loading : Environm ental crack s grow due to the environment, but they can reach a size when they can start to grow by a fracture mechan ism . •
The stress intensity (1<;) of the crack at this size da/dt exceeds a critical stress intensity lor crack growth,
•
If the Ki value of a crack exceeds Kiscc the crack will INITIATE AND GROW at a rate dictated by the material. environment, etc .. Hence, if 1<;<1<;"",_the crack will not grow . II I<,>K,,,,,, the crack will grow, The RATE OF G RO WTH (daldt) will dictate how long the crac k takes to fail the structure,
Fail
K,~
•
• •
Grow
The structure FAILS when K;=K..: (the fracture toughn ess ) (assuming that K;.,>K;scc)' You can measure K.scc. K.c and daldt in the lab. See API 579 and BS 7910
K
C_2006_ •
85
HIGH/LOW pH STRESS CORROSION CRACKING • OBSERVATIONS OF ONE EXPERT II sec ('< ,
h "w
1,0"
1.0<.'10.
M
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"
n_.
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r
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to ""'" '"'"
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,.
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86
43
MANAGEMENT OF ALL
see
Deterministic:
,
--
_.
Probabilistie (given that sec conditions ('liabil ity) arc present):
_.
---- -~ ro_ ~
I~
J""Ero SMAU.
-=~
--
-
.~~
~'O
~ '0_
----
._,~ ~
~ ro_ro
44
How to Assess Weld Defects
Penspen Integrity
.
__.
......, 1
INTRODUCTION - Hydrotest Stresses in Welds _ Girth welds
". manufa ctured in the field. and the stresses created by the hydrate sl will be <50 % of thai expe rienced by the long itudinal seam welds
2
INTRODUCTION - Line Pipe . Pipelines are made up of sections of line pipe welded together. _ The line pipe is delive red in lengths of about 12m to site from a pipe mill. _ The line pipe sect ion is manu factured to a standard (e.g . API 5L) , and is a low carbon steel. It can be : . 'Seamless' (i.e. it has no we ld) - seaml ess pipe is ('l usually smaller diamete r « 24"), or ~~
. 'Welded' · made from steel plate which is formed into a circle (like cigar ette paper) or wrapped in a spiral shape, and we lded at the pipe mill . There are various types of weld used. but the y can be sum marised as either:
~ ~ "i 00
~ '\;
_ Longitudinal
. Spiral 3
INTRODUCTION: Longitudinal/Spiral Welds i n Line Pipe
_L ine pipe welds are made under factory conditions, are inspected, and also tested at the mill. _ T hey are unlikely to conta in large defects or be a failure problem when they arrive at site. _ Also , after being welded into the pipeline, the line pipe (and its longitud inal weld ) is subjected to a pre -service hydrotest that would 'find' larger defects or poo r quality welding.
•
2
INTRODUCTION: Longitudinal/Spiral Welds in Line Pipe
The he al a ffected zone (HAl) is that pari of the parent metal where lhe meta llurgical properties ha ve been changed by the heat of weld ing
HAZ
parent plate
ca~··· ·_······'
toe
seam weld doub le submerged arc we ld (DSAW)
0_200II_·,
5
INTRODUCTION - Field Welds (Girth Welds) in Line Pipe _ The line pipe is welded together 'on site' or 'in the field'. These circumfe rential (girth) welds will not be as good a quality as the factory welds . 'Fillers'
Capping Pass
-----l--~ Each oItllese pas _ may be ..., by ddletenl wel dIng IN.... Iong.
Hot Pass (or secood run)
Root Pa ss (or 'stringel"' bead )
pipelIne wrNd
0_200& _ _
6
3
INTRODUCTION - Field Welds (Girth Welds) in Line Pipe
'Y
girth weld shi eld ed metal arc w eld (SMAW) HAZ
too
pa ren t psate
...•...... root
The heat affec ted zone (HAZ) is that part o f the pare nt metal whe re the metallurgical properties have been chan ged by the heat of welding C_:lOO5R
7
INTRODUCTION - Undermatching and Over matching in Welds
yield~ strength of weld g reate r ~:;-----------;;;; ~ th an thaI of parent plate ,
OVERMATCHED
aod lensile strength of weld greater than thai of parent pla te
yield strength 01 weld le ss t h an thai of par ent plate .
UND ER M ATCHED
aoo tensile strength of we/a less th an that of parent plate
yield strength of weld eq ual t o that of parent plate.
parent plate
HAZ
MATCHED
aoo tensile strength of weld equa l to that of paren t plate
weld
8
4
INTRODUCTION - Stress Concentrations in Welds
-------f----T------~ misalignment due to wall thickness mismatch
misalignment or axial misalignment due to out-of-roundness or diameter mismatch
9
LINE PIPE LONGITUDINAL SEAM WELDS weld
5
PIPELINE LONGITUDINAL SEAM WELDS· Defects _The main problem with defects rema ining in a longitudinal weld is that they may be a source of fatigue cracking _ If a pipeline has its interna l pressure cycled. it will cause cyclic hoop stresses in the pipewall . - These can cause defects in the weld to grow in size _ The defect may grow to a size that can cause failure
_ Modern line pipe is free from these large defe cts. ~_
•.
_~ .
_,..", ... ",_ _ .
,_,
._ _
er-_..,-.-
ELECTRIC RESISTANCE WELDED (ERW) LINE PIPE
7
ELECTRIC RESISTANCE WELDED (ERW) LINE PIPE ' _E RW line pipe is made" by cold forming previously hot-rolled plates or strips into round "cans" and joining the longitud inal edges of the cans by a combina tion of localized electrical resistance heating and mechanical pressure. _T he heat-softened edges were forced together extrud ing excess material to the outside and inside of the newly formed pipe. _ The excess material was immediately trimme d away leaving smooth surfaces or at most a
_--_ - _
small protrusion along the bondline. ____ .. ..---"'.., _..'"w_... _ _ ,,_..... __ .... ---. --,.. . . ----,'*',.._""""'-.....-, ...."""'_ . ....... . --"""""' ..... "" _----~
ERW LINE PIPE: Weld .The process resulted in a narrow bond line and an associated local heat-affected zone.
,< Heal Affected
.,
Zone
, We ld
"
\.
line
Pipe
te
8
ERW LINE PIPE: Quality a ln many instances in the past. and in all cases with modem ERW materials, the bondline/heat-affected-zone region was also subjected to a 'po st-weld heat treatment' _ The purpose of this was 10 eliminate zones of excessive ha rdness from the initial welding process
a'rhese zones could be susceptible to various fo rms of environm ental cracking.
Heat Affected Zone
Weld
Line Pipe
a ERW line pipe thai is not heat treated adequ ately may crac k
. Prior 10 1960, many sizes and grades of ERW pipe were tested by the manufacturer to levels of only about 75 percent of SMYS, so large defects could survive _ ERW line pipe must be treated on a case by case basis
0_:1006_
_ -_ . _ _------__ -'--"--_---_
_ So me 'old' ERW line pipe has poo r welding , other has good we lding ,
..._._-,,---' . ... . ---...... ...
,
...
...
OLDER ERW LINE PIPE': Defects e oicer (up to the 1960s) ERW line pipe manufactured using low frequency' (60-360 Hz or less) AC, or DC, or e any ERW line pipe made using 'dirty' (high percentages of non-metaltlc inclusions) steels may contain defects such as: . 'Cold Welds' (caused by a lack of fusion between the parent plates due to inadequate heating and/or pressu re during the welding process . 'Stitching' (non-uniform heating results patches on the surface where no bond exists) . • Plate Misalignment , . Heat Treatment Misalignment (the bond line can become twisted as it moves through the rolls ) HookCrack . 'Hook cracks ' (metal separation around ~ ..... .... non-metallic inclusions in the plate. Inclusions follow the weld flow and cause cracks) (".E RW line pipe made using ee more modem Ibgh frequency (- 400,000 Hz)
-,..- ...... _.
DC, or high freque ncy inductance (HFI) methods should not have mosI of tnese proble ms) ,- - --~ - --- - """~
.... _,-
18
9
OLDER ERW LINE PIPE: ' Co l d Welds' .Dirt, grease, scale, or other oxide films on the skelp could and often did cause enough interference to prevent adequa te heating at the bondl ine interface. • Momentary reductions or loss of current cou ld and often did result in isolated or repeated area s of nonbonding called "cold welds". _ Cold welds could be partly through the wall thickness or all of the way through . _ Even if a through-wall cold weld was formed. it might not result in a leak. beca use typically such areas were com plete ly filled with a scale that formed from the surfaces being exposed to oxygen while at a high tempe rature. _ A significant number of cold welds in close proximity could sufficie ntly reduce the strength of the bondli ne that a rupture would occ ur whe n the pipe was subjected to pressurization.
_
.-,-_ . .-. . _._.4_ .. __._-,.--_ ...._--------.. _-
ts
OLDER ERW LINE PIPE: Corrosion and Fatigue e'rhess ERW welds can have problems in service : .Preferential corrosion" along the ERW line a particurarty found in high sulphur materials that have not been heat treated , as they are more suscep tible to corrosion due to the microstruct ure and the presenc e of non-metalli c inclusions. _ The weld area corr odes at a higher rate than the surrounding material. _ The result is the formation of a v-sneoec groove along the weld line). _ Do not assess using RSTRENG, etc.
_Fatigue (if the pipe line is subje cted to a cyclic loading regime) _ Summary- All pre-1970 ERW pipe and lap welded pipe is cons idered susceptible to long itudina l seam failures
"- - _----_.... _--_ - _ _ ... _
....
.. _
.... _
..
00,._
20
10
OLDER ERW LINE PIPE: Hook Cracks and Fatigue
/'"- -
Weld
....••. ~ _ ..
Hook crack Fatigue crack Inle rnal pressure
hoop
stress " _G ' _ ~ "'
__"
.._ _
..,...,._
~
"
ERW LINE PIPE: New (High Frequency) _ From 1962, manufact urers began to convert ERW mills from low-frequency welding equipment to high- freque ncy equipment (450,000 cycles) .
High Frequency
a After 1978. it is believed that few if any lowfrequency welders were still being used.
_With the use of high-frequency current, the problem of contact resistance is virtually non-existent. _ As a result, high-frequency-welded pipe tends to be relatively free of the bond line defects that we re common in the low-frequency and d.c.welded ma terial.
C_2OOIIl_'
No bondl ine defects
_--,-_ __
. .... _- - - ... ---_ .. ... -.. -,-----_.. ""'"--"'---'-_
...__ • _ _ J"'
~ -- ,
'
•
•
,.
_
22
11
ERW LINE PIPE: New (Cleaner Plate)
_ The use of cleane r plate materials (low sulphur) has eliminated problems such as hook cracks , and grooving corrosion _H ydrotest failures per mile decreased from levels as high as 6.5 per mile in the 1940s, to a level of 0.01 per mile in 1970 for pipelines tested to levels of 90 percent of SMYS or more.
Clean Plate
No grooving corrosion & hook cracks
__-_ _---_ __
.. -_. __ ........ _------------.._._----_ ... ... -... .._------_ _ _ _ 00
'_-
23
ERW LINE PIPE: Summary Low Frequency Method
High Frequency Method Bondline Problems
_ Solution
Hook cracks & _ grooving corrOSIon Solution Poor quality plate
I
Clean plate
"
12
ERW LINE PIPE: Managing Integrity of Old ERW lines* . Do I need an Assessment Plan? Does my ERW pipeline need special assessment? ERW Line Pipe can be categorised: •
•
•
1. Clear evidence shows that time-dependent dete rio ration of seam anomalies is occurring • Pipeli nes in this category will req uire a special seam-integ rity assessment plan . 2. No direct evidence of ERW seam deterioration , but cond itions of ope ration and attributes of the line indicate seam deterioration is likely. • These pipe lines will req uire a study of the attributes , the op erations, and the resu lts of other integrity assessments 10 determine if a special seam -integrity assessment plan is necessary. 3 . Clear evidence that no time-dependent seam deterioration is occurring. • No special seam-lnteqrtty assessment plan is needed for segments in this category
-••• _
.
, . . ..
... " " ' _
"' _ M ~ ...- _
'__'...h''' ....",._ .
"'"
....
--
_ . ' , 00 . . . . . . _
. .,
",
- -~ ~",
25
.
ERW CASE STUDY'
:~;;d~~5~i~~~ne
U~
- Built in 1966, India. "' _ER W. _ _I
,..,.
i, l~~~~~~!j
_H ydrotested to 114 kg/cm2 in 1966. _H ydrotested to 76 kg/cm2 in 1983.
\C
~~~!~~!!~g
~
_F ailed in 1997 at 47 kg/cm2 _Fa iled along ERW weld. eccrrostcn on both external internal ERW surfaces
C
_'POI'
2006 Ro, 6I1
··,..... _
".Croo.""''' 'Y . . .
an d~
, ""'
....
26 ~ '''' "'' ''''C TOO"_· .
eo.. """Y
s",• .".",."....,.•.
Konnon C,'-'rwno " ....,_.,..............
13
ERW CASE STUDY· _ Defects seen on frac tu re surface - lack of fusion due to im prope r edge preparation during the welding of th e pipe which have subsequently grown due to general internal corrosion . _Cleavage fracture on the fracture su rface indi cating low toughness weld . • During the long service life of the pipe , both the lack of fusion area have undergone subcri tical growth due to corrosion I erosion on the inner surface w hich is possible in view of the 6' 0 clock pos ition of the ERW sea m Note small opening at fracture
0 _"""" lOO6Rov6l1 ' h"' A~ , "' .
em.. 000",,>,'1M"' ,,"
" ~ "Il UO[>" " " ,'.... A .,... >Iu<>f _ . """"""""'" ""...... C,..."..-., • .
"''''"1' ....... ""...
27
ERW CASE STUDY· _xeD, 10" diameter, 0.5" wall thickness oil flowline • ERW fine pipe
_Failed from hook cracks
.Pressure increased to we ll shut-in pressure due to . . . • sudde n shut down of gas and oil separation plant
za
14
PIPELINE GIRTH WELDS
X65 with stainleu steel cladd ing
C_2OOi_
29
INTRODUCTION: Defects in Girth Welds
•
30
15
INTRODUCTION: Girth Welds ••• History _ The use of steel pipes and the introduction of electric arc welding in the 19205 established the techniques for modern pipelaying and today we have soph isticated automatic wel ding bot h on and offshore. a A dvances in pump technology even tuall y made it possible to move oil cheaply and qu ickly at pres sure s of up to 2,000 psi and beyond. _ W ith the advent of high tensile stee ls it is now possibl e to weld XeD pipe and soon we will be welding
Xl00
at
INTRODUCTION: Girth Welds ••• Standa rds . Pipel ine girth welds are welded using a standard that cont rols the procedure and materials.
_The most common girth welding standard is 'API 1104'
-_,-.... _-
•
....
a This API standard was based on the standard 'Unfired Pressur e Vessel Code' , which was adopted by ASM E in 1931. a AP I first adopted radiog raphy to inspect girth welds in 1953.
32
16
INTROOUCTION: Girth Welds ••• Welding
DLJ
_ The we ld ing crew begins the process of joining the steel pipe into one con tinuous pipeline using manual, se miautomatic or automatic welding proce dures .
_ Welds are then x-rayed using x-ray mach ines 10 as sure pipe joints have been welded together properly. _ After the welds are x -rayed and i ns pecte d , the pipe is cleaned and co ated to prevent corrosion. . Mosl line pipe is coated at the coali ng plant with a hard baked-on epo xy or extruded polyet hylene coal ing 10 preven t corrosion of the steel. It is only the weld s thai are coated during construction.
..... ,J!!lI..... .JJJ:~1::& l ~
---.---SlI' ..... ....
. .,.
_ ~
pl-''''' - ~' '''
1;_20015 _
~ _ - " .r .O
--
__....
_
33
INTROOUCTION: Girth Welds••• Types of Pipeline Welding ... 'SMAW' _ We use two methods for welding line pipe in the field _ 1. Manual arc welding - the most common process e also know n as SMA (shielded metal are, or stic k) W elding a erecncde rod is ceramic-covered metal
md
a e'ectrooe rod me lts and is added to weld me tal (it is called consumable) _ the electrode cov ering melts (cov ering the weld pool with liquid flux) , and also gives off gases which help wit h the shie lding _ aMer welding is finished , the we lder chips off th e solidified flux (slag ).
• 2. Gas metal arc (GMA) W elding...
17
INTRODUCTION: Girth Welds ••• Types of Pipeline Welding ••• 'GMAW'
. We use two methods for welding line pipe in the field: _ 1. Manual arc welding - the most common process _ 2. Gas metal arc (GMA) Welding e arsc ca lled 'MIG', or 'metal inert gas' we ld ing . rol1 of wire used as cons umable electrode _ flow of inert gas (argon, helium ) through weld ing torc h towards workpieces, 10shield weld from atmosphere _ may be manual or automatic
0_
2OD$ _
35
INTRODUCTION: Girth Welds ••• Types of Pipeline Welding
•
G~AW
-
·~tcchani=1·
SMAW - Manual
_ Gif1h """9ldong is a produc:bon line oonstrudion W11h tile worI
0_20D5_'
36
18
GIRTH WELDS: Assessing Defects • Somet imes we need to assess defects in pipeline girth we lds: • On new constructions - e.g. using a new weldingJinspection methods and creating or finding new or mor e defects. • On finding a defective girth weld(s) during an in-service inspection. • A failure due to a defective girt h we ld occurs (failure investigation )
37
GIRTH WELDS: Fa ilu r e s ? • Ge nerally, pipe line girth we lds are not a prob lem in pipelines: • they are not a major cause of fa ilures • only 2% of all fai lures in USA gas lines are due to girth welds . • the majority give leaks not ruptures, and the re has been no recorded casualty/fata lity ca use d by them in the USA.
38
19
GIRTH WELDS: Axial Stress • When we have defects in pipeline girth welds we are interested in AXIAL stress • Internal pressure gives an axial stress • Extemal loads such as ground movement, or installation , gives axia l stress
inte rna l pressure
Axial loads
7
~~"di"9 loads
39
GIRTH WELDS: Defects ," "" cap
»>
Lack of cap fusion
porasi! crack _ l ack of root fusion
0
l -(/ ~
root
J.. .
• l ack of sidewall fusion
Lack of inter-run fusion slag
--,"'"'
---_
....
R
Dooo,o. ~ "'
_ _ ..
20
GIRTH WELDS: Defects in 'Old' Welds
<_ _ .. _
C."'"",",,",, _
,,0000<_. _
" , - .... ...
d_
E......-..L_ .·'"
GIRTH WELDS: I nspe c t ion using X Rays . We inspect new girth welds by: . X ray (most popular)
r
a ultrasoruce
__
.. ~
'I' 'i . ,• ~-raY J
of broken arm
----"
2\
GIRTH WELDS: Inspection by X.rays . Radiography (gamma or X-rays ) is most commonly used to check the quality of weld s.
I x"" ' ).
""0 ') film Planar deled
JNon-planar deleel
\ Incom plete penetrat ion from 5 to 35cm
GIRTH WELDS: Inspection by X-rays _ A film (negative) is placed on or behind the weld and the radioactive source is placed on the opposite side (with the weld between the film and the radioactive source) and allowed to expose the film . _ This exposed film is developed .
_ A film interpreter chec ks this developed film to determine if the quality of the weld is in accordance with the predetermined assessment standard.
• -. .. v
~_2C06_1
___
\\
\
I I 44
'_
" " '- « I
" ' Y " '~ ~ ~. . . . c . ~
_
22
GIRTH WELDS: Inspection by X -rays . Radiog raphic inspection of girth welds , introduced in 1948 , soon became the universal tool for ins pecti ng a portion of all field girth welds. and became mandatory under API Standard 5L in 1963. _ For some pipel ine proje cts, such as the TransAlaska Pipeline. all girth welds were radiographed . • By the 19905, the portion of welds inspec ted in this manner typ ically
ap~nes
I
1n'
45
~_1ODII_
'-ogoo
'._
_
CV') 'f~~_oo
... " _ " _
GIRTH WELDS: Inspection using ultrasonics
. We inspect new girth welds by:
Transducer ("probe')
e x ray (most popu lar)
. Ultrasonics _ Sound waves move thr ough the inspect ed material . • Normally they follow a straight line. but when they hit a defect, the sound waves are reflected . _ The operator of the inspection system can read the cha racteristics of the defect on a screen
23
GIRTH WELDS: Cracks
. Most welding standards require cracked" welds to be cut out
_ _ _ _ ..-d_"'"9'I.0 g
_ c,..... ·_
GIRTH WELDS: Acceptance Levels •
All wel ds contain defects. Therefore , we lding standards allow some oet ect s.: • Am eri can , Canadian and European Standards for Girth W elds allow sim ilar levels of defects.
• These levels are 'w o rkmanship' levels . •
O ld welds can contain de fects mu ch lar ger
nJ- ·1 root
---4--
I'
,
r-
than these workmanshi p levels. •
We know that these defects are usually insignificant because they have not failed .
"
24
GIRTH WELDS: 'Workmanship Levels' •
Defects in girth welds are usually assessed using the weld fabrication code/standard.
•
Th ese codes (e.g. 8 S4515. API 1104) allow some 'planar' and 'non planar' defects.
A PI 1104 8 514 5 15
• non planar defects are slag, porosity, etc ., and • planar defects are lack of side wa ll fusio n, etc.
•
Non planar defects are not usually a problem , but indicate poor quality, and they could mas k the presenc e of more serious defects.
•
Planar defects can act like crac ks, so we do not want large planar defects present.
•
All welds will conta in some defects, so the codes allow a reasonab le level of defects to remain.
o_xa-.t.',
"
GIRTH WELDS: 'Workmanship Levels' • Typical workma nship levels are :
• 25 mm length for defect s on the weld surface • 50 mm for defects embedded in the weld • Cracks are not usuall y allo wed ; cracks can indicate bad welding. poor material, poor quality control, etc.. • Cracks are usually repaired.
50
25
GIRTH WELDS: ' W o rkm a n s h i p Levels' •
Sometimes we have defects in our girt h weld that exceed our wo rkmanship levels
•
If we want to avo id unnecess ary and expensive repairs, we mu st use 'fitness-for-purpose' methods to assess these defects.
>25mm
• UK, Ame rican , and Canadian codes specify and allow their use.
• as 79 10:1999
give s fitness for purpose methods
•
0
BSI 7910 EPRG
T he 'EPRG' have pub lished the most complete set of 'fitness-for-purpose' defect level s for girt h welds . _
___"_0
51
GIRTH WELDS: Summary of Defect Assessment . You ca n assess defects in pipeline g irth welds using either:
Workmanship Standards
or
Fitness-for-purpose Methods
I
I
e.g API 1104 or BSI4515
e.g. BSI 7910 , API 1104 , 'EP RG'
•
wa SI 7910 IS a comprehensive fitness for purpose document - giving procedures for the assessment of defects in mos t structu res . _ 6 517910 details specific guidelines for defects in welds. Wit has an appendix (informative) for pipelines and pressure vessels. _ This appendix directs the user to the 'EPRG Guidelines' for assessing defects in pipeline girth welds _ The EP RG Guidelines are based on analysis, fu ll scale and model testing _ Considered 'state of the art'. _ Adopted in AS 2885.2
2,
GIRTH WELDS: Strength of Girth W elds with Defects
53
GIRTH WELDS: Defects in ' Old ' Girth Welds •
A European onshore gas pipel ine operator inspected 68 we lds in an 18" pipeline :
% UNACCEPTABLE TO
GIRT H WELDS
CUR RENT CODES Fab ricated Before 1968
70
Fab ricated Between 1968 and 1972
10 0
Fabri cated After 1972 •
Clearly, older girth we lds may contain unacceptable defects . • These welds are unacc eptable to workmanship standards, but they are not necessa rily unfit-for-pu rpose.
•
Clea rly, ther e is a need for detailed fract ure m echanics ana lyses to determine the sca le of this type of probl em , and avoid unnecessary repa irs.
C PMspon 2006 Ro,611
GIRTH WELDS: Defects in ' Ol d' Welds DEFECT T YPE
NUM B ER DET ECT ED IN 68 WELDS
Root Concavity Incom plete Root Fusion
245 177
l ack of Root Fusion
107
Cracks
79 1,743
Total Defects (pla nar and non -planar)
A ll the welds w ere tes ted - full scale in tension
!.",.'J
MOSffailed at > yield. But some we lds containing CRACKS failed at stresses bel ow yiel d .
1D_2006~
GIRTH WELDS: Defects tested in Bending
• •
.• .,•
• •
,•
• Pred icted using Kastner Equation
"I· - p(l - oJ) P 'pr + 2sin p(l- 'I)
• -..:?-~ • ._-,-----; Cl
0.6
u,
;; 0.4
~
PR, p= 2,JJ
•
•
a
~ =I - t
0.2
OL-- ,,...,-_ ,,..,-_ -:-=_ ....,...,_ -:-: -- - ' 0.4
0.5
06
0.7
0.8
09
Pred ic t ed Failu re Stres s/1.15X$ MYS
1.0
•
p =3.R,
-------
--
56
28
- -- - - _ .
GIRTH WELDS: The ' EPRG' Guidelines
GIRTH WELDS: Basis of 'EPRG' Guidelines _T he EPRG published guidelines on defe cts in girth welds in 1996: . 3R International, 35, Jahrgang, Heft 10-11/1996 _ The EPRG guidelines give us a choice of three 'tiers' or levels of defects. _ Each of these tiers give differing sizes of 'acceptable' defects _ The user chooses the level he/she wants 10 use
Tier 3: Fitness for purpose Tier 2: Fitness for purpose Tier 1: Workmanship Levels
Bigger defects allowed 58
GIRTH WELDS: Basis of the 'EPRG' Tiers TIER 1
TIER 2
TIER 3
PLANAR DEFECTS'
BS1 4515 AP111Q4
WIDE PLATE TESTS
FULL SCALE TESTS
NON-PLANAR DEFECTS
BS1 4515
BSI4515 BS17910'
BS17910' FULL SCALE T ESTS
INTERACTION CRITERIA
BSI 4515
BSI4515 BS17910'
BS1 7910' FULL SCALE TESTS
ACCUMULATION CRITERIA
BSI 4515
BSI 4515 BS1 7910'
BS17910' FULL SCALE TESTS
"Cracks are not allowed
°8 $ 1PO 6493 was used . which is now a SI 791 0
'wide plate' - -
C_:ll105-.
59
GIRTH WELDS: Basis of Tier 2 •.. 'Wide Plate Tests'
W"",,,' " -.., _ ..-.... ..,.<1 GO"l _"""".., d
eo "'" 00<7>0
3C
- --
-
-
-
--
GIRTH WELDS: The ' EPRG' Toughn ess Requirements _ EPRG guide line s require a toughne ss measured in Charpy V for TIers 1 and 2. and 'CTQD' on TIer 3
_Tier 1 and 2 require Charpy of 30~
11..
....
(min), 40J (mean).
_Tier 3 requires crou of O.1 0mm (min), O.1 5mm (mean).
•
RecenI _ ·' I~dGent shows_ v"'lO be_\lYe:
_ Denyl I'IaS_ _ h _ 3O/4(IJ Iimts ,., be equr..*'!", 002901l.053rm> ClOD. noIye1 beer1ll't""b". EPR G
- _ ·._
_T_ _ .. _ _ ._. _ _
R.-_·._
"
_.~'-'"'--
GIRTH WELDS: The 'EPRG' Guidelines · TIEIl 1 (nolo ' .1
1\'PO011I. """ ...."t
,- .",
--_
'/'10M IJlocl
"
••
......
gft_.
r....
- ""
"""-......... .... ----_. --~ , ,
_
..__.. .._...-"'_._I.. . ___.
-..
•
--
~-
~,
,010 ......
<~~
_ ,_C"'..,-........._'-. __...
YS(_l > YSlppe)
I VII~I $OI6
m(f'lpeJ~G.liO
__ _~C1!i"lo
~,
"'-............".
100"4 non--'"
~ E . . . . - w > I I e - A s s e s s m o < o :ECo\) (
_--d
............. •
~
S_'V
...,.be_
__ _ _ "" _ _ _ _ _.'"
--..,.-.o~_ce N_API 1 'OO.0I8S1.5 15_r-
n. _ _
crcc c,_ _ »O.l~ .....
~ (SUTS)
IT
,-
I
CTOO
,~,
T_ eon l>o......, _ 1Iy 1lpOCIOI _ _ 1 O _
.~-
~,-
OOJ
"'"""" > 30J
...... >_ _ _ _ _
~ ,
y ...... _ -
•
~ 3 """ (""'IliO' _ ""')
Clefoct> . - t>e Ire...., •
rdCTOO_Iot .......... a1 m ..........
s
.~
7 ~ h 25 . 4 m m
~ ( "'_ »
crcc
TIER 3 In ol o!>.)
I
"""_ tM
S..-taeob
"-
'-
llER l
1 ~ h 2 5 . 4 i<;..,....
•• •AS 2885.2 extends the Lise of r I8l' 2
to X80 and wall thickness down to 5rM'l
62
31
GIRTH WELDS: The 'EPRG' Guidelines
•
External Pro file
Tie r 1 Tier 2 l ~ er 3 AcceDtance criteria Limit c riteria limit c rite ria Excess weld metal should be uniform and not more than 3 mm in height. It should ITIE!fge smoothly with the parent metal, and not extend beyond !he original joint preparation by more than 3 mm on each side . No area should have the weld face lowef than the
In tern al Prom.
a(f aeenl surface , The root bead or any ooocavily should merge sll'lOOlhly into the adja ce nt surface but at no poin t should the weld be thinner than the
Type of Deleet
'i Oe thickn ess
Rool Concavi ty
Leng th
25% weld circum ference
Total
1.5 mm or 0. 1 I (le s se r)
UnderClIt ell
Len Ih SOmm To ta l 50 mm in any 300 mm or 15% circumference
Undercut root
L
less en h 25mm T""" 25 mm in 300 nvn or 8% circumference Dopth , mm or 0. 1 I (lesser)
ressee
Undercu t (Cl p,
~"
'" 7 xl inany300mm
Fi ure 1 Fig ure 1
r«t
F' ure 1 Figure 1
7x tinany300mm
assumed 10 be < 3 mm
•AS 2885.2 reduces embedded defeel eeeeceeoce \eogths 10 25mm lor t<7mm
63
GIRTH WELDS: The 'EPRG' Tier 3 cracks ar~ not permitte d
{
- , -y-;'--
TOTAL ALL DEfECTS
-
-
-
-
-
-
---t
( ' TOTAl. ALl ~AA DEfECTS
~ INDIVIDU Al. PLANAA DEfEC TS INTERACTING PLANAR DEf ECT S o L...~~~~~~~~~~~~~___J
1
1
9
10 11 12 13 14 15 11 11 11 19 M 21 22 n
~
25
Mini m um or mlla $ured wad thlck ne$$, t, mm
32
GIRTH WELDS: The 'EPRG' Tier 3 " r--~--~-~~-----'--------' I
r- TOTAL ALL DEfECTS (m aximum W ':'.)
(
2c_3.912t+O.3 12
!
TOTAL ALL PLANAR DEFECTS (maximum 25%)
2c"2.183t-3.383
I
I
INTERACTING PLANAR DEFECTS (mUimum 2S'kj
2c ·l.490t -l.133
c 7
8
9
10 11 12 13 14 15 16 17 18 19 M 21 22 23
~
25 65
Minimum or measu red w all thic kn ess, 1, mm
GIRTH WELDS: Using the 'EPRG' Guidelines
E ..
,
I
Hk @ ~ . .
-.
...
•
AP I, eSA and BSI all give guidance on pipeline girth ~ ': , " " _ ,... ......' " ..." ". "..........0"..... weld defect limits, but the EPRG gu idelines are well validated aga inst recent test data. and they are easy to use.
•
EPRG LIMITS: 1 can be used as the welding specification, Tier 2 as a concession, and • Tier Tier 3 when there is a big problem! The Tier 2 or 3 limits of the EPRG guidelines would not genera lly be • specified at the construction stage in a welding specification; modern girth welds should easily meet current workmanship standards. that the new limits in the EPRG guide lines be used for: • Recommended • special applications where longer def ects are anticip ated (e.g . new processes) • as a concession by the pipeline ope rator (in conjunction with pena lty clauses) to avoid unnec essary repairs" • as an insurance policy for cases where a defect is detected during postconst ruction audit or during in-service inspection
I> P""..- 2006...."' ,
"Two projects in Austral ia in the eany 2000s would have saved SAl million and $AO.75 million if Tier 3 had been used
00
GIRTH WELDS: Arc Strikes •
An arc 'strike' can cause an arc 'bum '
•
Arc bum s are localised melting of the line pipe, prod uced by arcing between an electrical contac t and the line pipe
•
The y can cause: • a small depression in the pipewall . • an area of local hardness • hardened layer may increase susceptibility to environmental cracking'
Me"n depth" 1,36mm Max length · 2.4mm Hardness can be >500 HV (WTlA TN32)
• on thin wall line pipe , the ha rdened zone may exte nd through the wall and increase chance of Hie on interna l surface, • possibly small cracks.
GIRTH WELDS: Arc Strikes Assessment & Repa i r •
We lding codes and regulations requir e arc burns/strikes to be removed, e.g. by grinding. However:
•
The y are generall y not considered a problem" . if coated : • They do not cause service failures" • The area hardened/cracked is very small and insignificant
•
But it is good practice is to grind them away_ • Ensure lhatlocal wall thickness is not reduced below minimum spec ified
-._
__ _
Grind depth and length shou ld not exceed limits in
-___ -_...._.. . __ ,........ _. _.___ .. __ _. _... ..__ --_..u_.... -,._--.-_.. .. _---..----A$ME 831G _
~
.
ooo _ " " ~ _- "' _
-0"' - - ??
.. """, .
"", .. - . -_ _ ",.--...
,~
....
68
3~
GIRTH WELDS: Additional information
69
GIRTH WELDS: FATIGUE DESIGN
_ l(_S_ P~-o.-..kl f_o.r
7lI"IrOCI:d OWA£Ot,
()IO.r-
__
" ~ ~" _' .
E...--r. _:DII . .... ... _ - .
T.&l• .... - . . . . ..........
.
3
GIRTH WELDS: FATIGUE DESIGN· Historical •
Fatigue is not usually a prim ary concern in trans missio n pipeline girth welds .
•
Some offsho re pipelines (e.g. at spans, or deep wat erlfloating structures) can experience large axial stress cycles , and also offs hore pipelines can be heavily cycled during laying.
•
We ca n assess the fatigue life of a weld in two wa ys:
• l iquid lines do pressure cycle. but this has small effect in axia l stress direct ion
• 'DEFECT-FRE E' · We usually assess the fatigu e life of a weld usin g 'S- N' curves, where we 'classify' each weld acc ord ing to ns shape and process (Class 'A' has high fatigue life, 'W 'low). • DEFECTIVE - If we have a defect (in excess of workm anship) in the weld we cannot use S·N - we have 10 use fracture mechanics, e.g. 887910.
•
The following slides pre sent the 5-N approach , the refore we are assuming a good qual ity weld, with no significant defec ts , or defect s in excess of recog nised standards (e.q. 854515 or API 1104), operating withi n desi gn conditions. 71
GIRTH WELDS: FATIGUE DESIGN· Historical •
Girth welds are usually 'single sided' (made from one side ) • We know that the condition of the root of a weld, and any misalignm ent h a ~ -;:-~~~~~~_ _ ~~~ major effect on fatigue life ('N'); '" there fore , g irth we lds have been traditionally classified as sim ilar to fillet welds. This is a severe classification , a nd leads to : /' • Class F f()( single Sided girth we lds madeon a permanent
1
-=-
t' '.
backing strip • Class F2 for single sided welds with no backing strip (I.e. ass ume s pos sible poor root and misa lignment)
-r-t
-=
~',
..
= '":'~~__.:::=::::~~=:J .. " a ... . (
L
• There is now evidence to show that >0 these welds have good quality roots '" and mis alignment can be contro lled .
'
End...- . ....... .
n
31
GIRTH WELDS: FATIGUE DESIGN - Recent Data •
Recent data on single sided girth we lds (up to 16mm thick).
•
A ll the results are above the F2 line , and Class E looks a reasonable classification provided full root pene tration is achieved . Most girth we ld fat igue data is confidential, but it has been reco mmended' that: • Use Class F2 but do not indude stress magnificat ion factors (SMF) for misalignment
•
•
•
Fatigue fail ure always initiated at the fool
Use Class E but incl ude allowed under fabrication the misalignment (e)
.. ~~~~:-~--~-:{::::~{~1 Specificationsf"' _ -) \-0
• P\ale misaligrvnenllotmuloo are in as 79 10. bullhese may be conserva live due 10 !tie constraint 01 tt>e sheI
struo::ture. AIIemativeIy._. • SMF . 1+(3(aIl)elql(-{0JI)"'''n
• D . diameter, I" wl •
1 f .• •
••
Girth we lds 'With temporary
backing can be consideredClassE
..'.
.• _ o.l._ '. '-'.R R_", '_ I- """,,",R _ ·'._ .'. ' •C_ '_ .R. ,R.O......__ ... ·,. ,''''
•
E ""~'_ . ~
73
GIRTH WELDS: FATIGUE DESIGN - Guidance' •
The design of girth welds using S-N data assumes failure from Ihe weld cap or root •
They do not cover fai lure from identifiable de fects. • Such defects (e,g, in excess of workman ship limits. or surface breaking crack.like naws) can reduce fatigue life. Example acceptance levels /of noo-planar defects are (BS 7910): Dni . 0. ..
,, D
,.
G
,, " ' ,,,
- - hldl'>WoI ~p
·- ~." _ 01 __ """ ·
•
..
•18.. oce Un« l i mi • I' . ...... ~ " % . n • rod'
• ""'.t. .
Slot ind •• ;o. knfllo, nll n
l ' _....'"
•" " "
O.O2} OO~
O.OJ}
""
p.;., l _
_ _ _ of.~".._
1"",,
Guid ance can be given for the follOWing range of Pipe geometry
_
_.-.._--,.,,-""""' ... _,-,-""'" .........
"'... _
.. _"'"' ...... .v
or.I.WI'''''''H'''
~""""""
.......,
~.:=
,"""'-_. \10". >1,
"",,,,,,,,""<1"-
.,.,-
......1•
:,",,,":5am
00
x·..
' ·Oll'.'..... ....-..·........'_I........ ,.;,j·
....·...........M) """" • on", , - ~. II "" ,, _
F.. ,Pf
f.,',., ....""" ....... ~ tom " ' I............' ,,'oul
...........'..,'. ("1'
3
GIRTH WELDS: FATIGUE DESIGN - Guidance · •
The proposed guidance is:
* = 1" (3(efl )exp(-(OIl ,-oS]1 _ 0 = diameter. I z wt "s
~;;;:;:::;;::::::--'~~;;:;:l - . - ""*""'"
._c.... .-c: . _"'. ._ H_Q)
(SW ' CPI
~,=, ~,~o ~!t.:.~~...- ~=;..s-::P
. '1(",' ;5
_ C UI\If! S are for 1<16mm . ~ _ lrJCfeasing thick ness ca n .; dec rea se fatigu e life. '" _ If 1>16, the stressrange Ii obtained from the SoN :;
curve should be multiplied: by (161t)'l '5 ;;
'.
- . . - . - -. • •
-,~,aO-. '. ' _,.~.",,- ' O. '
-----------------c...gnS .. c
ol
""',"''' $"' ..".....
•
g~~
_ e is m lsalognmen t
D'1.00PSWoO' [)'1JXPSf;-<:P
. 11''''
' 1''SlP
- . _-"'_.... _-_-----_ .-_,....,
•
,,.
_
_
--
""-- ,
~ ~:;~'~I,
J
S('h10"
J
1,11401.
S J
5 3h I." :.~ . ,o"
" "Cll'6" o'
'''''RP
--
.... ,.(W. ,,'
', 00 . 10" ,N . HilS,
' l ' . .o"
En ,.p ' n."p Sw>cp
"'U".,-
. ........ ' ''''.['1' .... ...
S ~:lol . ' O: .. . UI2S " r1
'1'I'1'',.:loIPSW..:P :lOP ) :I ff1 .:MPSW
... """",,-,- o _ P _ _ ...
~,.. .. .....
c.. ..... ....... .l:., • •.t
1ft
'"
,,.
"
Enduran ce, cycl es
PIPELINE GIRTH WELDS: Welding Informa t i on
zs
3,
PIPELINE GIRTH WELDS - Line Pipe Grade . When weld ing grades of steel up to X65, the normal procedure is to use a 'manual' - shielded metal arc welding (SMAW) - process , with cellulosic electrodes running in the vertical down direction . • The higher strength, pipeline steels , particularly the X1 00 grades, cannot be fully welded using cellulosic electrodes during welding, since the large amounts of hydrogen generated by these consumables during welding can lead to hydroge n cracking of the high strength weld metal. e c onseouenuv a change has to be made to either low hydrogen consumable for SMAW welding , or the process must be changed to gas metal arc welding (GMAW) or flux cored arc welding (FCAW) . 0
_
77
PIPELINE GIRTH WELDS - Direction .Downhill weldi ng _ Downhill welding by cellulosic or low hydrogen electrodes is applied because of high efficient welding as high currentand high welding speed.
_ Downhill welding can be applied to all passes. _ This method is most competent for welding of large diameter (more than 254 mm).
• Uphill welding _ Uphill welding is lower efficiency because of low currentand low welding speed. but the quality of the weld is much better than downhill welding
78
3\
PIPELINE GIRTH WELDS - Pre & Post Heating . Preheating . Generally it is unnecessary for line pipe (mild steel) to be preheated _ it is necessary for thicker pipes . high tensile strength stee l pipes and low alloy steel pipe s to prevent hardening of the heat affected zone, and cracking .
• Post weld heat treatment (PWHT) . Pipeline girth welds are not PWHT as they are usually thin walt" _ It is usua lly unnecess ary to post weld heat treat ('stress relief ) pipes and line pipes . unless (see ASME 6 31.8): _ The steel has carbon content> 0.32%, or e c arton equivalent of 0.65%, or
__ 010:III_'
_ Thickness' >1.25"
--..---- ---
_. """-----......... _-"' . _- --,... _---,..... ...- . s _ O_ _ •••
.. _ _ .._ .
.~.- -~ ---'"
GIRTH WELDS - Electrodes: Types
a c enutosc electrode _The welding speed for rool pass of cellu losic electrode is 20 to 50 em/min., which is high speed compared with other types of elec trodes.
_ Low-Hydrogen Electrode _ The welding speed for root pass of this type is 15 to 35 em/min, which is slightly lower than cellu lose type . _ However the deposition rate of low hydrogen electrode is equal or more than cellulose type _ _ This method has good crack resistibility and high efficiency
0_2*_
4C
GIRTH WELDS - Electrodes: Classification _ Consum ables for shielded metal arc (SMA, or manual metal-arc) welding have an AWS classification
. For example, E6010 or E7018·A2 : _ E· just means electrode, a First two (or three , in case of 5-d igit spec) digits describe the UTS of welded mate rial, in ksi, a third dig it describes the we lding positions possible. 1 is all-position and 2 is flat and horizonta l only, a fourth dig it describes something about the coating co mpositi on and its
effect on weld characteristics.
"
PIPELINE GIRTH WELDS - Residual Stresses . Pipeline girth weld s wi ll contain 'residual' stresses' _ These are stresses created during the welding's hea ting and co oli ~g process e 'r nese stresses can increase with increase in the welds size and lor thickness _ They can be redu ced by 'post we ld heat treatment' (PW HT) . Pipeline girth welds are not PWH T as they are usua lly thi n wall _ It is us ual to assume a level of yield strength resid ual stresses in a weld that has not been PWHT _ In single sided girth welds, it has bee n shown that residual stress es at the root decrease and may become compressive as thick ness increases above 25mm- .
O_2OOlI_
.
_--_
_._"---_.__ _--,.-.. _-- ... _..-..
82
41
GIRTH WELDS: Defects
~
\i~~ ~
frcorrplele Joint } Penetration 83
ERW LINE PIPE - Managing Integrity of Old ERW lines
..
ERW LINE PIPE - Managing Integ rity of Old ERW lines * - Assessment Plan Overview
-- -Dec iding if an ERW Seam We ld Integrity Assessment Plan is Needed
•
-= •
~''-----.;
•
•
--
.,._- _...__ __ . . ... _- '... _ -_. -.
85
ERW LINE PIPE - Managing Integrity of Old ERW lines · .. Do I need an Assessment Plan? _ Step 1: Do I have a problem pipeline? a con sloer dia meter ; W.T.; grade; age; ma nufacture r; MOP; hydrostatic-test history; service failures; in-line-inspection history; coating type; CP history; • operating pressure cycles ; type of product: seam type (low-frequency. elc.?) . • Age alone ca nnot be used to determine if a plan is needed, but it is a consideration. _For example, a 1940s-vintage pipeline may warra nt an assessment if it is subjected to agg ress ive pressure cycl es or if it is fou nd to be significantly affect ed by corrosion-caused metarloss. _ If yoo have modem ERW , or low pressu res , etc., you wi ll not need a plan
_ Step 2: History of service failures resulting from seam-related problems. _ If a fatigue-related failure , or groove corrosion failure has occurred after the line had been tested to a pressure level of at least 1.25 times the MOP, a seam-integrily-assessment plan should be developed. en the line has no recorded seam- related serv ice failure, or any seam -related service failure is explicable as a non-time-dependent event, the plan is not necessary O~2OOlI _'
--_-----_ " "- _.... _-_.
..
...
86
ERW LINE PIPE - Managing Integrity of Old ERW lines " • Do I need an Assessment Plan? _ Step 3: Pressure Cycling . Is the MOP relatively hig h (50- 72% SMYS). intermed iate (30-49% SMYS). or low (<30% SMYS)?
.....
_ How severe is the pressure spectrum?
""'"
_ Agg ressive ness of pressure cycles can be crudely categorized for particular environments as shown in the Table opposite.
.-,.., es, n
..., .........
... "
~
"
~
,'" "'"
-
-
-~~
" "
..
zso
,
...... ,
•
~"'"> " ;,';;.<";;'
.
"' .~ ~
I as-as _ If fat igue failures have occurred , \, .\)~ or if the pressure spectrum falls d'* into the aggressive or very aggressive category, a seam-integrity assessment plan should be developed .
'"
,..
'"
_ If no failure invotving fatig ue crack growth ha s cccorree. and its pre ssure cyde aggressiveness can be shown by ana lysis to be inca pable of ca using the margin of safety demonstrated by its last hydrostatic test to be eroded within twice the expected life of the pipe line, no plan is needed .
--_------_
..
...
_-__-_. ....
"
ERW LINE PIPE - Managing Integrity of Old ERW lines" • Do I need an Assessment Plan? _ Step 4: Test Pressure _The te st-pre ssure history of the line should be re viewed. _ Any in-service seam failure s (leaks or ruptures) that occurred we ll be low 1.2 5 x MOP, or belo w the level of a previous test need investigating . _ TtIeY could be fatigue-enlarged defects Of selective seam corrosion. _ The causes of all l est breaks
Of
lea ks should be determined
_ If the test failures are due to time-dependent defect growth (fatigue Of selective seam corrosion). an assessment plan should be developed. _ If hook cracks or offset skelp edges are revealed by test breaks but no evid ence of fatigue is foo nc:l, the pressure cydes on the sys tem should be reviewe d 10 see if fatigue cou ld become a problem. _ If the pipel ine has no test breaks when tested 10 a pressure level of 1.25 x MO P, it does not require a plan .
.
~--
e u breaks occurred at test pressure levels »1 .25 x MOP, and large pressure re versa ls are extremety unl ikely. it may not be nece ssary 10 have a plan .
,-._- -- -- _.._--
---- '
. 4'
ERW LINE PIPE - Managing Integrity of Old ERW lines· . Do I need an Assessment Plan? _ Step 5: Corrosion _ A pipe line with a known serecuve-searn-co rrcecn problem req uires an assessment. _ A ba re pipeline , a pipeline with poor coating . or an extensively disbonded coating cou ld be a candid ate, _ If extemat or internal corrosion is found, the potential exists for selective seam corrosion.. _ ERW seam made before abou t 1980 may be more susceptible to selective-seam corrosion. _ If the operator is confid ent that no selective-seam corrosion is occurring, no plan is needed _ Transporting only non-co rrosive products ensures that no internal corrosion can affect the seams.
--
,' _. _ - - - - - ~ ""' - _. _
. _.. _.
89
4~
Fracture Propagation and Arrest
Penspen Integrity
1
...". """'_ _'.. .. __...... "'"
FAI LURE BEHAVIOUR OF PIPELINE DEFECTS • •1"...."""""" "..
Part-W all Defect
""'.
~-.,
PAAT·W'"-'-"".ECr ....
... ".. _in. Thr ough.Wall Defect >
...... ,... OUC...w ..... DEfECT
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g. .... r~ROIJO><.w .t"" "...,.... ~ -.
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Prop agates
_""'.,""'''''I''.....
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,
_
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An-lists H9"..-
FRACTURE PROPAGATION IN PIPELINES ' •
In the late 19S0's/early 1960's the re were a number of long failures in in-service pipelines , e.g.: •
•
in 1958 a 26 inch Venez uelan gas pipel ine fro m Anaco to Cara cas suffe red a 5.6 km (3.5 mile) brittle fracture, and; in 1960 Transwestern Pipeline Com pany 30 inch, X56 pipeline suffered a 13 km (6.1 mile ) britt le fract ure
~~~
,
C_ 2CJ05 _,
TOUGHNESS IN PIPELINE DESIGN CODES/LINE PIPE SPECIFICATIONS
•
•
•
Pipeline and line pipe standa rds often specify a 'toughness'. W hy? Th is toughness is usually in term s of 'OWTT or 'Charpy'
~
W e need to spec ify a level of toughness to ensu re a 'running' fracture will be 'arrested'
DNV OFFSHORE PIPELINE DESI GN CODe <=30mm
Wall Thick ness
Outs ide d iam et er (mm ) <=6 10
1<=820
1<=11 20
Charp y Tough ness (J)
SMYS
245
40
4.
4.
290
40
43
52
360
50
61
75
415
64
77
95
450
73
89
109
485
82
100
124
555
103
126
155
,
TOUGHNESS & FRACTURE PROPAGATION •
T OU GHN ESS - Tra nsm ission pipelines must have sufficie nt tough ness to arrest propaga ting fra ctures. • Specifyi ng an adequat e toughness 10 ens ure the arrest
of propagating fractures is a desig n cons ide ration.
•
SCOPE · Crack propaga tion is a problem in pipelin es co nveying gas or liquids with high vapo ur pre ssures, NOT liqu ids.
GAS OIL
• We do not ap ply crack propagation tou ghness limits to welds
_--- ""'---_ _-
_ _ ..
~
...
cw _ _ ,
.. _
...
_
s
.
TYPES OF FRACTURE PROPAGATIO N •
•
•
T YPE - A propagati ng fracture is desc ribed as either brittle or duct ile , depending on the fracture Toughness mechanism (this can be (Energy Absort>ed In Test) determi ned from the appea rance of the fracture surface). EFFECT - Both types of fractu re propagation can result in fractures extending for long distances . CONTROL · Crack propagation is cont rolled by specifying minimu m toughness requirements .
_---- ---_ _
__ ..-.. __csu....-._ ,_ _ '- .._ ....
.....
...... . _-..
Low Tou ghness Defect Stress
TRANSITIONAL
Tempera ture
_
s
'DUCTILE' & ' BRITTLE' BEHAVIOUR: DWTT
-------
' DUCT ILE' & 'BRITTLE' BEHAVIOUR: Charpy
0_2'001I_'
,
IN·SERVICE FA IL U RES • Brittle Crack Propagation • 1960. New Mexico, USA· brittle fracture • extended for 8.1 miles (13km) in a 30in. X56 gas transmission pipeline of the Transwestem Pipeline Company.
13km
• Ductile Crack Propagation • c. 1970s. USA - ductile fracture • extended for 1864 feet (56arn) • in a 16in., 0.219io. wall thickness, 5LX 60 ERW gas transmission pipeline .
O.57km
,
BRITTLE FRACTURE PROPAGATION CONTROL Basic Concepts Crack speed
•
Brittl e fractures propagate at very high speeds in excess of the speed of the decompression wave of the methane gas (400m/sec (130OfUsec) • the tip of the runni ng brittle fracture will expe rience the full press ure existing in the pipeline at the time of the incide nt that caused its initiatio n, as the gas cannot 'exhaust' from the pipe at speeds highe r than the acoustic velocity. • Arrest occurs when the fractu re speed is less than the decompression speed • We find that the lower the temperature of the pipeline. the faster the fractu re speeds • So. we need to ensure that the pipe line is not a brittle material.
O_2(g_
"
,
DUCTILE FRACTURE PROPAGATION CONTROLBasic Concepts
•
Ductile fr act ures run at lower speed s; • These can be below the speed of the decompres sion wave. • Hence, the first requirement in preventing any running fracture in a pipeline is to ensure that any fracture will be ducti le • However, despite travelling at speeds lower than the decompression speed, it is possible for ductile cracks to propagate indefini tely because of the nature of the decompression process. • This is because the gas expanding in the bulging pipe imm ediatley behind the crack tip provides energy to propagate • So, we also need to ensure the ductile pipeline has sufficient TOUGHN ESS to arrest a running ductile fractu re tt
THE CONTROL OF PROPAGATI NG FRACTURES •
1. Specify a minimum toughne ss requirement to ensure that brittle fracture propagatio n does not occur. E'*\ly A_ I.g~..,.,.."....
->
•
2. Specify a minimum toughne ss requirement to ensure that ductile fracture propagat ion does not occur.
•
Alternatively, specify a minimum toughness requirement to control the length of a ductile fracture, i.e . reduce BRITTLE the probability of a fracture of a given Tempe rature length to an acceptably low level (e.g. a 5% probability of a fracture 3 pipe lengths ). The acceptable length will depend upon operational and maintenance considerations.
0_2006_'
DUCTILE
"
(
CHARACTERISTICS OF RUNNING FRACTURES IN PIPELINES 800 - 1500 Ips
400- SOOfp$
>1500 Ips
Fracture Speed
Fractu re Appearance DlJctile Shear
Mixed Fracture
r
'6 Fracture p atterns 1 «2 Paths
1 Crack Path Arres l Possible
__
Multiple Paths
-"""''''"' 'So'W _ _ at _ _
lB&.a"-.E"B V U , _ , , - e - . c : o r - _ eo:
"
~_T _,_'_
Fracture Speed Versus Fracture Appea ran ce Data from Full Scale Fracture Tests 3000 11
-"
30" x 0.375 X52
~2500
.
•
•
•
: 2000 .1 ' •
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(J)
CD
•
1500
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1000
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o0~--:2:':0'----4c:'O::---'6LO-----'8:':0--Ic:'OO Full s core Fra ctu re App earance. % SA O~
2008
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BRITTLE FRACTURE PROPAGATION
rs
BRITTLE FRACTURE PROPAGATION •
Exten sive brittle fracture propagation occurs because the speed of a brittle fra cture is greater than the speed of the decompression wave in the ... gas (circa 396 ms-t (1300 fts .' ) for me thane ) • The crac k tip therefore sees the full line pipe pressure and so can propagate indefinite ly
--
•
•
Brittle fracture prop agation is driven by the elastic energy stored in the pipeline wall (a function of the applied hoop stress) W e ensure a pipeline does not have propagating brittle frac tures by measuring its toughness using a The 'Drop Weight Tear Tes t' (DW n)
THE DROP WEIGHT TEAR TEST •
The drop weight lear test (DWn) specimen is a full thickness test specimen with a 5 mm deep pressed notch in the centre of the span.
•
The spe cimen is fractured in a single impact by a falling weight and the % shear area is evaluated in the central portion of the fracture specimen.
•
This type of specimen is
specimen.
'''''"' . ...'
0
sometimes known as a pressed-notch own
p"_._.r J'--a_ ""lIuated;" cenls1l parl of
-'---- !-7"'-----"-==--r"<~
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A
t. "
BRITTLE FRACTURE PROPAGATION •
The DWn specimen is an impact specimen, so we can measu re the energy absorbed in the test
,~,
aema Energy abso
"
BRITTLE FRACTURE PROPAGATION •
The Dw n specimen is also inspec ted after the test, to de termine its 'shear area ' or '% duct ility'
•r o ;
-
-
-
' 00
----'
Temperat ure
C_200S_
"
BRITTLE FRACTURE PROPAGATION •
The ow n characterises a material's resistance 10 brittle fracture
Energy Absorbed
%Shear Area
o
propagation. •
The percentage shear area of a DWn specimen (or the transi tion temperature) is related to the toughness of the steel.
DUCTILE
• Experiments have shown a correlat ion between transition temperature and fracture speed . and between
own
the shear area of a DWn specimen and the fract ure speed . •
Therefore DWn models full scale behaviour
. ..rna
.
" Temperature
We conduct our OWTTs on the line pipe . AS 2885 . 1 states that propagating brittle fract ures in Ioogitudinal welds (ERW or SAW ) have not been recorded in operating pipeli nes 10 dale. Plus. Ioogit udinal welds are offs et at girth weld s, eliminating a fracture path .
C>_2OOlI_'
10
---~~
---- - - - -
- - -- -
- --
PREVENTING BRITTLE FRACTURE PROPAGATION
•
Brittle fractu re propagation is prevented by specifying a minimum toughness to ensure that the line pipe steel is on the upper shelf of the tran sition curve at the minimum operating temperature, i.e. the fracture propagation transition temperatu re (FPTT ) of the steel is less than the minimum operating temperature.
•
The FPTT is normally taken to correspond to the temperature at which a DWTT specimen exhibits an 85 % shea r area fracture .
Energy Absorbed Of % Shea r
I ~ne 85 %
• This requirement ensures that the line pipe steer can not susta in a propagating brittle fracture.
Operate your pipeline abov e this te mpera ture
FPIT Temperat ure e_KIOI_l
"
DWTT FRACTURE APPEARANCE AND ' FPTT' DWTT MODELS FULL SCALE PIPE TESTS I
~
s:
0.9
...• a.a
ii •,
0.1
OWTT ...
". 0.6 ~
,
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0.3
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e
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FPTT: Fracture propagalion tralls.ition temperature
~
-30
Te~ af"r.
n:rement
-20
- \0
from rPH;
r
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11
PREVENTING BRITTLE FRACTURE PROPAGATION - WHY ' 8 5% SHEAR'? PIPELINE TESTS
D
D
0
•
0
• 0 0
D 0
•
o
0
•
20 40 60 80 100 % Shea r fracture .rea (DWTT, PN spedmeo) .I&!!!
Comparison of PN-DWTT end We sl Jeffe~on tnt res ults III Wesl Jeffers on t est temperat ure f or w all th icknes ses above 19 rom
---._ ....
..-..~- --_
owrr
_"'_ .... _-_.......
.. _-,...
DUCTILE FRACTURE PROPAGATION
DUCTILE FRACTURE PROPAGATION: Why? •
Ductile fractures propagate axially, usually along the top of the pipe
•
They travel slowly; 30D-900fUsec (91 274metreslsec).
• This slow speed allows time for: • the fractured pipe behind the crac k tip to bulge and cr eate a high longitudinal stress at the crac k tip,
• ovansanon of the pipe ahead of the crack, & elevated hoop stress
es
DUCTILE FRACTURE PROPAGATION: Why? (cont.) •
Therefore, ducti le crack propa gation is dr iven by: • the elastic en ergy sto red within the pipe wa ll and • by a transfer of energy from the gas to the crack tip by bulging immediately beh ind the crac k .
•
Hence, despite travelling at speeds lower than the decompression speed . it is possible for ductile cracks to propagate indefinitely because of the natu re of the decompression process.
~ -~ - ~~ -.ss
1,
DUCTILE FRACTURE PROPAGATION: Tests •
Since the 19705. the re have been a large num ber of full scale tests to investigate the factors that influ en ce propagating ductile fra ctur es. • Th e inv esti gatio ns ha ve relat ed Charpy V to ugh ness to the abi lity of a pipeline stee l to arrest a ductile fracture • This has led to a number of empirical and semi-empirical criterion fo r predicting the Charpy V-Notch impact energy necessary to control ductile propagation . reservoir
hig h to ug hn"n p ipe (to arN!sl)
low toughn ess Init i ator p ipe
high to ug hne ss pipe (to arr est)
reservo
THE CHARPY SPECIMEN •
The full-s ize Cha rpy v-notch impact test specimen is a specimen w ith a length of 55 mm and a square cross-section with 10 mm sides .
55mm
• A V-no tch of 45 degrees included angle. 2 mm deep with a 0.25 mm radius of cu rvature is machined in the centre of the length .
•
Redu ce d section (su b-siz e) test speci me ns are also defined , with a width of 6.7 mm (a 'two-thirds size' specimen) an d 5 mm (a 'half size' specimen).
FUU
l Omm
1/2
6.7mm
5mm
• The not ch is machined in one of the narrow er faces . We condud our Charpys on the line pipe. AS 2885 .1 suggests that propagating ductile fractures in longitudinal welds have not been recorded in operating pipelines to date. Plus. longitud inal welds are offset at girth welds , eliminating a fracture path.
ea
l'
THE CHARPY TEST •
The specimen is fractu red by one blow from a swinging pendu lum .
•
The (impact) energy absorbed is calculated from the difference in the maximum height of the pendulum at the start & end of the swing .
•
The energy is absorbed in the initiation and propagation of a flaw , and in the deformation of the specimen.
-
"
THE CHARPY TEST
••
~
• •• r"'"
• • •
0_2001_.
.
I
so
15
CHARY TEST: Effect of Temperature Charpy V-Notch Impact Energy Energy Abs orbed
upper shelf (DUCTILE) 100 percent Pipe line steels usually operate on \his 'Upp6f' she ll, afld so are ductile,
Percentage Brittle
Fracture
~_.. O.. percent
Temperature
CHARPY SPECIMEN BEHAVIOUR VERSUS STRUCTURAL BEHAVIOUR Energy Absor d
Str ucture (e.g Charpy Spec i men
_ - - 25mm th ick pipeline) The specimen may behave in a ductile manner (i.e. 0 percent
d eavage area ), but the strucnwe could behave in a brittle manner at the same temperat ure. Hence we n eed 10 CALIBRATE our small Charpy tests -Mth full scale behaviour
0_2OOlI_
Temperature
FRACTURES IN SHIPS (also in 'Fracture Mechanics' Notes) •
Ship hu lls used to be 'riveted together
•
In all probability, cracks in ste el hull plates of ships was com mon place. • Except that due to the riveted co nst ruc tion techniques of the era, a crack in a single plate was not catastrophic and would be attributed to an occasional single bad stee l plate from the steel mill or faulty fit-up in man ufacture.
• A brittle fracture, woul d only run to the next riveted jo int, typ ically not more than 20 feet in length, with notice able but not catastrophic leakage which could be co ntained until the next reasonable sc heduled repair.
FRACTURES IN SHIPS •
The 'Li berty' cargo ships we re welded structures, built in the USA during World War 2 to bring 'liberty to Europe'
-
• Out of 2700 li berty ships built to supply UK, 400 sustained fractures, 90 of which we re considered serious and 10 broke completely in two. • 1000 suffered significant failures between 1942-1946because of low temperatures, while 200 suffered serious fractures between 19421952 • The US Government knew something was wrong, because the failure rate of the we lded liberty ships were very high in the North Atlantic , while literally NON-EXISTENT in the warm waters of the South Pacific .
17
THE LIBERTY SHIPS
SdlenectiJdy, 1943 New ship F.,iled in h
on th e Liberty ship s in it iated a t poo r welds, not associa ted with design details
The quickest a Liberty ship was buill 5 days after the keel was laid!
THE LIBERTY SHIPS •
The Libert y ships are an example of wh ere the Charpy speci me n has been calibrated agai nst structural behaviour .
•
The Liberty Ships we re the first ships to have an all welded hull. A .. larg e num ber of the ships failed in a brittl e manner. The ship plates we re tested using the Charpy specimen to determine: • the plates whe re br ittle fracture initiated
• the plates where brittle fracture propagated
• the pla tes whe re brittle fractu re arres ted
"1.III•••11!1
1I!11!!~~III•••'
?
?
?
THE LIBERTY SHIPS •
The resu lts were : • initiat ion (sou rce) plates had an average Charpy energy of 7 ft Ibf
7 It Ib
• propagation plates had an average Charpy energy of 10 fI Ibf
10 It Ib
...
-=!!!!!~
• arrest plates had an average Charpy energy of 16 ft Ibf
•
Therefore , to arrest a fracture, a plate would need to have a Charp y energy greater than 16ft Ibf.
•
Also, design changes were made 10 remove local stress conce ntrations (they removed square hatch covers).
<
..
_ 16 It Ib
L
CI_2OOI_.
"
LINKING CHARPY TESTS TO FULL SCALE PIPELINE BEHAVIOUR: A Fracture Propagation Test reservoir
reservoir
in le rme d ialu toughness p;p.e
;nt e rme d illt. toughness pipe
test section (not to scala)
CI_2OOI_'
19
DUCTILE FRACTURE PROPAGATION TESTS FUll .ca l. bu",! lut. carried out in the last 25 ~ ....
DOth. " _ JI SI
!IJ Mann . Foo ll1ills
U
D EP RG · CSM
J
- SM I. Athe n.
ae su l[l eG ~A I S I
'" 19 75
1980
1985
'990
19 9 5
Y. .,
PREVENTING DUCTILE FRACTURE PROPAGATION •
The Charpy im pact energy is related to the ductile toughness of a pipel ine. • Minimum levels can be specified that ensure thai ther e is insufficient energy available in the system for ductile propagation to occur
•
T he arrest toughness is a function of • the pipe line geometry, • stress leve l, the pressu re, and • the decompression characteristics of the fluid that is conveyed in the pipeline.
•
Charpy Energy Absorbed (toughness)
Temperature
A num ber of emp irical and sem i-em pirical criteria exist to estimate the minimu m required arrest tough ness (e.g . Battelle, AISI, British Gas) . • T he formul a due to Battelle is probably the most com mon ly used .
2
CONTROLLING DUCTILE FRACTURE PROPAGATION (METHANE ·)
Battelle
5 C.. = 15 x 23 82 x l O- a;( Rt) lIJ
50% confidence
Alsr
CO' = 15 x 2.377 x 10-4 G'.li2(D)112
95% confidence
where
'Note that the presence d
= = = = =
C, a, D R I
phase 'dunng dec:ompres$iOn. See ASME 83 1.8
These are known as 'short' formulae'
"AS_'_ -.-...... _ _ _ $""" F
_
.. _
ott-
pentane, e lC.) in nalUflll gas, gives a 'rictl' gas.. These formulae are nol appropnate lor Ihese rid'! gases or when the gas ellhibb a ~ gaMS (ethane.
fu ll size Charpy V-Notch Energy, J hoop stress, Nmm-2 pipe diameter, mm" pipe rad ius, mm pipe wall th ickness , mm
-
"'__ &_.__
Spreadsheet?
_d~_"'
........ ""'
. . . 5 ........ -'.
...
OO
EXAMPLES OF CHARPY REQUIREMENTS FOR 'DUCTILE' FRACTURE PROPAGATION CONTROL •
Examples of Charpy formulae in ASME 8 31.810 arrest a ductile fracture in a gas line are : • Ballelle formula : CV N 2: O.0108cr2I 1IJ R 1/3 • Am erican Iron and Steellnstilute : CVN 2: O.0345 n31 2R '12 • R,t in inches, (J in ks i, CVN is 'full size' and in ft lb.
•
The Canadi an Standard, eSA Z662 gives:
• CVN = O.00036cr3'2R1/2 • R,t in mm , CJ in MPa , CVN is 'full size ' in J . Sma ll diameter, th in wa ll, or low stress pipe does not require Charpy toughness requiremen t. GSA Z662 co nsiders: . <114 .3mm outside diameter; <6mm nominal wall; o r design operati ng stress<50MPa . pipe as not requiring Charpy testing
o_aooe_,
"
21
.._--- _.__... BATTELLE 'SHORT FORMULA'
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DUCTILE FRACTURE PROPAGATION - More Complex Model - Theory •
THEORY - Ducti le crack propagation is explained as follows'
• if their exists a stress level at which the fracture ve locity and the corresponding pressure wave ve loc ity are the same, then the pressure at the crack lip will remain constant and the crack will propagated indefinitely. •
Consequently, the pr opagation of a ductile fracture can be described by the ba lance between the drivi ng force for fractu re propagation and the force resisting it. Crac~
dnlfingforce
TOOghneSSr""iS(j ng~====:':=:::====:' , e Ponoren 2006 "",,611
,... ",..
z:
DUCTILE FRACT U RE PROPAGATION - More Complex Model •
MODEL - The Battelle two-curve mode l (TeM) is a semi-empirica l mod el that cons iders the balance betwee n the driving force for fracture propagation and the force resisting it. • It can be used to predict the min imum toughness (Charpy V-notch impact energy) required to arrest a propagating ducti le fracture.
•
The reM considers the driving force to be directly related to the gas press ure in the plane of the crack tip.
• •
The r eM can be applied to rich gases. The r eMis expresse d in terms of the fracture velocity and the gas decompression velocity, as a function of hoop stress (press ure). Crack d<;v;ng force
Toughne ss resisting
O P_2006ROII6Il
FRACTURE AND GAS DECOMPRESSION VELOCITY Stress (pressure }
Initial pressure {stress
arrest stress level
-fracture velocity
l---
- -- -
- --gas decompression velocity
1. Steady state fractu re propa gati(H'l occurs »hen t ~ e t'M>CU Neo interw<; l . 2. T he limiting conditi(H'lis »hen the two CUNeS beco me la ngentiol , in",e.se the t(MJghn""s and the fract ure will arr""t.
Veloc ity
23
FRACTURE AND GAS DECOMPRESSION VELOCITY
fracture velocity
Sire>, (pressure)
gas decompression velocity
Arre st ...... lead state fract ure ro atk! \
ropag a/e
Velocity
GAS DECOMPRESSION VELOCITY •
Each decompression wa ve travels at a particular velocity.
•
The deco mp ression characte ristics of the product are, primarily, dependent
on:
DECOM PRESSION :
• internal pressure • temperature • gas composition •
T he lower the is the percentage m ethane (compared to the higher hydro carb ons), the high er the initial pre ssure, or the lower the temperature , the 'slower' is the overall decom press ion wa ve .
Pressure Tempera ture Gas composition
2·
FRACTURE VELOCITY •
•
•
•
0_
The fra cl ure velocity is dependent on: VELOC ITY: • internal pressure • toughness • mate rial flow stress • diameter Pre ssure • wall thicknes s Toughn ess • backfi ll The larger the diameter, or the t hinner Flow stress the wall thickness , the higher the stress . Diameter and hence the the crack will propagate faster for the same toughness, Wall thickn ess Backfi ll is imp ortant. the fract ure velocity is Backfill highe r (compared to soil ) if there is no backfi ll and slower if there is frozen ba ck fill. The fracture velocity is obta ined from an empirical equation (containing the above param eters) limited to the full sca le tests it was based on .
2005 _ '
"
OTHER PARAMETERS THAT EFFECT DUCTILE PROPAGATION
25
THE EFFECT OF BACKFILL Batte lle 2 Cu rves Appr oac h
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o
_
No backfi ll
_
S ea bac k fill
_
De c om pre s s ure gas c urve
.
I
I
25 0
300
350
400
Deco mpression spe ed (m/s) © Po"spa n 2006 Rov6il
THE EFFECT OF RICH' GAS • •
Gases 'rich ' in higher hyd rocarbons (ethane , etc.} are ca lled 'ric h' gases Fracture control fo r pipe lines carrying rich gas mixtures often requires sig nificant ly higher toughness pipe compared to gas pipelines carrying nea rly pure methan e •
•
Methane+Ethane+etc
Rich Gas
this trend has been confirmed by severa l full scale burst tests.
W hy? • The decompression beh aviour of natu ral gas can be approximated by ideal gas behaviou r. • However, the decompression characteristics of rich gas are mo re compl icated .
x
• Rich gas es cannol be descr ibed by ideal gas assum ptions. • A$ ME 83 1.8 requires additiona l toug hness conside rations for rich gases
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26
THE EFFECT OF RICH GAS •
Rich gas can: • 1. decompress more slowly initially (compared to natural gas) • 2 . additionally, a liqu id ph ase (a two ph ase regio n) can occur at high pressures. leading to even slower decompression ra tes . • Two ph ase behaviour causes a discontinuity in the decompression curve • The effect of these slower decompression speeds is more driving force at the crack lip • Therefore a higher toughness requirement
•
The Battelle Two Curve Model can be used to estimate the arrest I propagation conditions for a pipeline conveying rich gas . • Ar1 -ad hoc" decompression curve for the gas mixture of interest is req uired . ca lculated using a dedicated gas decompre ssion model • The model needs to be validated for the relevant gas cc mpo smon. temperature and pressure .
c_ ~_,
THE EFFECT OF RICH GAS
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27
THE EFFECT ON OFFSHORE PIPELINES •
Full scale tests by Battelle and CSM have shown that water acts in a sim ilar way to bac kfill; the deeper the water, the mo re benefic ial effect.
•
Hence, would expect offshore lines to have lower toughness requir ements for ens uring arrest.
•
The Battelle Two Curve Model accommodates backfill effects, including water, ,. 0 . 12 0 through empirical corrections (but note 10 0 that thickness of offshore pipelines may lie outside range r-of applicability of the TCM) ,
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FRACTURE LENGTH
28
FRACTURE LENGTH •
Britt le fractu res result in (large) pipe fragments being th rown some distance from the crater; these are a hazard
•
Ducti le fractu res norma lly run along the top of the pipe, and the pipe remains in the crater. If the min imum ductile to ughness requirement is satisfied by all pipe in a pipeline , then the fracture length should be between two and three pipe lengths,
• •
If the minimum ductile toughness requirement is not satisfied by all pipe in a pipe line . then: • If most of the pipe is 'arrest' pipe . then the re is a high likelihood of a fracture length of a few pipe lengths . • If mos t of the pipe is not 'arrest 'pipe, then there is a high likelihood of a fracture length of many pipe lengths.
•
The likely length of a fracture can be estimated using simp le stat istical methods if it is assumed that the 'arrest' pipe (acceptable toughness) is randomly distributed, and the proportion of 'arrest' and 'propagate' pipes is known (or estimated),
CRACK ARRESTORS FOR DUCTILE FRACTURES
'" P o, ,,,,," 2006 Rov61 '
29
CRACK ARRESTORS FOR DUCTILE FRACTURES •
•
Brittle fractures are very fast and show littl e pipe wall deformation. •
crack arrestors of little value
•
we must prevent a brittle fracture propagation!
Ductile fractures are slow , typically 100 to 300 rns-' . and are characterised by: •
the fract ured pipe beh ind the running crac k to bulging outwar ds, creating high longitu dinal stress at the crack tip , and
•
ovansauon ahead of the crac k tip and an elevated hoop stres s.
CRACK ARRESTORS FOR DUCTILE FRACTURES •
The basic arrestor concep ts are (for a ductile fract ure): t . Re strict flap open ing (e.9 wrap the pipe with wire). 2. Redu ce the hoop stress ahead of the crack (e·9 by inserting hea vier wi. :1 pipe ), 3. Chang e the direction of the crac k (e.q . by inserting a brittle g irth weld). 4. Add mass to the pipe wall .
•
In most applications, arrestors based on eit her 1 or 2 are used .
•
Note that the new higher grad e stee ls may requ ire stronger/longer crac k arrestors than lower grade steels
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30
CRACK ARRESTORS FOR DUCTILE FRACTURES •
When choosing an arreste r, consider: • Type of arrester; • l engt h, thickness and material of arrestor; • Stren gth and stiffn ess; • Corrosion control of any steel attachm ents; • Spacing and location of arrest ors,
•
Ther e are a number of examp les of crack arrest ors fitted to pipelines in the USA lines, These include : • Loose steel sleeves filled with epoxy to prevent mo isture entry; • Steel sleeve crack and buckle arresters: • Clock spring composi te fibre wraps.
at
CODE GUIDELINES FOR CRACK ARREST
"
31
FAILURE BEHAVIOUR OF PIPELINE DEFECTS s. • ~ ""'".. "'"'"'".. Part -Wall Defect
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ASME B31.8 REQUIREMENTS FOR FRACTURE PROPAGATION CONTROL: Brittle Fracture •
ASME 831.8 refers to API 5L, supplementary requ iremen ts SR5 or SR6 . • For o wn specimens, ASME 831.8 and SR6 require that at least 80% of the pipeline batches (tieats') sha ll exhib it a fractu re appearance with a shear area of 40% or more.
• Th is specification is based upon two samples taken from one pipe in each heat • II is based on non-published data collected by API, and co rresponds to an ave rage of all of the heats of appro ximate ly 75% shea r area • If the test tempera ture corres ponds to the minimum ope rating temperatu re, t hen th is specifi catio n wi ll assu re t hat appro ximately half of the line pipe supplied will fai l in a d uctile manner (i.e. approximately half of the pipe will have a FPn abo ve the minimum operating temperature) .
AP I 5L requires a DWTT shear area of 2::40%
32
ASME 831.8 REQUIREMENTS FOR FRACTURE PROPAGATION CONTROL: Ductile Fracture •
ASME 831.8 refers to the supplementary requirements of API 5L. • For example, the (average) line pipe shear area of the Charpy specimen
must be ~80% • The all-heat average Charpy toughness should exceed a value calculated using one of four quoted predictive models:
AP I 5L requires a Cha rpy shear area of '2:80% + a toughness calculated from models
• Battelle, the American Iron and Steel Institute (AISI ), British Gas , and British Steel. E.g .:
Battelle. . AIS!. .
Full size C,= O.0108"h2R'l3t1l3 Full size c, = O.0345crh3/2D1I2
THE EPRG RECOMMENDATIONS FOR CRACK ARREST TOUGHNESS •
The EPRG recommendations give toughness requirements for a range of line pipe stee l grades and diameters.
•
The recommendations refer to full size Charpy specimens, and the specified values are based on an average of three values.
•
The recommendations assume ductile behaviour, i.e. at the minimum design temperature the requirement for an 85% shear fracture area test (to API RP 5L3) will be satisfied. determined in a
own
•
The recommendations do not apply to rich gases, or to pipelines with no backfill or frozen backfill
•
T he recommendations are bas ed on buried pipelines in the Western world , operating at ambient (e.g. 5 C) temperature.
RE G , PISTONo,V , VOGT,G., D E MO FO~T',G , and ;0"£ 5 ,0 G.. EPRG fl<,rom"",nd.'"" I", C'ad< Am'" r""!l N ", ,, l"Ogosr,..,,,," C"'" Pope J R "rem. t'",,.,.v'" 34 J"'Il"'g . _ Oc t o ""'_ ~"".,""" , ,.,,, , pp. 6Or-<;, 1
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33
THE EPRG RECOMMENDATIONS FOR CRACK ARREST TOUGHNESS • • •
•
•
The EPRG recom mendations do not clea rly indica te the appropriate test temperature . The DWTT shear area requirement at the min imum des ign temperatu re ensures that the ste el is on the upper shelf. The FPTT determined usi ng DW TT specimens will be higher than that specim ens are full determined using Charpy test spe cimens (the thickness specimens). T herefore the temperature of the Charpy test can usually be at room temperature, because the steel is on the upper shelf and the upper shelf impa ct energy is not temperature dependent unless the stee l shows an increase in the <, upper shelf with temperature • . ~
own
;-<':
(a 'rising shelf steel). However. it is good practice to conduct
,
rising shelf
Charpy tests over a range of temperatures, inclu ding the minimum design temperature.
C_2006_'
"
THE EPRG RECOMMENDATIONS FOR CRACK ARREST TOUGHNESS c harcv v-octcf (fu ll-size) for gas lransmission pipel ines operating aI 62.5% SMYS Pi e outside diametor 00 mm ~51O ~610 ~720 ~ 1 020 ~1 1 20 ~.8_29 Gr",I" _+ ; 920 $820 <920 ~ 51 0 -·6 10 crzo <' 020 ~'12 ~ ' 22 L240 xas
~ X(~+p,OO X52 ~ XOOl
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L480 X7QL. L550 XSOl
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Cha rpy V-f1otdl (full-size) for gas trans mIssion pipel ines oper ating at 12% SMYS
G._ ¥-w1f~?5 L290 X. 2 L360 ..1~
L.'SlXOO L«5 X65 L480 :00 L550 X80
00 mm .,,,,diame1er -sec >720 " ~" 2'0 -S,O ' -610 ."" ."" "'" S102'O., <, 12'0 ,,, ., ., ., " ., " so ss " "so ssse " "" '"" " " " " (lUIIoidot
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34
BASIS OF EPRG RECOMMENDATIONS Gra de
Basi s of EPRG Tou gh ness Recommendati on s
X80
1.0
X70 and X75
0.90 xAISI
Below X7Q
0.75 xAISI (minimum fu ll size Charpy of 40J)
x Battelle
BASIS OF EPRG RECOMMENDATIONS •
The EPRG recommendations do not give the lower bound toughness required to arrest a ductile propagating frac ture in all of the pipe purchased 10their specification.
•
The recommended minimum toughness of 0.75 x AISI prediction for arrest takes into account the statistical distribution of Charpy toughness within a pipe supply. This requirement ensures that half of the Jinepipe supplied will meet the predicted arrest requirements (i.e. the AIS I predicted toughness), based on a statistical analys is of the measured Charpyenergy.
•
The recommendations are based on statistical analysis of actual Charpy energies, showing that approximately half of the supplied pipes will have a Charpy energy in excess of 1.3 times the minimum specified value .
35
DNV OFFSHORE STANDARD OS-F 101 REQUIREMENTS FOR FRACTURE PROPAGATION CONTROL <-30mm
Wall Thickness
Out side diam eter (mm)
<=610
1<=820
1<=11 20
Ch arpy To u gh n es s (J)
SMYS
245
40
40
40
290
40
43
52
360
50
61
75
415
64
77
95
450
73
89
109
485
82
100
124
555
103
126
155
Cak:ula1loll:i to otllaI n Cv
lISe
-Fracture arrest properties for larger wall thicknesses and diameters shall be subject 10 agreement . ' Charpy V rl()(ch (full scale) ' Joules: Transverse values: Average value of three specimens) ·Minimum Individual results to exceeo 75% of these values.
EPRG G
FRACTURE CONTROL PLANS
C_2OOI_'
n
36
FITTINGS
FITTINGS .Pipeline fittings include forged bends, tees , and flanges.
_ They are usua lly short and thick, and occur at relatively infrequent intervals along the pipeline length . _ It can be assumed that a fracture in a fitting propagates only as far as the tough pipe to which it is welded: GAS _ The refore , fracture propagation is not conside red a
problem and the frac ture arrest philosophy that is appl ied to line pipe is not appropriate. _Conseque ntly, fittings are designed to protect aga inst the less severe case of fracture 'initiation'.
37
FRACTURE CONTROL PLANS _ We usually include our ar rest toughness requiremen ts for our gas pipeline in a 'fract ure control plan' _ Fracture control is concerned with controlling fracture initiat ion and propagat ion e a ecause higher toug hness levels are required to arrest propagating fractur es than are required to avoid initiation of fracture, the specification of sufficient toughness 10control fast fracture will ensure the line pipe is sufficiently tough 10 give ductile initiation that is controlled by yield (flow) stress rather than toughness' . a conseqoenuy the fracture ptan 1$ usually focussed on lim Iting fracture propag ation a r neretore it will specify two toughness measures 10 limil brittle fractures and ductile (sometimes called tearing) fractures in the line pipe body . · Propagating Mille or ductile fractures in longitudinal welds" (SAW and ERW ) have not been recorded in operating pipelines. • Conse quently, the fracture con trol plan does not have to include longi tud inal welds or heal affected zones . C'''''''- 2000l Ro>t\o" 'AS 28M'
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PROPAGATING BUCKLE
38
PIPELINE BUCKLING IN BENDING
•
When we bend a pipe we can increase its curvature . The bending eve ntually becomes unstable and we cause wrinkles on the com pressio n side, then a buc kle forms . • The curvature is no longer uniform and it loc alise s at the buc kle. to give a 'kink'
Wrinkles (magnified)
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C_2006_'
-n
PIPELINE BUCKLING •
A large extern al pressure can also cause a pip eline to ovalise and co llapse . but the bu cklo is no longer a local wrinkle on the co mpression side, bu t it spre ads out and can move alo ng the pipel ine in a dumbb ell ('dog bone') shape . • Collapse occurs when exte rna l hydrostat ic pressure causes a pipe to beco me unstable and buc kle locall y. • Collapse resu lts in gross plastic deform ation of the pipe cross-section . • It is a Iorm of loca l buckling .
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• Tensile axial loads, or bending loads, reduce the collapse pressure' . •_
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39
PIPELINE BUCKLING: Example Equations' _External pressure on a pipelin e can lead to yield ing or collapse of a pipelin e . Suckling of a long (leng th >1 .110(0/1)0.5) pipeline, buc kling primarily depends on its 011 ratio (oute r diameter/wall thickness), in the same way as a col umn in pure com pressio n depends on its slenderness ratio. _For large Olt ratio s, buckling occu rs while the mat erial is still elastic (elastic buckling ). The external pressu re (Pe. psi) to cause this buckle is:
. Pe ::: (2E1(1-u2 )).(VD)3, wh ich gives a hoop strain> [1/(1-2u)).(tlD)l . wt1 ere E is Young"s mod ulus (psi), aro u is Pois sooratio . for a Poisson ratio of 0.3 (steel), P, " 2.2E{VD)3, .....t lich giv es a hoop strain" 1.1(U0 )2
_For short lengths of pipe, the stress in the pipe wan may reach the elas tic limit before buckling occur s: . Plastic limit to- short pipe s, P p _where
OJ
'"
20 jUO
is material yield strength (psi)
. For interm ediate lengths of pipe . see reference at bollom of page for buckling pressure O~.....- 2006_6."
PIPELINE BUCKLING: Example Equations' _At small Olt ratios, buckling results from yielding of the cross section . This yield ing occu rs at an external pressure (P) :
o P, =
2.(tld).cry
_where 0 , is minimum yield strength (psi) in hoop directi on
_At intermediate valu es of 0 11. the collapse pre ssure . Pc. is: . p c = (P ! ' P e "l(P ' r2 -+ P e 2)0.' _ASM E II and ASME V lIl give cha rts for the design of piping subjected to extern al pressures
0_
........ _ '
40
PROPAGATING BUCKLE SUBSEA _ A pipeline under external pre ssure, or high bendi ng loads can also support a 'propagating buckle'. _T his is a buckle that con tinues to propagate along a pipeline , and may occur in offshore pipelines under high layi ng loads.
C_2QllO;_.
"
PROPAGATING BUCKLE: Cause e'Two things m ust ex ist for a propagating buckl e: _A buckl e m ust exist before the propagation occu rs. e'Ihe exte rnal pressurell oad must be above a 'pro pagation pressure', P PI' _The buckle will continue to propagate until the external pre ssure dec reases to below the p ..... or it meets a physical obstacle, 8 ·9 · a buckle arrestor. _The Ppi will be lower than the pressure to buckle the pipeline A 'wet" buck le is one that fails the pipe . and allows water ingress . A 'dry' buckle is whe n the pipe is not broken
ez
41
PROPAGATING BUCKLE: Calculation . Offshore design codes (e.g. DNV OS F101) give guidance: . Propagation pressure =Ppr=3S(lyIl(tl D)2-5 _1=wa1l thlCkress, 0 " pope d iamet er. Oyi$ the YIeld s1fength. a is a factor rangIng from 085 10 10. a r'ld depends on type 01 line pipe used.
_See ONV ooeume nl!of lull detai ls and umts.
PROPAGATING BUCKLE: Buckle Arrestors Pipe wall coll ap se du e 10 external pressure
Buckle w ill propagate
---- ---- ----._,42
ADDITIONAL INFORMATION
THE TITANIC The Roya l f-1ail Ship Titanic: Did J "'!f:1al1U'1'ic.a1 Failun Ca uve J~ght eo Rernember t
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Did the Titanic sink be cause
of poor toughness?
43
THE TITANIC
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a rnese are Charpy tests from the actual Titanic hull. _ Compare the Titanic hull steel with a modem (A36) steel. _ Clearty. the steel used for the hull was not suited for service at low temperatures . _ The seawate r temperat ure at the lim e of the col lision was -2"G. 0 _ _ 2 ' D _"
THE TITANIC _ The stee l used in RMS Titan ic was probably the best steel availa ble in the period of 1909 10 1911, _ but it wou ld not be acceptable at the present l ime for any construction purposes and particularly not for ship cons truc tion ,
_ Would a ship constructed of modem steel suffe red as much dam age as the Titanic in a similar accident? _ If the Titanic had not collided with the iceberg, it could have had a long career _ Its sister ship - the Olympic - had a career of ove r 20 years _ II was built of similar sleel , in Ihe same shipyard, and from the same des ign
_ T he o nly difference was a big ceberq.. ..
44
Utility Pig and Intelligent (Smart) Pig Inspection
Penspen Integrity
Lecture note - intelligent pigging tec hnology is alwa ys changing and improving. Therefore . some 01the gu idelines, tolerances , accuracie s, etc.• quoted in this lect ure may be 'out o f da le '. Ch eck with pig su p~ iers fo r latest information n .....'
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1
PIPELINE INTEGRITY? .Pipeline integrity is ensuring a pipel ine is safe and secure. It invo lves all aspects of a pipelin e's des ign, inspection , management and maintenance. e 'Ffus presents an operator with a complex
,.,
Audit IIasellne
Assessment
_
'j ig saw ' to solve if they are to maintain high integ rity . Pipeline integrity management is the managem ent of all the elements of this complex jigsaw _ The management brings all these pieces of the jig saw toge ther.
a
INSPECTION OF PIPELINES • The industry is now moving to 4 cat egories of inspecting ('assessing') our pipe lines: • In line inspection, using intelligent (smart) pigs • Hydrotesting • 'Direct Assessment' • This is can be a mixt ure of methods. • For example, we can do above ground surveys of ons hore buried lines that can detect problems with the corros ion protection and pipeline coatings . l.e inspecting for external corro sion. • These are 'indi rect' measu rements. • W e can excavate the pipeline and measure wall thickness loss, • This is a 'direct' measurement. • Combin e indirect and direct , and you have direct assessment.
• 'Other' technologies - this allows new & future techn ologies C~2l106_'
3
PIGS: WHAT ARE 'PIGS'? •
'Pigs' are devices that are inserted into pipelines and travel along the pipeline with the product flow .
•
T hey can travel up to 1000km , but typi cally travel 50km (a typi cal pip elin e 'section' )
-.,._ ... ..... ~
Assorted plastic cups or discs on board the pig allow sealing, guiding, spacing, scaping, etc..
•
2
PIGS: WHAT ARE PIGS? 'UTILITY PIGS: The se are tool s that help clean , seal, and ma inta in our pipeline
'INTELLIGENT' PIGS : These are tools that co llect informa tion on the condition of our i eline
Usually propelled by pipeline fluid 5
PIGS: USES INSPECTION
CI-E
DETECT CORROSlON. AH;l OTHERDEfECTS, ~ ""'COO'<
- '"
lINECOVER J,K) SJ'AANNG _~J>K)
~
REPNIt
1!'HIlITORS. PRE-
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Pigs help operation and effiCiency by : ·re moving subs tances and de bris that ma y hinder proces s systems or form corrosion ce lls -help detect defec ts ' providing an alte rnative 10 the hydrole sl
r
s
3
PIGS: The History... Cleaning pigs....
• 1870: the flow in a Pennsylvanian crude oil line decreased , due to paraffin deposits, and the pressure had to be increased. • To remove the deposits, a bundle of rags tied in a ball was pumped through the line.
____
t
• This first pig was upgraded to a bundle of leather • Leather swells when wet & creates a good seal for the bundle
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PIGS: The History... 'Condition' pigs.... • 1904: 4" line in Montana was covered by a rock slide during construction.
• A rubber ball was pumped through the line to detect damage.
...
"
. If the ball exited, undamaged, the line was not damaged . • Rubber balls have been used ever since for this purpose.
•
4
_ _ _ _ .a WHY DO WE CALL THESE TOOLS 'PIG'? • The origin of the name 'pig' is debatable.
• Early pigs were made of pipe or mandrel bodies, with flanges welded onto each end and rubber or leather cups • Early pipeliners used to comment about "hearing that pig squeal" as it passed by',
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UTILITY PIGS: Cleaning and Maintenance
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THE USES OF UTILITY PIGS: Foam Pigs _ Foam pigs are 'bullet' shaped , and are the most basic of our utility pig s.
• They are cheap cleaning devices. _T hey are lightweight and easy to work with and able to negotiate a variety of pipe (diffe ring diameters) and bend configurations (tight radius, mitre bend s) . They have a variety of densities of foam (very soft to very har d) . They can be 'bare ' (e.g. for drying a line ) or contain metal or plastic bristles (for cleaning/sweeping a line) . They are used for drying, cleaning , batching. product rem oval operations , etc .. _ They are regularly used fo r air removal prior to a hydro static test, an d drying after the test.
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6
THE USES OF UTILITY PIGS: Spherical Pigs •
Spherical pigs are usually polyurethane globes. filled or inflated with liquid (us ually glycol or lightweight oil).
•
They can ne go tiate very tight radius bends, and ar e us ed for :
• Sometimes we have solid spheres
• heavy-du ty service in the removal of liquid hydrocarbons and water from pipelines;
r--=:::::-
-is Pheres
• bat ching ; • hydrostati c testing; • Etc ..
Sphere pigs should never be run ,n ~n es tha I do not have s.pe<:ial now tees ,nstalled
ta
THE USES OF UTILITY PIGS: Mandrel Pigs . 'Mandrel' pigs have a central body lub e, cr 'ma ndrel', and various compone nts can be assem bled onto the mandrel. a T his allo ws ma nd rel pigs to be us ed for a sp ec ific duty, such as:
a batching; a gauging:
Mandrel Pigs
. sealing; cleaning/brushing;
a etc. a T he sealing discs . cu ps , bristles. etc., can be replaceable
C" - 2OOlI _
'
7
THE USES OF UTILITY PIGS: Mandrel Pigs _ Mandrel pigs can use either a 'cup' or a 'disc' as the sealing elem ent. _ These elements are des igned to allow the pressure of the line to seat the outer seal ing surface of the cup or di sc aga ins t the internal pipe surface . to ensure positive seal.
e c uos and discs are flexible, that allow them to adapt to out- of-roundness or varying internal pipe diameters.
Cups Discs
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THE USES OF UTILITY PIGS: Solid Cast Pigs _ Solid_cast pigs are moulded in one piece, usually from polyurethane, and are a general purpose pig for batching, displacement and routine pigging operations. _ They are easy 10handle and have excellent sealing capabilities. _ W ith the add ition of brushes. they can also be used for cleaning appli cations .
Solid Cast Pigs
e v anous configurations are available. including:
. spherical; . cup.-type ; and e orsc-tvpe .
te
THE USES OF UTILITY PIGS: Bi-directional Pigs a'Cup' pigs are unidirectional : Cup p ig s for u ni directi on al
operation. _Bi-directional pigs have discs placed at opposite ends of the pig, allowing them to be moved in either direc tion . • They can be used in the same way as 'cup' pigs; in particular, during hydrostatic testing (for air or water remova l), or can be filted with: _Brushes, for cleaning; ealumtnlum or stee l gauge plates, for gauging; atracker devices , for tracking ;
_etc..
Disc pi gs f or b i-d irect iona l ope rat ion.
THE USES OF UTILITY PIGS: Gel Pig _A 'gel' pig is a semi-solid chemical substance injected or placed inside a pipeline usually to clean the inner walls of powder-like debris such as iron sulphides and rust. _These highly viscous pigs are sometimes called 'qelly' pigs , _The gels can be water-based, or use a range of chemicals, solvents, and even acids. _Gel pigs are also used extensively to: remove water from pipelines; debris pick-up; batching; inhibitor/biocide laydown; condensate removal from gas lines; removal of stuck pigs; line filling/hydrotesting; etc .. Drive
Gel 'pig train '
Fluid
Separator
Debris
Ge'
Ge'
Debris Gel
linefill I
Debris Separator Gel Gel
9
THE USES OF UTILITY PIGS: Batching Pigs _ Satching pigs are used for batching or displace ment processes, and also for light cleaning. _ More cups or discs can be added to the pig where interfaces or contamination are critical.
56" batching
p;g
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EXAMPLE OF BATCHING PIGS
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10
EXAMPLE OF BRUSH CLEANING PIG
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EXAMPLES OF CLEANING PIGS/RUNS
__ 200II_'
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II
THE USES OF UTILITY PIGS: Cleanliness is important! _I n the earl y days (40 years ago ) the majo r reason for cleaning was inc reased flow throughput. _ Even small irregul arities insid e the pipe can cause turbulence in the product flow. Turbulence increases fr icti on loss. re duces capacity and puts
an unnecessary load on the pumps and compresso rs.
THE USES OF UTILITY PIGS: Cleanliness is important! _ Now, pipelines are cleaned to: im prove throughput; reduce operating cos ts; contro l corrosion; re move obstructions; prepar e a line for intern al
inspectio n, etc.. e lnternat cleaning can remove liquids and sol ids that can promote corro sion; _ ror example. bacteria can thrive under scale and sludge.
_ Many pipelines are injected with chemicals to prevents nfubit corrosion , particularly when there is bacterial co rro sion present a aut. if the chemicals cannot modify the environment supporting the corrosion (e.q. if the bacteria is under a srudge) they will not be effective, as most
chemicals have to contact what they are trying to control, so cleaning becomes essential _ The same cleaning requirement holds for a film ing inhib ito r that has to be depos ited on a surface of the pipe to form a barr ier between the pi pe steel and the environment.
12
WHEN IS A PIPELINE CLEAN?' _ Methods for determinin g if a pipeline is 'clean ' include: _ The clea nliness of the cleaning pig _ The amou nt of deb ris colle cted in the filler or stra iner s foll owing a pig run _ The reduction of operating pre ssure _ The increase in flow rate ef m oroveo product qua lity _ A reduction in the consum ption of com pressor or pump fuel _ A successful corro sion inspe ction _ The redu ction in corrosion rates of corrosion coupons
25
BENEFITS OF 'CLEAN" _ A major gas pipeline operator has stated his com pany spent $800,000 cleaning a single 3D-inch pipeline. _ The flow efficiency was increased from 58 to 96 percent.
_Th is company saved $1.2 million in compressor fue ls for the next seven months. • In anot her examp le, the project costs tota lled S640,000 . Of this, 5100 ,000 in capita l was spent on pig launchers and rece iver s, and 5540 ,000 spent for the cleaning operation . _ A total of 344 ,000 Ibs. (156 ,364 kg .) of solid s were removed in 12 batch runs. _ The pipeline efficie ncy w as increased from 71 to 80 perce nt. _ The sav ings were 5377,000 in com pressor fue ls during the first eight m onths . l DW .......... _ f -.....,, 2OOJ
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26
13
PIGS: Putting Then Into Pipelines
PIGS: Putting Then Into Pipelines
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PIGS - Putting Then Into Pipelines • Pigs are
inserted into a pipeline using 'pig traps', that are fitted with doors ('closures ').
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• They enter in a 'launcher',
• They leave in a 'receiver',
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I 29
INTELLIGENT (SMART) PIGS
15
FROM UTILITY PIGS TO INTELLIGENT PIGS • Early, pigs were all utility pigs , and had steel bod ies and rubb er, leather or urethane cups or discs . • They were des igned to 'plough', so they ______ were equipped with wire brushes. scrapers, etc ..
• In the late 1960s, the intellige nt pigs were develope d.
Intelligent pigs are designed 10 trave l up to 600 miles ( 1,000 km) in a single pass . but average pipel ine sectio ns are around 30 miles (50 km ) long.
C_
2006 _ ,
"
FROM UTILITY PIGS TO INTELLIGENT PIGS •
W e can have : • 'free flowing' pigs • these are propell ed by the fluid , and are tot ally self con tained (on board pow er, data col lection, etc.). • They do not interfere with flow
• Self co ntained pigs thai are pumped _____ through a pipeline • These pigs require flow 10 be regulated , ____ or a different fluid to be used
• tet hered (or cabl e) pigs . that are connected to a powe r supply or data acq uisition bo x via a ca ble . • These pigs can eithe r be driven by mo tors. or pumped thro 'lines. and are used for ·unpigga ble' lines such as loading lines.
16
INTELLIGENT (SMART) PIGS - Many Types GEOMETRY MEAS UREMEN T
METAl LOSS DETECTION
LEAK DETECTION
PIPELI NE PROFILE
TE MPE RATURE AN D PRESSURE RECORDI NG
MAPf' ING
BEN D MEASUREMENT
CU RVATU RE MON ITOR ING
PRODUCT SAMPliNG
PHOT OGRA PHIC INS PECTION
W AX DEPOS IT MEASUR EM ENT
CRACK DETECT ION
MOST COMMON TYP ES OF PIG AR E GEOMETRY AND METAL LOSS
INTELLIGENT (SMART) PIG - Position Along the Pipeline e'ooometer' wheels measure where the pig is in the pipeline.
_ An 'odometer' is any device for measuring distance
17
INTELLIGENT (SMART) PIGS - Detecting
'Features'
35
INTELLIGENT (SMART) PIG - Specifications T
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WHAT MAKES A PIPELINE UNPIGGABLE'? •
Our older pipelines were built before intelligent pigs were developed
•
Before intelligent pigs , internal access to/through a gas pipeline was not a requirement, although liquid lines needed some access - e.g. for cleaning. So, ma ny pipelines are not piggable. Reasons: • No pig traps
•
• • • • •
Bend radius <1.50 Mitre Join ts > 10° Unbarred branch connecto rs Reduced -bore valves Diameter changes> 2"
• Low pressures or flows • Mani folds • Etc .
•
Main problem in USA is unpiggable valves and unpigga ble bends
ALWAYS CHECK WITH THE PIG SUPPLIER
C_2006_,
Q -• Perfectly ---,----straigh -t, ---= from end to end. THE IDEAL PIPELINE FOR A SMART PIG••.?
•
Constant internal diam eter, and no weld pene tration .
• •
Perfectly round . Polished or epoxy coat ed inside surface,
• • •
No off -takes. No valves or other devices. Pumping light , unrefined oil at a speed of about 1 mJsec.
•
Therefore, unfortunately, not every pipeline can be inspected with a smart pig . Always check with the pig provider, to see if your pipeline can be pigged .
•
19
INTELLIGENT (SMART) PIGS REQUIRE A VERY CLEAN PIPELINE •
If you are going to intell igent (smart) pig a pipe line it MUST be very clean .
•
'Standard' cleaning pigs may not be suffici en t to clean a pipeline pr ior to intelligent (smart) piggi ng .
•
Thi s is because smart pigs such as MF L pigs have powerfu l brushe s/mag nets that re move residual wax , etc., left beh ind by the clea ning tools. The se res idue can foul or destroy sen sors.
•
Pigs using ultrasonic technology have problems as residual substances such as wax can attenuate their signals.
•
Theref ore , pre- pigg ing cleaning is often a special progr amme (e.g it m ay requ ire a mag netic cleaning pig 10 remove fer rou s deb ris) normally ca rried ou t by the sm art pigging company itsel f. 39
INTELLIGENT (SMART) PIGS REQUIRE A VERY CLEAN PIPELINE
20
CLEANED FROM THE PIPELINE
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CLEANED FROM THE PIPELINE
Sa nd ,e""'_a d from pipeline
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21
I
INTELLIGENT (SMART) PIG - Tolerances (Guide Only) •
Internal Diameter - Standard pipeli ne toler ances, but variable diameter pigs are being developed . • Most larger diameter pigs can dea l with diame ter change s of 2-4" • Variable diam eter toots are bei ng developed (e g 24 /36", and 28 /42" )
•
Bends - Most pigs can negotiate 1.50 under certain conditions. • Mitre bends - atout tzv in angle (but check) Forged Ben ds - it's best to ha ve the additional material on the outer diameter.
•
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• •
Bend Ovahty - 2% or less Low pressures - below about 10bar (145psi) it is not po ssible to drive a conv entional pig withou t dangerous speed excursions
•
Off-takes- Intell igent pigs can negot iate 60% . Utility pigs can safel y trave rse 70% (of nom inal size) out lets. It's good practice to install guide bars for greater th an 50%. Valves - Full bore , but some pigs can negotiate some reduced valv es .
•
....
But always check with the pig supplier.
INTELLIGENT (SMART) PIG - Operational Restraints: 'Rules of Thumb'
• •
Most intellig ent (smart) pigs have speeds within 1 to 10 mph (1 to 5m fsec) : • 1-2m/sec for UT tools. • 3-5m/sec for MFL • New pigs have speed control (this can reduce operational costs), Utility pigs are 2 - 10 mph in liqu id lines, and 5 - 15 mph in gas lines. Inertial mapping . with GPS will elimi nate above ground markers
•
Temperature :
•
•
Intelligenl pigs are limited by their electronics: upper limit will be about 80 C and increasing
•
Utllity pigs are limited by the polyurethane or elastomer seals: upper limit ecco t 60 C.
every year.
•
Pressure : •
•
•
Intelligen t pigs have instrumentation sealed in pressure tight containers which means pressure restrictions: limit is 1000 psi, but many will be > 2000 psi, Utility pigs usually have no pressure limits.
But alway s check with th e pig supplier.
22
TYPES OF INTELLIGENT (SMART) PIGS· Geometry
45
TYPES OF PIGS· Gauging _ GA UGING - We wi ll often use simple, cheap 'gauging' pigs to check the bore and profile of a pipeline. _These gauging pigs have special plates mounted on bo ard thai deform if the y collide with a rest riction . arhese gauging pigs will tell us of problems in the pipe bo re by emerging with the plates denied or damag ed. _H ow ever, t hey w ill not tell us wher e the damage is, the number, or its dimensions
23
TYPES OF PIGS· Gauging
TYPES OF PIGS - Geometry••• the principle _ A 'geo metry' pig is a 1001thai (usually) has arms (calipers) on board that deflect when they pass through, or in, a restriction
Cup slee ve _
a-
Odometer whul
Reeor ding unit
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Sensing whe
"
TYPES OF PIGS - Geometry... 'Caliper' _ Early geometry pigs were caliper too ls. _ They used mechanical sen sor s ('fingers'), and were aimed at finding 'restrictions' in new pipe line s . _The ea rly caliper pigs could detect 3 to 4 inch deep dents or buckles".
In the 19605. Ill e hmlted num ber of
<:ahP&f arms. mean t only large den ts could be detected. Sma ll or shallow dents could be missed
_T hese tools would not provide o'clock position _ Most of these defects we re in the lower half of the pipeline due 10poor ditch pa dding or failure to rem ove skids .
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One of the first cali per tools was TOW 's 'Kauper' pig
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TYPES OF PIGS - Geometry••• 'Caliper' _ API 1160 states that 'Ca lipe r' (as opposed to 'deform ation' tool s - see next) tools measure deviatio ns in the geometry of a pipeli ne 's diameter.
_ Changes in the pipe diameter geometry can be due to pipe bends, dents, buckles, gate or check valves, or changes in wall thickness. _ Today, Caliper tool can use me chani cal arms or electromagnet ic meth ods 10 sense the ovalil y of Ihe pipe .
a c euoer too ls are used to verify that pipel ines are capable of passing othe r tools such as corros ion lool s and 10inspect for buckle s or dents in the pipe . _ Buckles and dents can be the result of pipe settlement during or after construction. _ See AP I 1160 for more information
50
25
TYPES OF PIGS - Geometry/Deformation ••• current tools _ We now ha ve many 'geometry/deformation' tools on the market" _ The old caliper tools have been replaced by too ls that can locate (distance, o'clock) and rep ort dents of Q,25inch deep, and have a threshold of O.125inch. _ The old too ls had the ir sensors (calipers) inside the cups of the pig . Th e new toots have sensors out side the cu p - in contact with the pipel ine .
C_2006_'
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TYPES OF PIGS - Geometry/Deformation••• current
tools _ T he nam es of these tools has change d. _ We now ref er to 'deformation' tool s that ca n measure very sma ll changes in geometry, down to a.Ol inch. _ They are now high resolut ion with arms at - 1 inch spacing aro und the pig, compared 108 or 16 arms in total on the
older pigs . We now consider a 'caliper" tool as a tool used to meas ure the internal diameter of a pipeline A 'geometry' or 'deformation' tool is a tool that measures deformations in the pipe. See A PI 1163
__ Cli,'"
"_2008_'
26
TYPES OF PIGS - Geometry/Deformation ••• current tools _T hese tools can pass through large defor mations (e.q . 25% pipe diameter) _ They can operate at high press ures (2000 psi) and negotiate tight bends (1.50)
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TYPES OF PIGS - Geometry/Deformation••• accuracy' 16" pipeline. Inspected 2000-2003
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Predicted Dent Depth, % Diameter
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27
TYPES OF INTELLIGENT (SMART) PIGS· Mapping
_ Mapping tools are based on inertia l navigation, using built- in gyroscopes and accelerometers, and they can establish the geographical coordinates of the pipeline. _ The information includes the coordinates of girt h welds and is use ful for creating pipeline align me nt maps, populating GIS information syst ems, and determi ning pipeline ground mov ement. _ See API 1160 for further information
y
x Z Inertial naviga tion systems (INS )
ss
TYPES OF PIGS· Mapping _ Mapping pigs are base d on inert ial navigation using gyro scopes and accelerometers . Geopig, developed by BJ Pipeline Inspection Serv ices , was the first on the ma rket. _ II is a pipeline internal inspection too l that provides complete pipeline geometry data, including _ information on dents . buckles, wrinkles . ovality, bending strain and pipe centreline. _ It has an inertia l measurement unit similar 10the type used in fighter jets to monitor pig position and altitude, X, Y and Z coordinates (tpitch, yaw & roll'), etc..
Geo::II>g in_ geometry 1001. ~le _ caIopet "'...... T.... lormolltlfl Geopig ,eplaC8IDYOd10 be !eM eccu ,altt
_ Many piggi ng companies now offe r this type of pig.
28
TYPES OF INTELLIGENT (SMART) PIGSMeasuring Metal Loss or Wall Thickness
O_2OClli_1Io 1
TYPES OF PIGS: Metal LosslWall Thickness Smart Pig _ Smart pigs came on the mark et in the 19605 to detect & size m etal loss (corrosion)
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a'ruboscope & vetco. • Full circumferential 'MFL' in 1966
_ 1978 - 'high' resolut ion pigs developed by BG in UK _1 9805 - number of MFL vendors increased _ 1986 - pigs using ultrasonics arrives, 10 measure wall thickness _ 19905 - improved technology and new products come on market
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29
TYPES OF PIGS (METAL LOSS): 'MFL'
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TYPES OF PIGS (METAL LOSS): 'MFL' •
Magn eti c Flu x Leakaqe . The pipe wall is magnetised (saturised) by permanen t magnets. and any metal toss will cause magnetic fields to distort . A detector senses this distortion. • These pigs can run in either liquid or gas lines , and can measure losses even in thin walled pipe . • Gives a relative (i.e. percent wa ll thickness) measure of defect depth • The more sensors, the high er the 'resolution, giv ing bette r sizing of narrow defects
30
TYPES OF PIGS (METAL LOSS): Basic MFL layout •
All pigs have d iffer ing layout s, but they all require:
•
• A drive module • A module 10 carry the magnets and sensors • A modu le to carry reco rding/pr oces sing equ ipment • A module to carry powe r (batteries) • A module to carry odometers These modules can be combined , particularly on larger diameter pigs
Drive module
Magnets + sensors
Processing
Batteries
Odometer
at
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TYPES OF PIGS (METAL LOSS): MFL Illustration
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62
31
U
TYPES OF PIGS (METAL LOSS): Resolution of MFL Pigs •
Standard resolution • • • •
•
Old type of MF L pig Few (an alog) sensors: eve ry 40-150mm No 10 /0 0 discrimin ation Detection /sizing thre sho ld: - 20· 300f0wt
High resolu tion • • • •
•
More rece nt tecnooioq v More (digi tal) sens ors : every 1().17mm 10100 discriminatio n Detection/sizing threshold : - 10% wt
>30 %
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r
I
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I
•
[; 10%
Very high resolution • • • • •
New est techn ology More (digital) senso rs : every 4-8mm 10 /0 0 discrimination Det ection thres hold: - 10% wt Sizing can be +/-5%wt
>10% +/-5%
TYPES OF PIGS (METAL LOSS): MFL Sensor Technology •
IW Ire
~~
•
In til e 1990s. Ihe sensors on MFL pigs started to change • Originally, MFL pigs used 'induction coil' sensors' , These sensors mea sured the cha nge in mag netic fields • Now , 'Hall-e ffect' sensor s are used that ca n measure the ac tual (absolute) strength of the mag netic fields . • These sensors coll ect flux data in the axial, radial and circu mferential directions • Ha ll sensors can chec k to see if there is adequate mag netic fie ld satu ration (this is impo rtan t: poo r ma gnetisation affects data quality) • The use of Ha ll sensors allows more sensors 10 be fitted to the pig , and hence better resolution
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32
TYPES OF PIGS (METAL LOSS): MFL Fields'
(J
Magnetic field Magnetic field disturbed by defects with width , in this orientation. Flux leakage decreases with decreasing defec t depth and width Magnetic field not disturbed_ by defects with no width, in this orientation
,n
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Therefore, axial or narrow defects very difficult to size/find
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65
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TYPES OF PIGS (METAL LOSS): MFL Signals :Si t. v- ...
_ I,.... _ _ ........-
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33
TYPES OF PIGS (METAL LOSS): MFL Signals Width (note- Estimat ing defect width /
is not straightfo rward. This is beca use the signa l spreads in the circumferential direction , and the amount of spread depends on the defect length. dep th, and width .
-- .
Length " " I
.
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TYPES OF PIGS (METAL LOSS): MFL Signals (courtesy GE·PII)
Spiral weld
Corrosion
.
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TYPES OF PIGS (METAL LOSS): Accuracy & Reliability
_The accuracy and reliability of a pig is very important to us _Remember.. . we rarely assess a defect... we usually assess a defect report. _If the defect report, e.g. from a pig, is unreliable, your defect assessment is unreliable! ~
69
TYPES OF PIGS (METAL LOSS): Accuracy & Reliability
~~
j;~ 70
35
TYPES OF PIGS (METAL LOSS): Accuracy & Reliability
"
TYPES OF PIGS (METAL LOSS): MFL Accuracy'+/·10% t, 80% of the time... 7' % Co nfidence (% Data within t he standar d dev iati on s)
Num ber of Standard Deviations fr om Mean
0. 67
50
ee.a
1
80
1.28
90
1.65
95
1.96 95,4
98
.. ... .. ..
..
NORMA L DIS T RIBUTION
...1,
Da t a ~. 1 n
""
Bl an <1 .~d.
dev lilt ,on
!
.2
'"
.
.. " ."\•
,n
:n
lH
.l..- __
i
"I e
.
"
., ., , • , ., .•, " STM"DARO DEVI ATI ONS
2.33
~
~
.
2.58
99 99 .7 c: p........,
3
200II _'
36
TYPES OF PIGS (METAL LOSS): MFL Accuracy '+/.10 % t, 80% of the time•••?' Low Resolution (L R) Tool (ex amp le) Standard Dev iation
Sizing Tolerance
%
(%wall thicknes s, t)
(%wall thickness, t)
Confidence
15.6
+/-20
80
15.6
+1-10
48
15.6
+/-5
25
If this lR 1001 reports a 50% wall thickness defect, it wi ll be in the depth range 3.2% (50 % x (3 st . dey. x 15 6mm )) to 96.8% (50% x (3 st. de v. X 15.6»), 997 tim e in 1000· '
7.8
+1-10
If this HR tool reports a 50% wall thic kness % it will be in the defect. Confidence depth range 26 .6% and 99 73 .4% ,997 times in 1000 80
7.8
+1-5
48
Hig h Resolution (HR) Too l (example)
(%1)
Sizing Tolerance, ("lot)
7.8
+1-20
Standard Dev iation
"_
_
s ...
_
....-.. ._ _
------..-
_
_ ~
_
.... _
~
__
.
,
.
... _
"OI
~ '
~
~ ,
~
e-.
_ I P C I > 4 - -
TYPES OF PIGS (METAL LOSS): MFL Accuracy percent of wall
r::::-,---,------:-=::-,---_,---_'"i thickness _ Data from 19905 four pig vendors on 9 pipelines:
25%
+
a venoo- A..
previous detec tion le ve ls :tl0%
systema tically oversized depths by 1G-20%wt _ Vendor B ... acc urate on 2 pipelines (to +1.15%wt), but systematically undersized on another line (20-30%wt) e v erd or C .. . were accurate to +1· 15%wt in 4 pipelines
--
>tJ " _ . .. .. F_. _ '¥""I>W"II __ .........-_ _ . . - _..s-....
I '"~
10%
",+
~ ~'d.
I_I
~XHR detedlOfl levels :t5 %
-
, 1.0
_
20
30
Defect lengthtWa l Thickness
OoI»
l .... _
~_
~_
• £xI ....... ,' _
...."........""
37
TYPES OF PIGS (METAL LOSS): MFL Accuracy Raported depth ("tot]
_ Da ta from 19905 : _ MFL pigs do not detect "narrow'
"'"
de fects, due 10 limited number of sensors, • e,g, a wet gas pipeline failed from smooth internal corrosion ( 1.5m in leng th, 40m m 'Hide. 80 %wt in dep th , by C0 2 cor rosion _ The pipel ine had be en ins pec ted 3 months before the failur e with an MFL pig. with no dete cti on of these detects . a n eta ana lysis of de fects in the vicinity of girth welds is comp licated du e to the magnet ic nux lea kage sign als o f the weld intera ct ing with the de fect signals . _ Da ta opposite shows a pig oversizing defects in the vicinity o f girth we lds
s.. H J, M. Ja..-.. M \I
~
ec 60
•
" 20
•
//./
''''''''' •
,,-
Skll shaped
X
c
X
, °0
X
00
4(1 60 Adual depth (%11
80
. ' lr ~ pog ~ I "Il ~ 1of I\"I8laIIoA _
F_
"
Gr1h_~
/
0
20
"""""" '''''''''
"'" <;rado.
_ ' .S/MI .~
TYPES OF PIGS (METAL LOSS): MFL Accuracy ' • Corrosio n detects 00 e >ctemal wa ll
~ 100 , - - - - - - - - - - - -7-7--:" True accuracy
~
.~
~
~
80
~
_~
-e
[
~
" j
.g
60
40
•
20
o
20
40
Staled eccu racy . /-10%l 8O'lr. of the lime
60
80
100
Actual defect dep th from fiel d exc avation (%wa ll i hic kn ess, tl
It h as bee n not ed that MFL p igs over-es timate d eeper def ects, and un d er -est imat e sh all ower defects _ . _ -.a.
.....
38
TYPES OF PIGS (METAL LOSS): MFL Accuracy (cont.) • eorros.on defects on inlemal ....all
~
100
:to
80
~
, - - - -True-accuracy - - - - - - - --:7--:;>-'"
--
+/.18%1, 95% oI lt1e time
-e
su
'0
~ ~
60 40
1:1
~
I
Sta te d ac curacy
20
+1-10%1, 80% of the lim e
o
20
100
80
60
40
Actual defect depth fr om fiel d excavation (%wall thi ckness , t]
C_2OOII"*"6-'
__
~
. ....o>-..._
•
T1 O< .... O " ~ _ '~"""
TYPES OF PIGS (METAL LOSS): MFL Accuracy '
";•. so -e
!u
••a.
so 30
·
a
•o "
True il(cur acy : ~ 12'"
.! 10
WT 95 ". o f tIme
C•
O ~OL_~"L_C2CO----,"O---,-~..:--C'CO--60~---:l" Actua l ee reer dep th '.om in ·fIeld inspect ion. '!lo WT ° Me ' e l ro.... uused by COHO.'O" .
C"- 2006_'
00fW_"'_ _ ."....,'9
• ...
CM"o.J " _ .... J.l
(;or' ...........
E F_-.-
te
39
TYPES OF INTELLIGENT (SMART) PIGS: 'UT'
0_1001I_',
TYPES OF PIGS: 'UT' FOR WALL MEASUREMENT • Ultra sonics - A transducer transmits signa ls perpen dicular to the surface and receives signals from both internal and externa l surfaces • These pigs can generally only run in liquid lines , but can meas ure losses in much thicker walle d pipes. • Gives an absolute meas ure of defect depth.
Transducers
s=r=:::::::: ~.
-:=r=r=r;::: I
~_'IOOIl_'"
I
r '.., J 60
40
TYPES OF PIGS (WALL MEASUREMENT): 'UT·••• example
.J -J - - J 1- - -- -
--~~ . I, Sw>
t=======-~
Di.1>D« •
at
TYPES OF PIGS (WALL MEASUREMENT): 'UT·••• Sensors •
Typical perf ormance : • Depth acc uracy = +/- 0.020 "
•
• 95% confidence • Width accuracy = +/- 0.3" • l ength accuracy = +1- 0. 13" Requires liquid couplant
• •
10 /00 discrimin ation Standard UT pigs will not find cracks
82
41
TYPES OF INTELLIGENT (SMART) PIGS Combination ('Combi') Tools
C
2OJli_'
83
TYPES OF INTELLIGENT (SMART) PIGS Combination ('Cambi') Pigs _ W e can com bine technologies on a pig . _ For example, we can combine an MFL pig with a geometry pig:
Drive modu le
MFl
Deformation
Tool
Tool
Odometer
42
TYPES OF INTELLIGENT (SMART) PIGS Combination Pigs
--.-_.. ._<.. . . _-
85
TYPES OF INTELLIGENT (SMART) PIGS . Metal Loss & 'Crack' Detection ... 'TFI' MFL
86
43
TYPES OF INTELLIGENT (SMART) PIGS • Metal Loss & ' Cra c k ' Detection••• TFI MFL _ We can have cracks in pipe lines . stress corrosion crackin g. lack of fusion in seam welds , 'railroad' cracks, etc .. _ Our MFL pigs co uld not detec t axia l crac ks or narrow axial defects because of the orientation of the magnetic fiel d _ However, at girth we lds , high res . MFL pig can detect narrow defects, as these defects will disturb the mag neti c flux
_ If we turn the m agnetic field around 90 0 , ax ial defects will distru b the magnetic field
Transverse magnetic field
er
~---
TYPES OF INTELLIGENT (SMART) PIGS • Metal Loss & 'Crack' Detection••• TFI MFL •
TFI: Transverse Field Inspection • Uses MFl , but magnets are rotated 900 • Hence . MFL is app lied in circumferen tial dire ction • Data ana lysis can focus on seam weld • Give s full body inspection • Can also detect corrosion, but not as good as MFl
88
4
TYPES OF INTELLIGENT (SMART) PIGS - Metal Loss & ' Cr a c k' Detection••• TFI MFL Magnetic field
_ Therefore, axia l or narrow defects can be sized/found by TF I . Bul lhe defect must have a width to allow leakage of field
-"-
e 'rhererore it will not perform we ll on fat igue cr acks and
sec.
•
If
Magneti c field slightly disturbed by defects with no widt h, in this orientati on
"
/
T
-'>-
"
Magnetic field disturbed by _ defects with length, in this orientation .
89
TYPES OF INTELLIGENT (SMART) PIGS - TFI Accuracy
---,
m,_~
("'" _•••
!'"1--
Length
-_.-
Pig run in 2001 and 2002
- - - -- - - ---1
I:~ . 2
5"
•
-
•
Depth
/'
•.1_ / ' ./
_ c_ _
.... . . . _w ./
./
-/
./
•
O_'I\lOlI_ '1IoIIE_
-O-V-"''''''''r''_'"'_-w_
»
m
~
~
•
~
90 C_ _
_ _ 2003
~_SohoIy~
4
TYPES OF INTELLIGENT (SMART) PIGS - Crack Detection••• UT
O P. "". - 2006 R&<>6I'
UT CRACK DETECTION ('CD') PIGS: Principle _ UT smart pigs designed to measure wall thickness cannot detect axial cracks, as they 'fire' their sound into the pipewall at 90° UT SENSO R _ Bul if we 'angle' the ultrasonic sensors ' we can detect cracks
,.;.." " - - - - - . . . ,
92
4
UT CRACK DETECTION ('CD') PIGS: Types _ We have two types of UT crack tool : au ftrascn tcs (1) - Requires liquid
UT SENSO R
couplanl , detects all types of cracks (limits = depth 1mm , length 25SOmm). Available in diam eters 28" .
a ut trascn tcs (2) - UT sensor is mounted in couplant-fllled wheel* hence can work in oil and gas lines. Available in =>30" diameter.
WHEEL CON TA INING LIQUID ~~
C Pon__
2006R~6Il
93
UT CRACK DETECTION PIGS - Sensor Technology _Ultrasonic tools ope rate by introducing an ultrasonic pulse into the pipe wall at an angle such that it generates a shear wave trave lling circum ferent ially throu gh the pipe wall as it is reflected off the pipe's inside and outside diame ters.
_ If the pulse encounters a crac k, it is reflected back along the same path and is received at the transduce r. • By rotating the transducers by 900 , the tools can be mod ified to detect circum ferential crac ks and crac k like features. _ See API 1160 for more information
Pholog, ap/1
co u rtes~
of Michel Beller
94
4
UT CRACK DETECTION PIGS· Examples
-
"""-
Schematic of Pipelronix (now GE-PII) crack too l
-_..
-...~ .-
TYPES OF INTELLIGENT (SMART) PIGS - Crack Detection••• 'EMATS'
C_2006_.
96
4
TYPES OF INTELLIGENT (SMART) PIGS - Crack Detection... 'EMATS' • • Electromag netic acoustic techn ology (EMATl allows ultrasoun d to be generated in a steel pipewall.
-The EMATs do not have to be in physica l con tact with the wa ll. e l-lence, this technology does not require liquid cou plant to transfer the ultrasound into the steel.
_This makes it much easier to use in gas pipelines . e'Ihe EMATs generate a compression wave of ultrasound :
. it travels through the plpewall and reflects from surfaces. ethe returning echo produces a signal pulse in the transducer. eas in tradi tiona l ultrasonic inspection. the time between firing pulses and the ech oes determines the remaining pipewallthickness
_ EMATS can also dete ct coating disbonding
e_2OOI_
97 • ...........Iion 13""" '""" GE.f'lI _
TYPES OF INTELLIGENT (SMART) PIGS - Crack Detection... 'EMATS' .". _EMATS:.. Generation of Sound . A permanent magnet establishes a magnetic field in the pipewall and a coil generate ultrasonic waves into pipe wall. . The coil carries AC current at a 90 0 angle to the magnetic field e'Mirrcr ' eddy currents start to flow in the pipewall . A force normal to the pipewall is exerted on the eddy currents . This force generates ultrasound travelling through the pipewall The orignal EtJAT
rf;OQUirOO a high battery ~r lo drive it. mak.ing it impractieal tor pipeline inspection. Recenl advances in transducer desig n have redUODd power $8Il$Ol'
consumption requirements.
98
4
TYPES OF INTELLIGENT (SMART) PIGS - Crack Detection••• 'EMATS'
99
TYPES OF INTELLIGENT (SMART) PIGS - Crack Detection••• Eddy Current _Eddy c u rrent - low frequen cy magnetic field induced in pipe wall, inducing eddy currents. Se nsors time arri val of eddy current at back wall. 36" gas tine model expected 2003. • When an AC current flows in a coil in close proxim ity to a conducting surface the magnetic field of the coil will induce circulati ng (eddy) currents in that surface .
O
eail
_ When the eddy currents in the specimen are distorted by the presence of flaws or material variations. the impedance in the Eddy current coi l is als o altered. _ This change is measured and displayed in a manner that indicates the type of flaw o r material condition
Conductive material
100
5
MECHANICAL DAMAGE DETECTION PIGS?
",
MECHANICAL DAMAGE DETECTION PIGS? _ Mechanical damage defects are den is, gouges, or a dents with a gouge. _ Dents can be detected and measured using cal iper pigs .
_ New tools are coming onto the market to detect gouges .
_ These mechanical damages can have associated cold work and plastic strains . • Applied & res idual stresses affect the magnetization curve. wh ich then affect flux leakage. _ Similarly. plastic strains affect leakage
_ Consequently, MFL signals from mechanical damage defects are fundamenta lly different, when compared with purely a meta ! loss defect".
_ Note' " that the largesl co mponenl of MFL signa l from a dent is due to sensor ' tift-o ff" as they ride over the damage.
REUO\IEO
@@g
-............. _-__._._--,- - .,.,. -. ---- ---'- -.__ -.
~ ,_
.._......_ _...J_ .'__ T_.. _
"2
"-,.."
5
MECHANICAL DAMAGE: MFL Signals _M et al los s defects caus e high leakage of flux : _ this MFL signal is of th e ord er of 100s of gauss
_A gouge can consist of both co ld wo rked material & rretauoss: _ Cokl work. alters the magnetic properties of the line pipe steel _ It increases magnetic penneability in the area 01 the cerect . causing a decrease in magnetic flux
_ Metal los s increases flux leakage
_ Effed? The MFl signal from a gouge is of the order of 105 of gauss
_A dent contains resid ual strains
MFl
_ The residual stra ins win increase magnetic permeability _ But a dent causes very low magnetic flux leakage _ Effect? The MFl Signal from a dent is of the order of
105 of gauss
_Noise : The low MFL signals from dents and from gouges are a problem , as the MFL noise level is about 2 gauss O_.2OOlI_
Dent
(gauss) 100s 10s 10s
Noise
2
Metal loss Gouge
._ --- .._--- . ._.,--,--._--,_ .. _ _ _ _ _ _ _ _ •_ _ -=-
"3
MECHANICAL DAMAGE: MFL Signals _ The flux leakage signa ls from goug es and dents tend to have small peaks at the beginn ing and end of a damaged region , _ but the signals from removed metal have small valley s": REJdO\lf'D tlF TAI
DENT
GOUGE
~~~
_ Most mech anical damage defe cts are a co mbina tion of goug es, dents , and metal loss . _ The amoun t of removed meta l, a critical parameter in assessing da mage , can be obscu red by the residual stre sses and geometry changes assoc iated with dent ing and gouging . "s. _
_
" " " ' _. ..........
--"'.-
",.
5
TETHERED/CABLE/PROPELLED PIGS
105
TETHERED/CABLE PIGS/etc _ Some pipelines can not be pigged using the free flowing pigs, e.g : _ Some loading lines _ Some tie-ins
a t jnes with no traps _ These lines are co nsidered 'unpiggable'
106
TETHERED/CABLE PIGS/etc
_ Remember, 'unpiggable' pipelines may also be uncleanab le _ Cleanliness may be a problem
....----
TETHERED/CABLE/PIGS/etc
'"
---.
_ W e can use pigs tha t are prope lled along be hind an electric meter, or are pumped thro' a line . _ They can travel many km, and come in most pipeline
sizes. _ These pigs will usually be attached to a power supply or data acq uisition box via a cab le.
".
5
WHAT CAN SMART PIGS DETECT AND WHAT THEY CANNOT DETECT - Summary
'0'
DEFECTS AND SMART PIGS (from API 1160) (0 = DETECT, S = SIZE)
DEFECT .
METAL lOSS
CRACK TOOLS
TOOLS
GEOMETRY MAPPING (caliper) TOOLS
•
TOOLS "' FL · SR
MFLHR
ur
ur
CORROSION
0&8 1
D&S
D&S
D&S
D&S
C RAC KS - axial
NO
NO
NO
D&S
D&S
NO NO
NO NO
CRACKS· eire
NO
d3&s '
NO
0 &5 2
NO
NO
NO
GOUGE
Detections but no disc rimi nation as gouges
DENTS
d
d&,
LAMINATIONS
d
MILL DEFECTS
d
OVALITY
NO
I_No'DIOO""""m,,, ''''''
d&,
d&,
d
D&S
d
0
NO
NO
J _ Lowoo" C3>o 0 Moo" Um,,""O, Un, ..;. " . 00'_ 5 _ WTool " Eq",r-' W'n Ov.. ,tyM......."lI Ge.v C p""""," 2OC6Rov6l.
"~
d&,
D&S
0 &,
D&S
NO
NO
NO
0
d
NO
NO
NO
NO
D&S
0 &5 5
2 _ "'o,M""""" . . -"" • - L<>wo<
NO
{~
. . - """';"1190 Dog)
c... $ ..-.. Lim,,,", 0.- U n ~ ; ."' . So"""
6 · lomiOldb'\' too
""""'I""
""''''''.~ e
mOW _
, ."" ,,,,, ,,"" "Y th. "" ""no,,,
_" ._,~, ."" ",,"h"'''''d ._
5
'BEST PRACTICE "
'BEST PRACTICE" - USA a Liquid pipe line operator s in the USA inspect more than the required 'high consequence areas' a Metal loss defects are ide ntified usi ng high resolution MFL tools, acco mpanied by a geometry tool
MFL Geometry
IIFf +
aHydrotesting** was also used: a 13% of operators used hydrotesting _ 69% used high resolution pigs
69%%
13%
.. _
·
_
,
,
_
w
.
_
,
~
--".......-_-
..-_""""*""__
w
a During inspection of 163,000 miles. approximately 1 defect every 10 miles required remediation
.
"'C ...... _ _...
1 defect repair/10 miles
... . . _ . . ..
eoooo.-.~
"""~ ._e..
~.
5
'BEST PRACTICE-' - Western Europe _Liquid pipe line ope rators in Western Euro pe subm it inspection data to 'CO NCAW E' . In
2004, _ 11% of th e (no w) 36000 km system is inspected every year by metal loss pigs.
11 % MFL 8% Geo metry
_ 8% every yea r by geometry pig
1iIfIIIIt + 1iIfIIIIt
_ 3% by crack detection pig
_ In 2003 , 26% of the metalloss/crack ins pections w ere used in conjunction with geometry pigs _ T here we re no inspection s us ing crack detection tools only
_ Up to 2003, 21% of the 36000 km system has
79%%
21%
never been inspected using pigs 113 (M'
INTELLIGENT (SMART) PIG STANDARDS
'"
5
NEW INTELLIGENT (SMART) PIG STANDARDS . AP11163 . "In-Line Inspection Systems Qualification Standard'. August 2005. Ed. 1.
American Petroleum Institute
. NACE RP0102-2002 . "Standard Recomme nded Practice, In-Lin e Inspection of Pipelines", 2002 • AS NT ILI-PQ-2005
_
ONACE' 11 11 • •;., • • • ••• ,' • •
ft< E CO RROSIO i'l SO C IETY
. In-Line Inspection Personne l Qualification and Certification", ANSI.ASNT ILI-PQ-2005 115
NEW PIG STANDARDS: API 1163
.API 1163: this document covers the qualification of in line inspection systems. It assures: _ Inspection provid ers make clear and uniform statements describ ing their pigs' performance . Pipeline ope rators selects suitable pigs for his/her
conditions . These pigs perform correctly under conditions specified _I nspection procedures are followed before, during and after inspection . 'Anomalies· are described using common nomenclature
.The reported data and inspection results provide the expected accuracy, quality, etc. 116
5
NEW PIG STANDARDS: ASNT I L I·PQ· 2 0 0 S _ A5 NT ILI-PQ-2005 _ Gives minimu m requirem ents for the qual ification and certi fication of in-line inspection perso nnel. Per sonnel are: _ Tool operators (field reviews of inspection data for excavations or identifying lie in sites for multiple inspection passes _ Data analysts (uses in-line inspection data for the detection of feat ures and the position ing of those feat ures in the pipe line for reporting)
_ The standard give s three levels of qualification: _ l evel 1 (b'a,neeJ III Tool Ope rato r and Data Ana lys t
_ l evel 2
a t.evet 3 Level 1
Train ing
Ed uc atio n
Ex peri ence (mo nt hs)
(ho urs)
6
80
High school graduate or equivalent
Level 2
16
160
As above
level 3
30 (Oper ator) 36 (Ana lyst)
320 (Operator) SOO (Anatyst)
>2 years at university/co llege
C_2OOI_'
NEW PIG STANDARDS: NACE RP0101·2002 _NACE RP0102-2002
_ Outlines a process to plan, organise, and execute an il1 line inspe ction project. It include s guidance on: _ Tool selection _Logistical guidelines _I nspection scheduling _Data analysis and mana gem ent
cl_l'OOf>_'
'"
59
SHOULD I CONDUCT A PIG INSPECTION ON A NEW PIPELINE?
'"
BENEFITS OF A 'FINGERPRINT'fBASELINE' INSPECTION • • •
• • •
A final check on integrity and quali ty Claim s under the pipeline's warranty It also allows an operator to log defects reported during the inspection . On subsequent in-se rvice inspections these defects can be igno red A pig can detect a va riety of different defects in different orientations . We co uld use the data from the baseline ins pection , to help determine corrosi on rates from late r runs There can be a long delay between testing and commissioning . This increases the risk of co rrosion being present in the pipeline at the start of operation.
''0
60
PROBLEMS WITH A FINGERPRINT/BASELINE SURVEY
• A pig can miss defects, or incorrectly size them. • Can you 'compare' the results of a baseline survey with a later in-service inspection? • A pig can detect a variety of different defects in different orientations. • However, the prob ability of these defects. and resulting failures , occurring are diffICUlt 10 quantify . and henc e any benefit is difficult to Quantify.
• The only practical way (and the only impartial way) that the value of a baseline inspection can be quantified is to asses s its effect on the integrity of the pipeli ne. • There will be occasions where a baseline will be useful. others when it will not be usefu l O_2OOIiRo.l> 1
BASELINE SURVEYS - SOME GUIDANCE •
New pipelines will contain some defects • API pipe spec allows som e defects , A SM E 8 31 allows defect up to 10% belo w nominal wa ll thickn ess fro m tra nsportation , etc..
• The se defects may have escaped detection al tha pip e mill, or may have been introduced during transportation storage or construction .
•
However, some of these defectscan now be detected by the new generation smart pigs • Th ese pigs can de tect defects belo w 10%
wallthtckness. • In a thin walled pipe line this means that <1mm defects will be detected .
61
BASELINE SURVEYS - SOME GUIDANCE (c o n t .) •
In the extreme, a long pipe line that has been superficially corroded during - say - storage . and contains many thousa nds of sma ll internal corrosion pits. all below 1mm , will be condemned by a fingerprint run
• the smart pig will report 10,000s of co rrosio n defec ts in the pipe line' • however, thi s pip eline will have passed the pre-servic e hydrotest, contain defects th at are insignificant. and the defects de tected may be 'custom and practice' storage/construc tion defects allowed by
ASME. • we only know about them bec ause of the new smart pigs , but they have alway s been in o ur constructions.
BASELINE SURVEYS - SOME GUIDANCE (c a n t .) •
Old pigs wou ld detec t defects greater than 30% wt or later 20% wt . • Now, they detect <10%'u'Il.
•
Ther efore a pipeline that was fingerp rinte d using old techn ology , ana passed as 'defect free' (i.e. no defect above 20% wt ), ma y - on a new run today - have 10,000s defects reported, all under 20% wt. • The defects are reportable using new technology
•
Some may be categorised as seve re if simple defect sizing and assessment methods are used .
p ,peWa/I
Clustered profile
length
'"
62
BASELINE SURVEYS - SOME GUIDANCE (cont.) •
There is a need to quantify the 'workmanship' level of defects on a finger print run, otherwise perfectly acceptable new const ructio ns con taining 'custom and practice ' de fects , will be the subject of lengthy arguments betwee n operator and constructo r.
NACE RP 0102-2002 sta les: 'True baseline III surv eys , Le. those co nducted prior to or very shortly after the start of service, offer a number of benefits that may sign ificantly reduce the workload required following future surveys, but are not required:
,,,
PIG AND HYDROTEST COSTS
'"
63
INTELLIGENT (SMART) PIG COSTS _ The cost of a smart pig run will depend on the pig , the defects yo u wa nt to detect , the length of the lin e , acc ess, condi tion of line, et c __ No rules for estimating . _ The demand for smart pigs is great - suppliers may dictate cost
$1000/mile 3 An estimate in 2004 from a pigging company
2.5
2U
~~~
1 .5
was : ' S1600/mi!e for high res -$BOO/m ile for low re s (ig noring mo bilisatio n Idemobili sation costs)
1
D.5 D ~"'==
GEOMETRY
WT
CRACK
Pig type
OP-,,-,2005 ,..,G."
TO PIG OR TO HYOROTEST? - Can we p ig?
INGAA data for USA gas lines: Pigged
20-25%
Piggable with minor modifications
25 -35%
Piggable with extensive modifications
20·30%
Not piggable
15·20%
~ ~IJV" ' y
il.
128
64
TO PIG OR TO HYDROTEST? - Costs? In mo st large pipel ine systems (e.g. US A (oil and gas) and UK (gas)) >20% of the pipel ine s will be unpiggable Co st' US$ /mi le 20000
_The USA Office of Pipeline Safety have estimat ed" (2001 prices) that: hyd rates! costs $S,274fmi le (not inc luding repai rs). _ Smart pigging costs $3,210/mile (not including costs of modifications to allow pigging) _ (see next slide)
• H ITest
15000
_a
D Direct Assess o Pigging
10000 5000
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129
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TO PIG OR TO HYDROTEST? - Modifying for pigs IN GAA and AGA have quoted (2003 ) pipel ine modification
costs" INGAA Si mple mod ification (adding lau nch & receive trap)
,
Major mo dificati on (traps, pipe replacement, etc.)
$76,SOO/mile' "
Pipe line in urban are a ('LDC')
AGA
$11 ,7S0/m ile'
<$SO,OOO/mi le
.. 40 mile Ime •• , 10 mile line
II:> Po, ."., 200li R..6Jl
130
65
TO PIG OR TO HYDROTEST? INGAA and AGA have quoted (2003) hydrotesting and pigg ing costs" INGAA
AGA
Pigging/mile
$3 ,669
$9 ,660
(not including modifi cations)
(long distance
(in urban areas?")
lines")
Hydrotesting/mile
$29,700
$40,000
(nol including repairs)
(long distan ce lines)
(in urban areas )
Direct AssessmenVmile**** $ 15,000
....
__-
$7-8,000
ExcavatIOns, e.g kr " e<1ficallOn. can typoeally 00$1 be!'oW!en 529.000 and S40.ooo " ' Typocal l DC: shorter estaoce ~ nes •• Long dIstance line5 wiI typically be pigged between compressor stations. ~ e. 50 miles ..... ......-. • - . ' 50!. ...
......
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131
TO PIG OR TO HYDROTEST? - Techn ica l Illustration
DESIGN PRESSURE (72 pe,cent SMYS I
HYDROTEST PRESSURE ( 100 pe'cent SMYSj
" 0_2001_ '
.
.
" 2c1(Rt )" O.5 (no rmali••se d detect " lengt h)
j
.. .. .. '"
66
INTELLIGENT (SMART) PIGGING - Using the Data
O_JOOS_'
SMART PIGGING - Some Defect Assessment Considerations ~ 1 •
•
Pigs cannot disc riminate between all defects - the re will be con fusion with som e defect s. This m ay req uire excavation/uncovering for visual inspection of defective areas . • Work with the pigg ing company when interpreting data - they know the data the best. Ensure you unde rstand all repo rted feat ures. and ask for further interpretation if there are prob lems . • When pigging com pan ies are confused over a defect - it is your responsibility to determine the most likely defect. • For example, if a report says 'manufacturing or mechanical defect' you shou ld be clea r which one it is. • Has the pipe a history of manufacturing defects (e .g. has the pig reported ma ny of these defects)? _ Is the reported defect in an area where mechanical damage is likely to occu r, e.g. heavily populated area , shared corridor, pipeline crossing, etc . When in doubt - investigate!
0 _ 2 0 0 1 _"
'"
67
SMART PIGGING - Some Defect Assessment Considerations 2 a
•
•
•
Pigs are not perfect ... • Always check with the pigging company reoreliab ility. tolerances (depth , length), etc. • Add tolerances onto the report ed defect sizes .. . if a defect is reported at 20% wailihickness and the pig depth m easuring tolerance is 10% wall thickness , use a defect depth of 30% in your preliminary calculati ons. Pig companies may give you a defect ass essment (an 'ERF') to help you rank the defec ts' severity. • Chec k that the pig company has taken into account all stresses (e.g. axia l stresses), m aterial properti es (e.q. your pipeline may be low toughness) and defect interactions . When in do ub t - inves t iga te!
SMART PIGGING - Some Defect Assessment Considerations· 3 • •
•
Use ALL pipeline/inspection/operali onallhi storical data when con sidering a smart pig defect report . Compare your pig report with your pipeline map , and superimpose pi ~ defect locations. • Do defects co-i ncid e with heavily populated areas (this would mean high consequence of failures, and possi ble third party interference defects) , at low points (could be corrosion due to wate r settling), etc.. Are reported featur es near recent excavations (could be gouges ), at top of pipe (co uld be denting due to impacts), in field bends (COUld be wrinkles), along long. seam weld (could be SCC )? • Use aU known inspection data when reviewing pig reports previ ous inspections by other pigs may help current interpretations . • When in doubt - investigate!
C " - 2001\1lft6',
136
68
SMART PIGGING - Some Defect Assessment Considerations· 4 •
Location accuracies of pigs vary - check the pig company's specification . • A pig run one year may report a defect at a one loca tion . but in later years another pig may report the same defect at another location - but irs the same defect. • location accuracies are typica lly 1·2% from a fixed reference point • This means that if you have a pipeline feature that the pig can easi ly identify (e.q. a valve or a 900 bend) . it will be within +/- 1-2% from this point. • E.g. if my defect is 200 metres from a valve reference point . the pig shou ld be able to locate my defect 10 +/-4m (for 2% accuracy). • However, if my on ly reference point is a Tee that is 2km from my defect report, my accuracy is +/-40m.
Excavalelvisually inspect featu res that are potentially serious - e.g. if you have a report of a part wall defect at the top of the pipe . and a previous calipe r run has found denting in that vicinity. you may have a combined dent and gouge. • Wh en in dou bt - investigate!
•
SOME CASE STUDIES ON PIGGING
O_2OOIl_l
''''
69
CASE STUDY 1 - Use all Data•••• _40· diameter, 0 .344 " wan-ttnckness. gasolene line constructed in 1978 . _ Operating press ure at lime of accident = 384psi e c onetructeo at a depth of 4 feel , through an act ive landfill site . • Operator's construction specifications did not include special requirem ents for pipeline cons truction through landfi lls. _ Landfill material consistin g of trash and other materials extended to more than 10 ft deep at places unde r the pipe line _Th e section of the landfill whe re the pipeline was located remained in use unt il about 1980 , and was officially c losed in 1987 . _ Up 10 1980 additional debris was placed over the pipelin e . _ At the l ime of the accident, about 8-10 tt of debri s and earth covered the pipeli ne at the point of failu re .
",
•
CASE STUDY 1 - Use all Data•••• (cont) _2 weeks before the acciden t, a recycle plant near the pipeline began using an area over the pipeline to generate and stockpile 'mulch' , _ At the time of the accide nt. the mulch pile height was 17 fee t _ The centre of the mulch pile was over the pipeline, and - 60 ft from the point of failure. _ A heavy vehicl e occasionally traversed the pipeli ne right-ot-way while moving equ ipment around the site. _ Crossing the pipeline right -of-way with heavy equipment and storing materials on or nea r the right-of-way were against an agreement betwe en the operator and the recycle plant.
'"
70
CASE STUDY 1 - Use all Data•••• (cant) _ INSPECTIO N · Op er at o r ran a pipeline internal inspection t ool ("smart pig" ) throug h the p ipe line i n 1993 and found no significa nt anomalies. _ SURVElLANCE - The aeria l pipeline patro l pilot noted the mulch stock pile on the right-of-way dur ing pat rols , but did not believe this to be of concern _ He further believed that the appropriate operato r's em ployees were aware of the mulch pile on the right-of-way. _ VISUAL - 6 months prior 10 the pipe line failure, a 'conce rned c itizen' living in the community wrote 10 her cong ressman and expressed con cerns about the safety and vulnerabi lity of the pipeline in the landfill. Congre ssman wrote to the reg ional regulator (OPS) as king that to add ress these co ncerns , _ An inspector interv iewed oper ator personnel and visited the landfill sne. _ No cod e violations were noted by the engineer . _ The visit by the engineer was made prior to the activities of recyde plant and the mulch being placed on the line .
'"
CASE STUDY 1 - Use all Data•••• (cant) .Pipeline failed in 1998 evlsual examination of the pipe segment revealed circumferential buckl e deformation on the upper side of the pipe. _N o damage such as dents, gouges. or corrosion was noted on the outside surface of the pipe in the area of these cracks.
_ Cracking in the pipe was consistent with stress dam age due to soil settlement underneath the pipe .
71
CASE STUDY 1 - Use all Data•••• (cont) aprobebrc cause of the pipeline rupture was : _Selllement of soil and compacted trash underneath the pip eline .
_ Contributing to the pipeline failure wer e: _ Act ivities of the Recycling Centre, which subjected the pipe line 10 additional stresses at and near the site of the rupture , and _The failure of the aerial pat ro ls 10 report 10 the operator that recycling activi ties were ongo ing on the pipe line right- of-way _
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CASE STUDY 2 - Use your Defect Assessment Knowledge•••• _2 4",0.25", crude oil line , constructed in 1975. Pressure = 606 psi .~~::!!:::::~~] . I n 1997, a MFL standard inspection tool was run throug h the ent ire pipeline. _E xcavations were made allocations where the tool indicated significant anomalies. _ At the site whe re the pipe line ruptu red . the 1997 inspection data showed an anomaly that the contractor had interp reted as a "dent.~ _T he pipeline had not been excavated at this location because the dent did not appea r to meet the repa ir criteria being used at the time. _ Repair criteria was .. repair if de nt was :>2% of the outside diamete r of the pipe .
t===::==~I . Failed in 2000. $7million costs
,,,
72
CASE STUDY 2 - Use your Defect Assessmen t Know ledge•••• (cant) _The rupture was on the bOttom 01the Pipe. • Transgranolar crack s thai had the appearance typical o f fCitigue progression were present. • The combined depth of the progressive cracks in the areas o f ma ximum penetration was about 90 1095 percent of the pipe wali l hickness . Primary and secondary orig in areas of fatigue cracking 'Here found at the edges of a dent in the pipe wall. _ The dent was cons istent with con tact with a hard object altho ugh no hard object likely to have caused it (such as a rock) was found during the investigation. _ Numerous secon dary cracks were in the vicinit y of the two orig in area s. _NTSB Conclusion: pipe failed due to fatigue crack ing _This wa s due to a dent in the pipe that. in combin ation with fluctuating pressures within the pipe . producing high loca l stresses in the pipe wall
'"
CASE STUDY 3 - Pigs will not detect certain defects•••• _197 0 Gasolene pipeline. 28". 0 .281 ~ . 705psi operating pressure at location of failure. _ An in-line inspection tool ("smart pig") was run through this section of line in 1997. _ Anomalies meeting the operator's criteria were excavated . evaluated. and repaired. - No anomalies meeting their criteria were reported in the area of the 2000 failure. so the pipe was not visually examined at this location. _ Failed in 2000. S1 8m itlion clean up/dam age bill
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_
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'"
73
CASE STUDY 3 - Pigs will not detect certain defects•••• (cont.) _The NTSB concluded the proba ble cause of the pipel ine failure wa s: _ Corrosion_lo w cycle fat igue cracking tha i initiated at the edge of the longit udinal seam weld at a likely pre-existing weld defect. a Contributing to the failure was the loss of pipe coa ling integrity.
---.....,.-
. . . . ., . _ _ ....... -<1)
CASE STUDY 4 - Pigs will not detect everything•••• a12.75", 0.2" fue l oil line. Built in 1972- 3 a1995: Inspe cted by a geometry too l & MFL 1001. aThe data from the MFL inspection did not corr elate well with field measurements for either wall loss dala or odom eter readings. aThe oper ator decided to do an additional inspection in 1997 using an ultra sonic inspection (UT) tool a 1997: Inspection using UT too l + pigger used a cal iper too l to confirm that the re we re no obstruct ions 10 prevent passage of the UT too l. _ After excavat ions , operato r det erm ined that the pig inspection data correlated relatively welt with field m easurements • However, some locations had large r corros ion than indicated by the UT _Failed in 2000 . $71m illion clean-up bill.
'"
74
CASE STUDY 4 - Pigs will not detect everything•••• (c o n t) _ The pipeline ruptured at a wrinkle in a section of pipe that had been fieldbent during initial construction of the pipeline in 1971 and 1972. _The deformation , or wrink le , that failed was a sing le outward deflection of the pipe wal l, commonly described as a buckle.
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CASE STUDY 4 - Pigs will not detect everything••••(cont) acause of failure :
Pressure/Temp
_During service, forces imposed on the defor med area of the bend, including the norma l operating pre ssure and therma l cycles in the pipe line, caused repea led stra ining and eventual crackin g until the pipe at the deformed a rea fa iled. econtrtbutlnq to the magnitude of the fuel oil release were inadequate ope rating procedures to ens ure timely leak detection.
_Suckle was undiscovered beca use the data from the in-line inspection too l were interpreted inaccurately as representing e r-otece.
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75
ADDITIONAL INFORMATION
-
DEVELOPMENT OF PIGS
THE HISTORY·
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76
DEVELOPMENT OF PIGS - THE HISTORY*
Development tlrfi r~1
" n pipdint., ..cra ppe r
Dev elopment of
SHWr U : lt l'l u l: ~i n g machine b~ T il"
Tubosupe
lIfi()
1'J."1l
1"'7~
Forma ncn urG ent" 'a l Ilc \caling Cu . 1'1.: Inld li::l.'nll'i g Ile\l:l"pmcnt [Tubucopc - Lia nlug \\1 1.10), Mrs "PH
19sn
Brilhh Ga..1 BMflle a\\C"m,'lll or manrri al prepcrue.. & f3i1U rl', 711'..
0(' , etopmcnt (If I 'h nl \ onk Firs t in..talla rion (If Clur k Spring "
I W.S
I%U
.v ppr ova l of I S "alural G'l" Pipeline S,.f<:ty .\ (1
- - - - , (101(j'IIn-E rnn i, ), SO', Dn cl npmCllt of s ec I Ll
1989
1';'IS
no r IIp ,, n,, III lin
1. w l, 91)' .. \
Ih-n lopnll'nlof l'el roSleen ' 1I repair- techniques
© Penspen 2006 Rev6/1
I>c Hl upm cnt nf foa m pig " Pul l pilt
usc «r Cloc k S prings
\C1I Safdy Hill appruved hy I S Se nate
' Mo Mohitpour et at. T rends in Pipeline Integr ity Inspection And Rehab ilitation Tech niques', Proc eedings of 4th Internat ional Pipeline Conference September 29-0 ctober 3 , 2002 , Calgary, Alberta , Canada, Paper IPC2002-27035
PIGGING TO MAINTAIN EFFICIENCY • •
•
•
• • •
C_
R
Consider a 12 waterline: If inside diameter is reduced by 5% ( 15mm), the loss of throughput is 10% . To bring the through put to the origina l level would require an increase in pressure of 30%. If deposit was uneven, resulting in turbulent flow, effe ctive reduction is 15%. Through put would be reduced by 35%. Increase in press ure to overcome losses wou ld be 140%. On the BP Amoco Forties pipeline. friction increased by 4.2% per day if the pipeline was not pigged.
2005 _ '
" 3
MFL PIGS - 'SATURATION' and 'LEAKAGE' Steel can carry up to a 1000 times as much magn etic flux as air or liquid
:/ /
Magnets on pig saturate the nominal pipe watl. The nominal wall can carry no more flux
co .......... 200II ~ ..w 1
-.
I /
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~
W hen there is a reduction in t he p'pewan, the flux density would have 10 increase in the reduc ed prpewall - but it cannot as it is saturated .
Hence , the flux leaks out to the air, and sensors on the pig detect this leakage.
,,..
77
OPERATIONAL RESTRAINTS - MFL PIGS •
WAll THICKNESS •
The MFL pig creates mag netic flux through the ouewsn • the pipe steel mu 5l: be saturated ""til magneli(: nux to a llow inspection. • the Ii&Id level woll reduce as !he wa ll th itk ness onctea1l6s. • l'M:!noe lhe re is a max imum wa lllh'clcne ss that can be satisfactorily ;nspeded ThICker ....all ,..;11 not be seneaied
•
Magnetic nux pigs are limited by walilhickness. • Typ ically up to 18 m m w ali l hic knes s up 10 16 in. diameter, arid 30 mm for greater tha n 16in.
•
SP EED • •
•
When the pig is stationary. we have the ma ximum mag netic flu x level in the pipe wall . As the pig 's speed inc reases , the flux level reduces du e to the effect of secondary magnetic fields arising from eddy cu rrenls induced by the mot ion
HISTORY •
The first run by an MF L pig can give different mag netic field levels co mpared with later runs because of magnetic 'hysteresis'.
•
For very thick wall (I'.ith low field levels), an inverse history effect has bean observed more passes may be needed to ach ieve an optimum,
• In general, the Iirst pass induces higher field levels than later runs,
•
C_
SIZE • • •
There are MFl pigs on the market that can inspecl 6-56in diameter lines Most can detect general corros ion, pittmg, girth weld cracking. and dents Can detect metal los s down to 10% wall thickness, Of smaller
2II06_,
is
PIG TRAPS · Details _ Pigs are launched and received in 'traps' _ ThoS(! are usually made out of pipe 2" diameter above the pipeline size. _ Smart pigs are longer Ihan utility pigs and need longer traps _ Traps shoold be able to ceereoce at r,~ 1 valve.
ta~e pig
with about 05 metr e clearance
at pig door, and 05 metre
_ Launch trap mu st be able to take full length of sma rt pig, therefore the 'barre!' leng th is cnncal.
e neceoe trap must be
able to accom modate the pog berweentne last valve and the end of the 'reducer', The plg should flOItr avel up the barrel. as it loses propu ls ion in larger dlameter Hence the length of the reducer plus distance to r,~t valve weld is cotcai. _ Valves around pig trap must be
v,or~ing .
and seated' If they are paSS1f"1Q gas/oil. the p'9ll,ng
cannot commence Check all valves'
_ Traps reee 10 be purged ....\h nltrogen. Have a (say two boItle) supply lor each pig run avaIlable . _ Ass istance wiI be needed \of pig compan....s at pog trap Sll e 80lh in terms of cranegatworl
_ Beware of pig trap debns - it can be tolOC and inflamma ble, or radooactrve, or
conta,n~ ,
etc...
78
POWDER (DUST) IN PIPELINES
C Porsor 2006_
'
'"
POWDER (DUST) IN PIPELINES _ Gas pipe lines will co ntain 'dust' from construction, etc .. _ W e do not want dust in ou r gas stream - it will block filters and can damage compressors .
_ It can also block the passage of pigs. or foul pig sensors _ Some 'dust' is caused by corrosion and/or the presen ce of sulp hur in the gas :
. 'Black' du st (see next slide s) • 'Yellow' (elemental sulphur ) dust
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_ This is no t well und ers tood
e v enow dust is depo sition of elemental sulphu r due to desublimatioo of sulphur vapour in the gas stream . Pressure reduction s can ca use the powder to form . This sulphur can be in very small (e tppm] quennuea in the gas . _ The Australian organis ation - APIA - is conducting research into this type of dust
'"
79
BLACK POWDER (DUST) IN PIPELINES _ So me 'dust' is gas lines caus ed by corrosion or the presence of sulph ur in the gas _ Slack powders (usu ally iron sulfid es and oxides) are known to be created inside na tural gas and oth er similar wells and pipelines. _H ydro g en su lp hd e and su lphr are th e major cause of bl ack dust
_ T he com ponents and conditions necessary to create this dust can be found at some point in many pipeline s. Some form of iron sulfide is known to be cre ated by either of two me chani sm s: a ch emt c e! re actio n of constituents present in the pipeline, usually hydrogen sulfide. and e ml crcbtet assim ilati o n of chem ica l constituents in the pipe and the production of both iron sulfides and pipe wall pitting,
_ The iron oxides are created from subsequent ox idation of the sulph ides. or by direct oxidation of the iron in piping .
'"
BLACK POWDER (DUST) IN PIPELINES ' _ Slack Pow der is a generic nam e for sma ll particles of ferrou s corrosion by-produ cts . _ The material ma y be wet and hav e a tar-like appearance, or it can occur as a dry, very fine powder tha t is alm ost like smoke . _ Slack Powd er can be any of seve ra l forms of iron sulphide or iron oxide .
_ It may be mechanically mixed or chemically com bined wit h any number of contaminants such as water, liquid hyd rocarbons , salts . ch lorides , sand and dirt . 'Black powder"is often used as a generic term for debris consisting of a mixture of iron oxides, sulphides and/or carbonates. The industry normally associates this black powder as debris is gas lines. but its main constituents are present in other lines. The typical causes of black powder are: -Direct chemical reaction of transported fluid components with pipe alloy. -fnerrecuve removal of mill scale from new pipe during pre-commissioning. -rmproper dewatering, drying and/or lay-up of pipe during pre-commissioning or remedial works. _
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80
BLACK POWDER (DUST) IN PIPELINES _ It is not well understood .
a s ome pipelines have black powder problems and others do not. _ It appears that those lines that do not have the blac k powder problem belong 10 smaller co m panies who do not cover a large area and whose opera tions are closer to the distribut ion end than 10 the gat hering end of the pip eline ,
• Black dust
on16- cleaning pig
_ Slack powder is claimed to have occurr ed in both "dry" and "wet" lines _ Even in paralle l lines , one can have the problem and. the other not . _ A report by the Gas Mach inery Research Council (R M BaldwinBlack Powder" In The Gas lnoustry - Sources, Charac teristics And Treatmen t', GMRC Report No. TA 97-4 . 1998) stated . 'We have not identified any pipeline to date which has been able to eliminate tne black powder problem once started.'
te
HOW IS BLACK POWDER FORMED '? _ Black powde r is fo rmed from a chemica l reaction between the ferrous pip e alloy and constituents of the product _ Microbial action can aid the chemica l reaction _ Hydrogen sulphide, carbon dioxide and water can co ntribut e the formation of iron oxides, sulphides and carbonates - H2S is common in gas gathering lines. but is reduc ed in transmission lines afte r processing the gas _ The presence of oxygen can increase corros ion and create oxides _ The presence of wate r is important to aid the prdiuction the the powder. _ Sulphate reducing bacteria and acid producing bacteria can cause blac k powde r Int ern al c oati ngs on a new line can p revent b lack dust in service
11_2006_""
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RI
BLACK POWDER (DUST) IN PIPELINES: Cause _ Black powder is very common in gas pipelines all over the world. and can cause wides pread prob lems in equi pm ent fouling and flow reduction"
_ It is caused by" : _ Sour gas service: high revers of H2S ca use formation of iron sulphides _ Moisture: water in wet gas , or left ove r from the hydratest leads to the form ation of iron hydroxides and iron oxides _Mill sca le deterioration : in older and uncoated pipelin es mill scale may be poor quality and it can disband du ring manufacture of the pipe. Often in combination with moisture, this can accumulate in crac ks and pores in the steel, and lead to black parti cles. Black powder presence may also increase corrosion rate in a line by offering a
suitable environment for SRBs to thrive in, or by preventing corrosion inhibitors thai are dosed into the gas stream from reaching the surface of the metal surface in order to protect it".
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' OJ
BLACK POWDER (DUST) IN PIPELINES: Effect " _Slack powd er can: _ Reduce the efficiency of the pipeline . Ieads to flow losses in long pipelines . clogs instrumentation and valves; _ Reduce gas quality; _ Fouling/dam aging/wearing of equipment (turbine blade s), filte rs,
etc .: e reduces erncrency of compressors _ Fill defects and as they are made up of ferrous materials they can mask the true extent of defects detected by MFL pigs. _ Fouls intelligent pig sensors and builds up in fro nt of the pig The weight of smart pigs such as 'MFL' pigs, com bined with the small clearances and stron g magnetic fields ma ke these tools particularl y prone to becoming 'clogged up' with Black Powder " C-'-2OOli 1l_,
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H2
BLACK POWDER (DUST) IN PIPELINES: Removal " _ Black powder problems can be solved by:
_ Mechanical pigging _ Gel cleaning
.Filtering
esurtactanr- cleaning
C_
2006 -.to·l
.... _ ._F..,..,......_ ..
& O" _ _
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REMOVING BLACK POWDER " _It is beneficial to use a combination of seve ral cleaning pigs in a long train, separated by a fluid (e.g. a gel) to suspend and transport the debris that the pigs leave behind _Another very effect ive method of removing the powder is cleaning with inhibited acids _ But this method produces toxic H2S and dispo sal of the acids may be difficult. and _ Is not practical for long lines with extensive debris. Brush or scraper pigs can remove the black powder by loosening it, and pushing (bu ll doze) it along the pipeline. Howeve r, due to the specific gravity of the powder, and if it is in high volumes, the pigs may ride over a lot of the dust, leaving much behind .
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"6
83
BLACK POWDER (DUST) IN PIPELINES: Control _It is usually controlled/reduced by filtering the gas _Some pigs claim to remove black dust _New method of controlling the powder is by injecting a chemical to eliminate the dust
Dust on 12"
cleani~ g',",g"''''
'"
HOW MUCH BLACK POWDER CAN BE IN A GAS LINE'? _Slack powder can be in a variety of forms; dust, flakes , molasses,grease or wax. _Slack powder can be extensive, and theamount removed can be measured in tonnes rather than kg. A case study' quoted 127 kgJkm (450 Ib/m ile) of debris removed from a pipeline _Two case studies" quo te the removal of 20 ,000 and 60,000 kg 44 ,000 and 136,000 Ibs) of debris _Another source quotes up to 226,796kg (500,OOOlb) of black powder rmeoved from a pipeline using 'physical' methods'?" . This suggests that pure ly 'chemical' methods to remove Black Powder may be impractical Gas specifications for H2S , CO2 and water can be quite 'lenien t' Just 1ppm of H2S in 10MMCFD gas can produce 363kg of black powder in a year"
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84
BLACK POWDER: Summary _ In many cases, black powder problem s are considered a way of life that has no solu tion and therefore is accepted as one of the problem s and expense s of doing business . - Once you have a black powde r prob lem , it may not be possible to solve it..; _ The formation of the powder can be mitigated by': elntemal coatings on the pipeline; . Reducing the concentrations of H2S and CO 2 in the transported gas; _ Swabbing the pipe interiors with btocldes and/or cor rosion inhibito rs. _ The powder can be removed by a combination of mechanical pigs and debris-suspending fluids " • This pig/fluid combination involves a train of severa l pigs and fluids
MANAGING AN INTELLIGENT PIG RUN •
Techn ologies: • choose from MFL, ultrasonics, etc.. • choose resolution
•
Track Record and Cost:
•
Pre-surv ey Meet ing :
•
line Pro vin g and Cleani ng:
• assess this usin g past use rs, or seek specialist advice • es tablish need and notify pig suppl iers • pigs to chec k gauge (to prevent pig jammi ng or being damaged) • cleaning pigs (e.q . a mag netic-cleaning pig to remove ferrous debris prior to a MFl run, or wax cleaning) - BEWARE THE STUCK PIGI
•
Time: • the results of a geo metry survey may only take several hours but the results of an intelligent pig run may take seve ral wee ks. • Some smart pigging companies can give you the 'top' defects within 48 hours
"0
FINDING PiGS•••• • Pig SIGN ALING : a method that indicates when a pig has reached a certa in point • e.g. a lever • You will need a pig sign aller at the lau nch and receive locations . 8 9 an intrusive level thai the pig lifts.
• Pig s can cont ain a magnet or radioactive source that can be detected externally (non -intru sive )
• Pig LOCAT ION: a method to determine where a pig is • e.g a transmitter in the pig , that can be located using a receiver
• Pig TRACKING : a method that follows a pig along a line • e.g a series of transmitter s. or acoustics
IN-LINE INSPECTION - KEY DECISIONS AND FOLLOW-UP SERVICES
>-
ow
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(j)
How ofle n 10 insp ect?
W
o
(fJ
accuracy, cost;? Wha t do)'OU
When to inspect?
(fJ
ii:w
Whi ch pig to use (Qualiry , reliab ility ,
Wh ich line 10 inspect firs t?
Fitne ss-for -purpo se Assessment of Defects Detected and Futu re Inspection Need S
,,
wa nt to detect?
\
Wh allo do WIth De fecls not detected
Sa fety Assessm ent (of Current Operal/Ol1 or Uprating. Revalidation)
C_2006_,
86
PIG MARKET AND SUPPLY •
In the utility pigging and service portion of the industry, there are probably less than 50 compani es worldwide .
•
In the in-line "sm art pig" port ion, there are only 5 or 6 major companies prov iding the m ost advanced pigging technology and serv ices.
•
Th e world ma rket for both utility and smart piggin g is estimated 10be >$550 million with the smart pig portion being an esti mated $450 million . J C Cakl ",el l, 'PIggIng world ' S~lc ty Are na, Marcl1 1009 Vo1. 82 No 3
Pipe LIM
•
The Inter state Natural Gas Association of Ame rica (INGAA) esti mates that 25% of the USA natural gas system has been intelligently pigged since these pigs became generally available in the 19805
•
Half the Class 3 and 4 gas pipe lines in the USA are not piggable without extensive retrofits, ' P~ ..
lnle9"'Y ManaQ"""",1 ,n HoQh ConHQYeOCeAJeas'. Dod
PIG MARKET AND GROWTH Km surveyed/year 6000 .,,-- - - - - - - - - - - -
5000
19% of system
inspected in this year Meta l loss pigs. <, 31000km Wes tern European oil system www.concawe.be
4000 .jj---
-
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o 1978
1983
1988
1993
1998
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87
OPERATIONAL PROBLEM· STUCK PIG • • Pigging co mp anies will ask ope rators to be responsible for t e lf pigs , once they have laun ched them into the pipe line. _ However, pigs can st op in a pi pel ine and cause pro blems - this can lead to liabil ity argum en ts . _ Soth the operator and pigging com pany ~ I can be at fault, depe nding on reasons ~~:~ '~>t for the pig being stuck.
I
20"cleaning pig stuck in line
OPERATIONAL PROBLEM · STUCK PIG e 'There is a difference between a 'stopped pig' and a 'stuck pig'. _ A 'st o p ped ' pig may be due to a pressure drop, or slight re duction in bore in the pipel ine _ The stop ped pig can be made to mov e by relatively mino r changes to pipe line or pig parameters (e.q . increasing t he pres sure) _ A pig ca n be 'st uc k' as a res ult of : . pipeline bore reduction - gauge/profi le/dumm y pigs are run to prove the pipeli ne bo re, to pr even t this. Examples of liability : _ if this 'proving ' is done by the pigging contractor, the stuc k pig is thei r prob lem , _ if the pig is stuck in a ha lf opened valve (opened durin g pigging by the ope rator), it is the operator's problem , _ gas flow con ditions - the re com me nded flow rate s sho uld be m aintained with adequate diffe rent ial press ure before/behind the pig, _ a pig fault - pigs operate in a host ile environment and can be dam age d - main item s that cause prob lems are typi cally cu ps an d suspension whee ls/assem blies . • Pigg ing com pan ies will produce many excu se s to minimise the ir liability in this case
'"
88
OPERATIONAL PROBLEM· STUCK PIG
_ This problem is avoided by runninq".. . _ cleaning pigs through the pipeli ne first, followed by 8 ...
_ gauging pig fitted with a deformable metal disk of the same diameter as the inspection pig. The gauging pig can also be followed by... _ a profiling pig, which is again a deformable simu lation of the expensive inspection pig.
_If these pigs pass through the line without
damage, the inspection pig will also.
C_2tll6_,
r-see GE-PII
webSltlfs 'faqs'l
m
OPERATIONAL PROBLEM· STUCK PIG
_If a pig does get stuck it can sometimes be
dislodged by -I ncreasing the pressure across it, eith er by raising th e pressure behind it or red ucing the pressure in front of it. - Sometimes it can be freed by sending another 'rescue
pig' behind it to push it out, assu ming the problem is damage to driving seals on the origina l pig. _ The final resort is to decommission the line and cut the pig out
'"
89
-r
~•
DO MFL PIGS DAMAGE INTERNAL PIPE COATINGS?
_Mag netic inspection pigs are heavy and fitted with steel brushes - These brushes may look like they would scrape internal coatings off a pipewall, they do not. _The pig weight is spread over thousands of individual bristles, and as a result the 'point loadings' are small.
H9
coPon"""n 2000 R",€I1
see the GE-PII website for more QuestIons 8. answers
DO MFL PIGS PERMANENTLY MAGNETISE PIPELINE?
THE~
~
_After inspection with a magnetic inspection pig, the pipeline is usually left in a state of low level magnetization. _ This can affect welding, if a section has to be cut out and replaced . _ In this case, de-magnetising proced ures are available to overcome the problem.
'80
90
SMART PIGS REPORTING & IM M EDIA T E ACTIONS - API 1 1 6 0 _ REPORTING - AP I 1160 suggests "final'pig report should be with operator WITHI N 6 MONTHS _ IMMEDIATE REPORTING - However, some defects should be reported as ' immediate concern' in a 'preliminary' report WITHIN 30 DAYS if they are: e o erecte of depth >80% of nomin al wall, regardl ess of length _ ACTION · These defects will require further monitoring. leak clamps , pressure reductions, etc.. _ The fa ilure pressure of reported defect is less than Maximum Operating Pressure of pipeline _ ACTION · Pressure reduct ion may be needed (with sim ilar reduction in pressure relief devices, etc.), etc.. _ Top of the line dents (between 4 and 8 o'clock) with any indicated meta l loss _ ACTION · Pressure reduction may be needed (with similar reduct ion in pressu re relief devices. etc.), etc.. _ Any other 'sign ificant" defect by a criteria of the operator _ IMMED IATE ACTION S - These actions are based on the in-lin e inspection report. and NOT exca vation _ We cannot wait for excavation to confirm or otherwise these serious defects _ These temporary actions must be in place WI THIN 5 DAYS of receipt of the preliminary pig report. They remain in place until excavation and assessment is completed. _ The actions remain in place until permanent measures are put in place WITHI N 30 DAYS of receiving the prelimi nary report
'"
SMART PIGS REPORTING & NON·IMMEDIATE ACTIONS - API 1160 _ REPO RTING · API 1160 suggests 'final' pig report should be with operator WI THIN 6 MO NTHS _ IMMEDIATE REPORTING· Some defects should be repo rted as 'imm ediate concern' in a 'prelimin ary ' report W ITH IN 30 DAYS (see previous slide) _ Other defects must be evaluated, repaired. etc.. within 6 mo nths of rece ipt of the final p ig report if they are: e beu s with metal los s or containing welds _ Top of the line dents (betwee n 4 and 8 o'clock) with dep th in excess of 2% pipe diameter (=>12 " diameter pipe) or 0.25" «1 2" diameter pipe) _ Dents with depth >6% pipe diameter - Gouges Of grooves of depth> 12.5% nominal wall thickness _ The safe operating pressure of reported defect is less than Maximum Operaling Pressure of pipeline as calculated using a safe procedure, e.g. ASME 831G. _ Metal loss of depth> 50% oominal wt a f()(eign line crossing _ Metal loss of depth> 50% nominal wt With significant circumferential extent (I.e. liab le to failure unde r axial loading) _ Weld defects of depth> 50% nominal wt a foreign line cros sing _ Possible cracks, that on excavation are cracks _ Selective seam weld corrosion
'"
91
DEFINITIONS
C ~ 2OOI _ '
"3
r:
DEFINITIONS: 'FEATURES', 'ANOMALIES', etc.. _ ANSIIASNT ILI-PQ-2DD5, NACE RPD192-200 2 and AP I 1163 give guidance on term inologies in pig report s: _ A 'feature' is any object detected by an III tool du ring the performance of an inspection run. A feature may be an anomaly (see next bullet ), valve, nearby meta llic obje cts, etc.. _ An 'anomaly' is a poss ible deviation from so und pipe material or weld. • "Mel al loss' is any number of types of anomal ies in pipe in which metal has been remov ed from the pipe surface. usually due to corrosio n or gouging.
184
92
DEFINITIONS: 'DEFECTS' . 'IMPERFECTIONS' _ ANSIIASNT 11I-PQ -2005, NACE RP0192 -2002 and AP I 1163 give guidance on termi nolo gies in pig reports: _ An 'imperfection' is an anomaly in the pipe that will not result in pipe failure at pressures below those that produce nominal hoop stress equal to specified minimum yield strength of the pipe material. That means an anomaly with characteristics thai do not exceed accept able limits _ A 'defect' is an anomaly for which an analysis indicates that the pipe is approaching failure as the nominal hoop stress approaches the specified minimum yield strength of the pipe material. This means an anomaly with dimensions or characteristics that exceed acceptable limits.
0_200&_,
'"
SETTING A SAFETY MARGIN· HYDROTEST AND OPERATION
HYOROTEST
TO 100%
SMYS
Safety Margin 0 ",tres s
OPERATION AT 72% SMYS
'X Safety Margin
IX
A-2 0% WT DEF!=CT COU LD SUR IVE
Safety Margin On defect si ze
A-40%WT OEFECT CO ULD SURV NE
So, we'll only accept defects in our 72% SMYS line mat will survive 100% SMYS (hydrotest) C_2006-.n
'"
93
METAL LOSS INTELLIGENT (SMART) PIGS Performance and Data Interpretation
METAL LOSS INTELLIGENT (SMART) PIGS - MFL & UT • MFL: • • • •
•
UT:
Diameters up to 56 " Velocity best u.s-anvsec Pipe/wa ll thickness>15 Max wall thickness
• Diameters up to 56" • Veloc ities up to anvsec • Wa lllhickness>7mm • Max wall thickne ss
• <=10" diamete r. OS"
• No prac tic al limit
• >10 " diameter __1 to 1.5"
• Range: • Up to 150 km for =<10 "
• Range : • 90-900 km
diameter • Be tween 14 0 and 800km for >10 " (seam less is less, and large d iam eters are lowest)
• Location• Ax ial is +/- 200mm from re f we ld • Circumfe rent ial is +/- 5 deg
• Location ' • Ax ial is +/- 200mrn f rom re f weld • C ircumferential is 0.3-0.5" {senso r spaci ng}
'8'
94
INTELLIGENT (SMART) PIGS - Data Interpretation . Pigs record data - they do not interp ret _ e.g. MFL pigs measure flux leakage NOT defect dep th and length _ The data is processed by software and viewed by anal ysts (human beings) . They will attempt to discriminate between corrosion . metal los s and manufacturing defects, by looking at the signal characte ristics (shape. amplitude, length, etc.) . _ It is not always easy! _ Therefore, som e co mpanies are moving to the use of more sensors on thei r pigs to discrimin ate _ This is being partl y driven by the need to identify 3rt! Part y Damage clearly. _ If you have doubts over a pig report. or do not understand the report : _ Clarify with the pig supplier a u se all your own data (maps, maintenance reports . etc.) 10 help clarify _ If in doubt, investigate e _ _ ~_,
'"
95
Pipeline Repair and Rehabilitation
Penspen Integrity
,,"......' 1
IMPORTANCE OF REPAIR AND REHABILITATION •
In many cases oil and gas field infrastructure is at the end of its design life, but they still have 25 or even 50 years of world production left.
•
Russia: 7% of its system is <10 years old. 34%>30 years . • Pravda , 2003 : They require $US 130million/annum to be kept in wor king order.
•
Over 50% of the 1,000,000 km of USA oil and gas pipeline system is over 40 years old.
2
IMPORTANCE OF REPAIR AND REHABILITATION _ Our pipelines operate in a hostile environm ent ... dam age and corros ion. _ Our pipeli nes ar e ageing ... corrosion. _ Our pipeli nes are being asked to operate longer ... for econo mi c rea son s _ Our pipelin es ar e being asked to operate long er ... we have extensive oil and ga s reserve .
3
REPAIR AND REHABILITATION - Safety Fi rst! • Safety is always our first consideration . • Pre ssur e reductions , excavation safety, trench safety , welding safety, pipe movement safety, fire prevention, emergency procedures. etc.• are our primary concerns.
-
,
,
-'" :?-
• Use recogn ised , pro ven proce dures, and qualified personnel, and ma ke use of relevant standards • e.g. API RP 2200
,
2
RESPONSE TO DISCOVERING DEFECTS 1. Reduce Pressure • reduce pressure to safe level and plan pressu re reduct ion s for repair/rehab ilitation .
2. Critical Information • Estab lish c ritical informati on for engi neering assessment.
3. Defect Assessment ~ 'Fitness for Purpose' • Carry out engi neering defect assessment, or structura l assessment if defect/dama ge is structural, e.g. loss of sup port, buckles,
etc. 4. Location Assess ment • As sessment of dam age location to define access requirements and availab le repair and rehabilitation methods.
5. Repair/Rehabilitation Method • Select most effect ive repair or reha bililalion method .
RESPONSE TO DISCOVERING DEFECTS Reduce Pressure (P,l to safe lev el befo re re pair , plan p res su re red uc tions fo r repair:
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RESPONSE TO DISCOVERING DEFECTS 1. Redu ce Pressure to safe level before repair, ptan pressure redu ctions f or repair: • LEA KING PRODUCT: If pipe is severed or the defect is leaking, make pipe and surrounding safe . • REPAIR; Plan future pressure reductions depending on type of repai r/rehabilitation. • Some composite repairs require pressure reductio ns of 50%, • Recaating ma y requi re rem ova l of pipe from tren ch , and pre ssure may be required to be reduced to zer o. • Some regulations require pressure reduc tions is a pipeline is to be move d: e.q. regulat ions in USA require pressu re 10 be reduced to 50% of the MOP in a liquid pipeline, jf il is to be moved .
C_2006--.
7
RESPONSE TO DISCOVERING DEFECTS Reduce Pre s sure to s afe level b efore i n s p e c ti o n a n d repa ir: _ W e need to reduce pressure in a dam aged pipe because: . Pipeline damage can fail when held at constant pressure ('time dependent effects )
. Pipeline pressure i ~ ~~ve r constant, a n~ ,tan increase above the MOP, e.q. due 10 overpressures 'operational effects '
ALL DAMAGE
SEVERE DAMAGE If !he deled is very severe (e,g, very loog (wolh II " sk o f rupture). or very deep (>8O%w1), or II crack)
'80%' - For pipe wa ll def ects , low er operating pressure to 80% of tha t at
' 30% SMYS' - The pipel ine pressu re
which defect was discoveredanf hcted. until defect has been assessed. For stru ctural defects (e.g. buckling) structural assessments will be needed .
80% of the pres sure at which the
Pr essure should be controlle d.
shou ld be redu ced to the low er of defect was inflicted /disco vered . or a hoop stress level of 30% SMYS
Overpressures not allowed .
These stress levels can be waived if a risk analysis shows it 10 be safe to do so
C_
2O:I6 _ '
a
4
r: RESPONSE TO DISCOVERING DEFECTS - '8 0 % ' Pressure
• '80%'
p
-----
80%
---- -
p
The '80%' pressu re reduction is based Oil fu ll scale tests on defects (inc luding dents ) held at constant pressu re. Defects fail in line pipe due to plas tic flow. Thi s is time dependent
•
•
•
The part wall defects failed at higher 'hold' pressures than the dents.
You do not know the defect until you have inspected it.
• •
Therefore, it is reasonable and safe 10 assume you have a seve re defect (dent and go uge) . and hence you shou ld reduce pressure to 80% whi le you inspect and meas ure it.
Plus, you need some allowance for overpressures
Time <: p",,_
I ASME B31 8 requif9s00% 'oou ctlonfor ',""oha ni"" l dama ge
" 2000 Ro,""
9
RESPONSE TO DISCOVERING DEFECTS - '30% SMYS' •
Stress
'30% SMYS'
The '30% SMYS' reduction is based on the lea k/ru pture behaviour of defects. ,
cr
30% SMYS
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You have a low chance of a defect rupturing at stress levels of 30% SMYS or lower, This 30% SMYS limit applies to long detects You can relate a specific defect length to the failure (rupture) stress. This gives you your 'safe' operating stress. •
" P",,,,,," 2006 _ , ""
This 'safe' hoop stress must not be more that 80% of thai at which defect was c.scovcrocnnmcteo
10
5
RESPONSE TO DISCOVERING DEFECTS 2 . Est abli sh Critical Inf o rma t io n for eng ineeri ng assessment: • defect information : based on visual ..\ assessment, measurements and NOT. .".,- DefecUfailure history of the pipe line . • pipe and weld material : pipe materia l g rade . diameter, wall thickne ss , type of weld an d pipe specificatio n properties . • de sign and opera ti ng character istics : de sign spec ifica tion, design , current op erati on, cyclic and hydrates! pressur es, operating temperature , fluids , leakage rate, etc. • pipeline configuration : oerectrccauons . loca tion of adjacent welds , bends and fittings. curvature in pip e , ovalily of pipe . • consegu ences of failure: it oetect has not failed.
u
RESPONSE TO DISCOVERING DEFECTS • Remember... • We rarely assess a 'defect'
• We usually assess a 'defect report ' • Consequently, our defect assessmen t is dependent on the accuracy of the data in a defect report.
-__,_......
• Rubbish data... rubbi sh assessment!
tz
6
RESPONSE TO DISCOVERING DEFECTS •
Excavation will be necessary for onsho re pipelines.
EQUIPMENT NEEDED FOR REPAIR OF OFFSHORE PIPELINE: Example Concrete remova l mach ine
Remote ly operated veh icle (ROV) for inspection
Pipeline repai r method (from www.ocea nee ring.com)
7
- - - --
-
----- -
_ .
RESPONSE TO DISCOVERING DEFECTS •
Remember thai measurements in the field can have large errors
15
RESPONSE TO DISCOVERING DEFECTS 3. Carry out Defect Assessment: •
Urgency of the repair and analysis de pends upon: • defect seve rity: location, depth, length, orientation, and • fi nancial/strategic value of pipeline • th reat to environment and PR • regulatory/legal/insurance considerations • fai lure/furthe r failures consequences
•
Not all 'defects ' are pipe wall defects. Some will be structural anoma lies (e.q. buckles or unsupported spa ns) that will requ ire design/structural ana lysis .
•
Use engineering assessment - 'fitness for purpose ' - for repai r/no-repair decision .
" P " spa o 2[)(}1; Ro, 6i'
8
ENGINEERING CRITICAL ASSESSMENTS (ECAs) •
Establ ish any accepted defect assessmen t me thods with client and regu latory authority.
•
Establ ish 'level' of assessment: • Simple workmanship • Conse rvative 'cod e' calculation • Detailed 'fitness for purpose' assessment • Probabi listic assessment ('limit slate' ca lculation ) • Risk Assessment • Other - e.9 full sca le testin g.
•
Ensure defect assessmen t is cond ucted by experts , and a qua lity assured report is produ ced , with uncertai nties and conservattsms hig hlighted , and co nsequences of failure recog nised .
•
Always obtain three prices!
PROBLEMS WITH 'DEFECT ASSESSMENTS' • • •
• •
•
Usually very limited data to work on • this is the major co nside ration. Often high ly priced and naive (simplistic appr oach for co mplex problem ). Sta f cond ucting them are usually specialists without any engineering support, or knowledge of the specific pipeline , l.e . they will assess the defect, rather than the pipelin e. Usually 'distant' report , delivered to client with no 'ownership'. Usually the report does not add ress the client's ma in problem - how can I continue to operate my pipe line safely and cost effective ly for the whole design life? So lution? • Give a very clear and focu sed Scop e of Work. and do not ask solely for a 'defect assessme nt", and do not give any wide r work scope 10 speci alis ts without assurances. • Ensure that consu ltant works closely with you, and app reciates your pipelines, design s and operational prob lems .
D_2tU_·,
te
9
RESPONSE TO DISCOVERING DEFECTS 4. Location Assessment to define access requirements and available repair/rehabilitation methods : •
Platfo rm Topsides
•
Offshore Riser
•
Deeper Wa ter Depth Zon e ( > 50 m )
•
Inlermediale Waler Depth Zone ( 20 - 50 m )
•
Sh allow water Depth Zone ( < 20 m )
•
Inter-tidal zone
•
Inshore zone
• •
Onshore Valve Stat ions/Pigging lacilitiesITerminals
•
Road/River
., /
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SELECTING A REPAIR/REHABILITATION METHOD Repair Method ' Goating Repair
Grinding We ld Metal OecosncnFu ll Circumferentia l Sleeves Compos ite Reinforcement Sleeves Patch/Part Sleeve Repairs++ Mechani cal Clamps +++ Pipe Section or Pipeline Replacement External Coatings/Internal Liners • TM " """ "" -;>Udd..· ..... ,"ll,....
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- •• ""',.,,,. , """'
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''' ~ '''''''''_(
... AP111 60, 10<>0 " "'. "' ,.,.
_ ••_ _ ,. ".. , ,,. . _ .
'00' ... , . . . ' _
• There ere Olher methods of ropaifingJrehabiM3tlng, e g Upgrlldlng Ca thodic Protection. but onl y 'mechanical ' (ItId 'barner 'methods are cove red in this lectu re,
10
COATING REPAIR ' •
Pipeline reooating usu ally falls into one of two categori es: • repair coaling or • rehabilitation coaling.
•
Surface preparation is considered the most im portant stage of a recaating
•
Coating material should m eet NAC E Standard RP0169 T here are many different types of coat ing repair, and many product su ppliers
•
Some ar eas of a pipeli ne may require spec ial consideration , e.g. riser splash zones"
. . . _ . . ..._* - _ . ....__.._-_. . --...,...... !:'- _... .... _......., _ _ ... ... " _ _ >
_
,_",~_
...
__
Cooood_
,~
COATING REPAIR (cont.) •
A popul ar m ethod is tape , whi ch has a bitum inous rubber adhesi ve layer with either a PE or PVC backing . • This type of tape has a particular advantage in thai it will bond at the overlaps without primer activation . • Because of this feature it is supplied with a dispo sable paper inter1eaf layer to stop it completely sticking toge ther on the roll. • These tapes are made up to 1.65mm th ick. • The y woul d be very suitable for d aylwet co nditions and are made in temperate and trop ica l grades.
•
If the repaired areas could be prepared by abrasive blasting then it would be possible to use an epoxy repair coaling which would also be suitable for clay/wei conditions.
II
GRINDING Repair by hand filing or power grinding may be used if: •
stress concent ration at defect or impe rfectio n is removed, all dam aged or excessively hard material is removed, and the pressure carrying capacity of the pipe is not reduced.
•
API 5L allows grinding to shallow dep ths.
23
GRINDING (cont.) Criteria: •
ope rat ing pressu re level is reduced to 80% of recently demonstr ated hig hest operating pressu re.
•
limits of meta l remov al for non- inden ted defec ts can be sel by eng ineering cri tic al assessmen t (E CA), e.q A$ME B 31G limits .
•
grinding of indented defects is co mplex and not gen er ally recomme nded without significant pipelin e depressurisalion.
•
Use low powered too ls {e.q . <460 walls), or hand loo ls.
---~~--
C"",k"
12
WELD METAL DEPOSITION Ad vantages: • Sim ple and direct application of additional wall thick ness, but always use approved procedur e that is applica ble to your line/prod ucVdefect. • Gas Res earch Institute (USA) - We ld dep osition repairs are feasible to 900 psi for minimu m 0.125" wall thickness pipe . AP I 1160 limits this to >0.181" (4.5mm) . • Can be useful where sleev es are not pos sible - at fittings and bends - or wh ere acce ss is diffi cult. • Fatigue and fracture tests at Edison Welding Institute (USA) has sho wn good properties
25
WELD METAL DEPOSITION (Cont.) Co ncerns : • Red uce pressure (80% of discovery level) before welding • EGA can usually show it is not needed . • Possible blow-out o r penetration of pipe (burn-through): • pene tration depend s on wall thickness, weld heat input and removal of hea t by now of fluid inside pipe . • Possible loss of integrity of pipe following repair: • stanc strength and fatigue strength must be restored. • significant discontinuities must not be introduced . including hydrogen cracking in the HAl (heat affected zone). • can be diffICUlt to QA. • Can show as small pits in an MFl pig run , due to material change, and may lead to excava tion . 26
13
WELDED SLEEVE REPAIR (see API RP 1107 & API STD1104) Sleeve Seam we ld (detail below) Circumferential weld (Type B Sleeve only)
~,i ~t
I '"
,,
Pipeline
Back Ing Slnp and reloef
· ytlis ,s a very poPlltar,epa" methOd, ' Research @ AGA showed Ihese $Ieeves (Type B) can strenglhen pipe 10 100% SMYS . · Sleeve must reinforce d efedlve area, and restrain de/eel · Type A not recom mended for old ERW w£!ld repairs , W hen used to repair dents, hardenable material must be used to stop de nt moving under Shell
,-
PREFERRED We will no1 <:orISodoel 'ppO.in' s~ . e s these were used to reinJO
YSM 10 rep.ir buo kle s , leaki ng cla "l'S, etc
Tiley are cons 'oc r"';
l e~ary
FULL CIRCUMFERENTIAL WELDED SLEEVES S OF WE LDED SLEEVE • TYPE • T ype A - two half shells welded together to give 'clos e fit' • No pre ssu re containment ,
• T ype B - As T ype A, but also we lded to pipe (can be when line is in service) • Pressure co ntainment Stand-off Shell (when pipe is distorted or not straight) • Pressure T_ '.. ' SRJg-Flnlnv 51..._ WooI_I O I"Il*ino l containment (but not yet proven for leaking defects) Epoxy Foiled Sleeve • Used on Type A, can use on Type B - see later • Pre-stressed Sleeve - see T,.".. ' B' Snug.Fm ing $I . ._lV~ldo
• •
0_2OO!i""""
I
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za
14
FULL CIRCUMFERENTIAL TYPE A SLEEVE •
Type A - two half shells welded togethe r to give 'close fit', but no welding to pipe line. Works by restraint. • Th ese sleeves can increase fa ilure stresses >30%* of defective pipe.
• Reinforcement only • will not conta in pressure so no good for leaks or future leaks .
• MUST be close fit to restrain defect • Pressure reduction whi le installation will help . • Grind off weld reinfo rcements at DSAW we lds and girth w elds, bridge girth we lds. and use filler material at transit ion curvature o f seam we lds
' SeoW. ldlng Joc m. I. J u"" 1977 Row"'''' " ''''''' P'oe""" '",P;DOI,,,,,R ep;>.C, J F ~; e ' _.
.. _Coo..... NOl.. &
IPC' OO 2
Ca, M . ,ZOO2
FULL CIRCUMFERENTIAL TYPE A SLEEVE •
Wi ll not carry much stress if defect is short (length S (2001)°5)" .
•
Sleev e str ength and welds should be equa l to carrie r pipe if de fec t is long (length 2:(200t)05)... . .. .. Should extend at least 2" eith er side of de fect" Mite red sleeves not recommended '---~-
• • •
Note, we lding en ds is good practice to prevent cor rosion, or put heavy coating on, or sea ls in annulus).
•
Usually for external cor rosion on ly (dft ~ 0.8).
• •
Not to be used fo r circumferentia l defects. Best to fill defect or dented region with filler material to he lp good fit •
Hardenable ma te rials are epox ies . polyesters.
·S-W "' "'"\lJoL",o' , J,o. ' 977
••s.. Coo'" Not.. & 'R"""",,,,,,",,,,P",,,,,,. . ' o< P,,,," "0R.o"c J FK,.<,""
' ' '2'002, C.oo".
JO 2002
15
FULL CIRCUMFERENTIAL TYPE B WELDED SLEEVES •
Type B - welded to pipe •
Can restore damaged area so that failure
stre ss is ~ SMYS' of pipeline • Pressu re conta in ment. A nnulus ca n be press urised by dri lling using a ho i
la p. • Good to- leaking defec ts , or defects ma t m ay event ually leak. • Must have same pressure carryi ng capacity as carrier pipe. • Most operators ensure sleeve is sam e strength and thickness as damaged pipe • Shoul d ext end at least 2" either sid e of defect • Grind off wel d reinforcements at DSAW welds and girth we lds .
FULL CIRCUMFERENTIAL TYPE B WE LDED SLEEVES • Do not terminate the sleeve within 2" of a girth weld • Do not place two type B sleeve s closer together than one-half the carrier pipe diameter. • Can be used to repair most defects, includ ing circum ferential defects. • Easily detected by MFL sma rt pigs • Burnthroug h is av oided by ensuring good welding practices, low H2 electrodes , and a min. wall of 6.4mm (0 .25"). • Circumferent ial fillet welds can have delayed cracking if non-low H2 electrodes are used • Full penetration welds are used for the side seam.
a __
...,.;o;_.
32
16
WHY DO WELDED SLEEVE REPAIR 'WORK'? _ STRESS SHARI NG - If my welded sleeve fil s around the pipeline perfe ctly, I can achieve 'stress sharing' - my stress in m y carrier pipe is redu ced . _ If I tightl y fit my sleeve with a thickne ss simi lar to my car rier pipe , at a pressure of P r and increase the pipeline pressure of Po.
my sleeve shares the increases in stress from Po to P, _ Thicker sleeves take higher stress es. Any ca reles sness in fining will resul t in poor stress sharing
_ REST RA INT OF BULGING - Type A and non-pressu rised Type B sleeves stop a defect from 'bulging' in ductile hne pipe. Defects in pressurised pipe must bulge outw ards prior to failu re 33
FULL CIRCUMFERENTIAL TYPE B WELDED SLEEVES - SAFETY & PRESSURE REDUCTION • SAFETY • PRESSURE REDUCTION is alway s good practice, as we have repair crews around the pipeline. and the status of the defect for repair may be unknown .
• Repair pressure to operating pressure ratio of 0.67 has been recomme nded" • Some reports of hydrogen build up below sleeves , causing pipe collapse and safety concerns
t7
FULL CIRCUMFERENTIAL TYPE B WELDED SLEEVES - SAFETY & DRILLING • • •
DRILLING Sleeves ha ve bee n drilled in the past , due to the fear of a brittle fracture initialing under the sleeve and propa gating outside the sleeve" Note that if Type 8 sleeve is to be drilled (to remove hoop stress from damaged area) , the lop half of the repair sleeve needs to be fitted with a connection thaI can lake a sta ndard drilling ma chine and plugg ing device. • Drilling pipe shou ld only be co nsidered if defect being repaired is likely 10 rupt ure in futu re. • I.e will defect grow after repair (e.q . fatigue ), or will pipe pressure be raised (e .g pipeline to be uprated) • Current pract ice is moving away from drilling the pipe' " • Drilling can be difficult • Attachme nts 10 pipe sleeve can be dama ged • There is no evidence of a fracture ever extending from under a sleeve
0_2006_
.... J_OOId ..
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_ _....
~
O
_"'C:>0C2-21 ,n
~ d _ O ' - _ ,""
35
FULL CIRCUMFERENTIAL WELDED SLEEVES Stand-Off Shell
O P., ,,,,,,, =
_
6il
36
18
FULL CIRCUMFERENTIAL WELDED SLEEVES Stand-Off Shell . Stand off shell: . Used where snug-fitting sleeves cannot be used because of pipeline distortion or where the pipeline is not straight. _T his form of repair is far more complex in the installation process , as eac h repai r is made up in stages and can require many pieces.
37
FULL CIRCUMFERENTIAL EPOXY SLEEVES (EPOXY FILLED SLEEVE) • • • •
W ell-proven tec hnique, but uncertainties over long term integrity with leaking defects . No direct welding onto pipeline . Exp erience of use onshore, with non-leaking, defects . Sleeve fit up are problems minimised, as the gaps are filled by ep ox y • A large gap (' fit up') is tolerable (40mm)
• •
Cos t savi ng com pared to standard welded sleev es. Can be used where welded sleeve is imp ractical: • Bends • l eaks at fittings • Weakened girth we lds (good bond streng th)
•
Different systems available for use onshore and subsea: • longitudinal welded sleeve (as type A ) • sleeve with bolted fla nge 38
19
FULL CIRCUMFERENTIAL EPOXY SLEEVES (EPOXY FILLED SLEEVE) - schematic '
_
oe..-
p _
.......
_
~
",_"_~-,,,
""'
F
~-, ,.,---
"
39
FULL CIRCUMFERENTIAL EPOXY SLEEVES (EPOXY FI LLED SLEEVE)
20
WHY DO EPOXY·FILLED SLEEVES WORK? 2. DEFECT IS RESTRAINED
DE FECT REPA IR SHELL
1. LOAD IS TRA NSFERRED
EPOXY FILLING
PIPE LINE
"
FULL CIRCUMFERENTIAL EPOXY SLEEVES Effectiveness * • Full scale stat ic and cyclic** tests on sect ions of pipe con tain ing defects: • Dents (5-9% pipe diam eter deep ) combined with Defects (slots) (1217%wt deep ) • Defects (slots) (up to 85% wt deep and up to 457mm long) • Corrosion (60% wt , 457mm long)
• Showed the epoxy filled sleeve repair to have very high fai lure stresses • None of the 11 static tests on repaired defects fa iled . All surv ived >140% SMYS • Only one of the 10 fat igue tests failed (defect dep th = 60%wl, defect length = 457mm) - after 135,000 cycles at 124 N/mm2 • eu-, p ><00'< '"'. '-'" l ..... po,
R..... " "",om"'" ,.."_ _
•• , "'... ,....,.. u"'" • Oil, " ',
P',..;no Drioct . u SA
12. Nimm '
'"
, ~ ""
' PO"" ,... S<- .
~.".<. AC~
, C SymDO>O"'OO
10 ,.. .. """""" bel "," '~I"'~ I' ''' to ,O();)- '
'
,,"""""",." .. " ," '~"""" '''''''''"'''''' " l~ m _ ,.,""'''' 104M . . . . , "._""d"'"," .~.'m"';'1
42
2]
FULL CIRCUMFERENTIAL EPOXY SLEEVES· Effectiveness Failure stress! Yield " ' - -2
- - - -- -, = = = =;""] o Unrepaired
1.5 1 0.5
0 ,JAE!== 0.29 0.49 0.61 0.77 Defect (machined slot) depth/wall thickness
" ing' tests
.,e..-. P _.·,..._"' ........ ...""""". ....."._' _ _ R......·, N:;A" :t>r-...onc. _ . _ '_ _ us.o.
PRE·STRESSED SLEEVES· REINFORCEMENT (COMPRESSION) SLEEVE
•
This repair is two half shells fillet welded together, with an epoxy filler • Ca lculation s are co nducted to de termin e required 'stress redu cti on ' for the defective pipe, t.e. the she lls are go ing 10 be heated up , the n shrink to compress the defective pipe, and prevent defect pr opagation . .7 - --, • Pipe is sandblasted • Epo xy is app lied around pipe - acts as lubrica nt and subsequent load transferer • Sleeves are assembled • Sleeves are he at ed to specified tempe rat ure an d he ld in place by jac ks or cla m ps • Fillet we lds applied , no weld ing onto pipe, • Sleeves coo l. Sleeve 'co moresses'tbe pipeline. • Coat and backfill
'" B....-yoro.. " , ' T~, lookl u.. "' 0«><1 """""0'_ " -' 0',0>
C_
2006 R_1
& (in
_mOO , J" .... " , 001, P ""'"'
Installed (gritblasted )compression sleeve
44
22
PRE-STRESSED SLEEVES - REINFORCEMENT (COMPRESSION) SLEEVE • •
Popular and used in Cana da since 1994 Takes aboul1 hour to install (according to Petroline )
•
Up to a pipe len gth has been repa ired with end -to-e nd sleeves (en ds of individual sleeves don' t need to be butt welded together) Petro line says it has been used to repair sec , arc burns. den ting , cracks in ERW seam we lds. corros ion . mill defects Canadian code GSA Z662 accepts the re pair for corrosion
• Maximum sleeving achieved has been 24ft in 10 hour work day
• •
COMPOSITE REI NFORCEMENT SLEEVES Fibreglass re-infor ced comp osite material w rapped ar ound the pipe can restore pipe lin e stre ngth in hoop dire ction . No 'hot' work on line Usually defect is first filled with high comp ressive strength filler material
._.-r:
23
COMPOSITE REINFORCEMENT SLEEVES • Care should be exercised : • Not spec ifically designe d to resist bendi ng or axial stresse s • Som e wra ps do not a lter MFL indications. so cannot be detected by pigs • Technicians need to be trained to apply the repairs • composite strength and stiffness can diminish with lime
_ _der.v -. GE....
---~
COMPOSITE REINFORCEMENT SLEEVES
O_Z0CJ6lWv61,
"
24
WHY DO COMPOSITE REINFORCEMENT REPAIRS WORK ? DEFECT COMPOSITE WRAP
2. DEFECT IS RESTRAINED
~~S;~~~1.LOADIS TRANSFERRED
PIPELINE
0_""","_'
COMPOSITE REINFORCEMENT SLEEVES 'Clock Spring' • •
Polyester resin wrap reinfor ced by glass filament. Tightly wound and bonded to pipe . Wid th - 300mm
•
Typica l thickness 12.7 mm com prising 8 concentric layers. Two hours to com plete repa ir. Individual layers bonded using fast-curing ma terial with high com pressive stre ngth. Pipeline diameters: 4 56 On ly B" clearance is needed around pipeline.
Coil (laye r)
(t z-incnes).
•
• •
ft_
ft
• Ensure repair extends 2- beyond defect
50
25
COMPOSITE REINFORCEMENT SLEEVES-
'StrongBack' . 'Str ongB ack' - This product is a resinimpregnated . Kevtar reinforced , tape wrap, applied directly 10 the damaged pipeline . _ The wrap is water activated by im mersion or external application hence it can be used underwat er. • This method is usually used to reinforce small areas of corrosion and/or mechan ical damage
Remember: composote repairs must be inslalled
by qualJfied stall
COMPOSITE REINFORCEMENT SLEEVES 'Armor Plate' .'Armour Plate' Another pipe wrap repair method very similar to 'StrongSack' but the hardening agent uses a che mical rather than water. • Each wrap is 12.5" wide . This method is usually used to reinforce small area s of corrosion and/or mechanical damage
I
Remember: some composite detected by pigs
~its may not be
I
26
COMPOSITE REINFORCEMENT SLEEVES 'Pe rm a W ra p' .Perm aWrap (Wrapmaster) _4· 36- diameter _ W idths of 6" up to 18" _ 2 man, 45 minute installation _ All contain metal strip for detection by pig
•
Remem be r: pressure reduct ion s may be reQuired for composite repairs.
COMPOSITE WRAP REPAIRS Mechanical damage a c omcosue wraps have been evaluated for repairi ng mech anical damage' e 'Ihere is some debate about the usefuln ess of wrap repair s for mecha nical damage or cracks in pipelines ' " e uqoto lines can be heavily pressure cycled (fatigue). • Durinq pressu re cycling, the wrap material can allow movement of e.g . denied regions , and this lack of const raint may lead to fatigue failures in lines that are pressure cycled . a c onsequenuv jf the damage is not ground out unde r a wrap repair. ther e ma y be a failu re risk
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_ _ -.....:w.".""._ "'J_ _ .. _
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_
r _
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_ _ ._ _•
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_
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27
PATCH REPAIR ' •
A simple quick repair. but only gives limi ted support 10 defective area
Fille\ W eid
• But requires live welding
•
Usually circular patch made from same material as pipeline .
•
Axi ally orientate d fillet welds m ay be prone 10 fatigue dam age. We call also hav e a 'hatl sole ' repair; lhis is where we we ld a
half shell to the
pipe~ne.
and fillet weld it to the line pipe.
55
WELDED PATCH/PART SLEEVE •
Pat ch repairs are now only us ed on: • low stres sed pipelines • low SMYS line pipe ( ~4 0 . 00 0Ibflin2 )*
• non-teakinq defects, or co rrosion that is leaking
'''''''DOT
"~CHI_'92""M _'<12111
2X
HOT TAP REPAIR OF DEFECTS - Direct removal of defects
• Defects such as mechan ical damage, can be removed by hot tapping the defecti ve area, and cutting out the defect , or cutting out the section of pipe • All the defective area must be removed B VPASS
1-:-\- -
-
-
-
-
'IE
-3-
DEFECTIVE
PURGE r '"' ree
~--r+'c----,-UJ-)-.~ . _"-:-l--. BYPASS
S TOPP ~E
'"
'"
SECTIO N
=:1
PERMANENT REPAIR METHODS· API 1160 GUIDELINES We ld Repair" External Detect - (S80%wt)Y Internal Def ect- (S80%wt) N Externa l Detect- (>80%wt) Y' Internal Defects (>80%wt) N Leaks N
Type A Type B
ccrnpcelte!
Hot tap
steeve! Sleeve y y
Y
Y'
N
Y
N
Y'
N
Y
N
Y
N N
Y' Y'
N
Y
N
N
Cracks
N
N
Y
N
N"
Girth We ld Defects Denis Denis with detects "
N N N
N
Y
N
N
Y'
Y
y4 ,3
y3
N' N
Y'
Y'
YOCA ,W 'YS"HD A'''",''U~
WALLTOWE cDONTO_ Cl.PPtICA-lO" TO " 0 ' ' ' -, """ I e 'S Gr ~r l""- l y , '''' '' ... ' HOD TO <,"""w' DEFECT DEP'HS 'NDCS""'Y PRAe- ICE I ~ " AMERICA IS TO LIMIT riPE A SLEEVES A~D CO"POS RWA'.' fO NOT EXCEED,"O"",,,WT
1"1'"
'N
A"V
lJA>MC' "
o""'."p"""....
1" ' ",," "uST HA'J< "'!oN REMO""O, ' .G. BY GR,'
re
"' ''';'$
eo.. m, ~ '" ,,.,, w "," """",,' "
D,,,),.. """"'loo m",,.~
Se EEVE " "S- " ' FILLEDW TH·' CO" PRESSl8 cE ""TERIAl " r''IOTO ,AWEcD CRACKS Te ATARE ..aT l",,"'NC CA, BE HOTT"""" D TO REMOVEC.....C" SOME COMPGSITE REPAIRS CJ.N . . u SED ON ST.....,C HT P PE W TH O,"TS. IF T1
29
MECHANICAL CLAMPS
sa
MECHANICAL CLAMPS • Pressure containing clamp , with seals at eac h end • Eiastomenc seal will co ntain leak - but the Seals ends are sometim es also welded as back up for the sea l • Thick and heavy, due to large bolts needs to ensure adequate clamping forces • Simple to install , but heavy 10handle. • Designed to conta in a leak . If defect may result in a rupture, leak clamps are not recommended. • If pipe is leaking, an offt ake will be fitted to the lop half of the clamp to route product away , and remov e build up of pressure in clamp du ring repair.
30
MECHANICAL CLAMPS • Mechanical clamps are usually considered as 'temporary' repairs. • However specialised subsea clam ps are often not replaced and become a perman ent repair subject to regular inspection.
• Several types of clamp : • Pudco. PII Tecnomarine , HydroTech, Furmanite. etc r,--
" eals
'Plid co' clamp 61
MECHANICAL CLAMPS
200 1 - Ala!.ka _ Jet Fuel Leak - Corrosion pols
O_2OOlI R..6i l
31
MECHANICAL CLAMPS - Underwater Underwater clamps are similar to onshore pipeline cla mps,
_._.-"'..--..-..--_-._-
63
MECHANICAL CLAMPS - Underwater Underwater clamp s are
simi lar to onshore pipeline clamps . but they wi ll need diver or ROV support. and vessel
support
32
MECHANICAL CLAMPS - leak repa ir offshore a The repair of a pin-hole leak is relatively elementary as compared to a spool piece replacement. _ In simple terms , for the pin-hole repair. soil/overburden must be cleared and the concrete/corrosion coa ting removed for a leng th of 40" to 60". _ A repair clamp can then be lowered into position over the pipe and set (activated). aT hese operatio ns can be done by divers a ln deepwater (>1000ft?) - these operations are all performed by ROV s. a Oiverless repair clam ps have been manufactu red and tested in sizes to 18" . They are owned by pipeline ope rato rs and remain in inventory as an emergency, stand-by repair capability.
MECHANICAL CLAMPS - leaking fittings
'Enclosure' type repair compone nts are capabl e of repairing/sealing damaged flanges and 0 bends/elbows in both on and offsho re lines.
"T R • ...".,..,.'I3I ..... .
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_ G _,...· ... _ _ .......
_........,._OOh>o . . .
-..... Of._ ..
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66
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33
PIPE SECTION REPLACEMENT
PIPE SECTION REPLACEMENT Cui out defectiv e pipe and replace by pre-tested section, by: •
Isolation of flow and pressure , dep ressu rtsatio n and purg ing of section 10 be rep laced ,
•
Hot-tap, Stopple and Bypass to bypa ss flow and keep pipeline operating, perhaps at a reduced pressure .
j
Remove
)
< ",x.
)
Replacement section may be installed by: • •
We lding - preferred Mechanical Con nectors - popular offshore
0_200II_"
68
34
ISOLATION METHODS Isolate a section of pipeline for replacement by: •
Valves
- Existing valves within the sys tem
•
Conventional Pipe Plugs
- St opper s set by Hand
•
Isolation Pig s/Sp heres
- High friction. driven to location
•
Rem ote Setting Plugs/Spheres - Set by um bilical or remotely
• Pipe Freezing Plug • Hot Tap & St opple
- Freezing of a plug of water or gel - Allowing flow to continue in bypa ss
• Mechan ica l Tees • W elded Tees
Isolate
Plug/valve/pig Remo ve
ISOLATION METHODS· PIPELINE STOPPERS AND ISOLATION PIGS
•
Pipelin e Stoppers - set man ually and generally used as seco ndary barrie r (low diffe renti al pressure - up to 20 barg): • Pronal Plugs • available wil h pressure control. purge and vent facilities
• Hyperbaric welding bladders
•
Is olati on Pig s/Sph eres - driven into position (lOW differential pressure up to 5 ba rg) • • • •
Sealing Pigs Balching Pigs Spheres Gel Pigs 70
35
ISOLATION METHODS PIPE FREEZING PLUG Air compressor
Liqu id Nitrogen
with dryer
dry air 10 coola nt pumps
Freeze
exchanger and p ump
.>
Instrumen t recordin g pa nel
Freeze J acket
_ _ ; 'c.-
.
, ~
.
,
"
HOT TAP, STOPPLE AND BYPASS Bypass fitting ,...stoPPle mli ng 1. WE LDI NG - The fou r fittings ~e permanently <, sec ured (welded) 10 the line. !> ~ G:!J , 2 . Temporary Sandwich Valves are installed on the fill ings , and taps are made thro ugh all the va lves, Tapping The ta pping mach ine s have cutte rs tha t remove a~~e:!" ::=lmachine cou pon of the pipe wall and remove the co upon fro m '\ _ the line Sandwich 3. Two stopple plugging machines are installed. valves Product is diverted through the temporary bypass. _ Stopple The isola ted section is purged. Mod ificati ons are ~_~Ugging _ mach ine ma de 10 the isolate d pipe section . The ne w section is ~ ." purged and equalized , and t he plugging heads are retracted 4 . The temporary bypa ss is removed . Plugs a re installed in the stopp le fittings with a lapping mach ine . All equ ipm ent is then removed and blind flanges are installed on the fitti ngs to complete the Tal<"" from lt>ol TO W _ _ _ te
L
- '
....
job . e _1OOlI ....0Y.
n-os_ a dou ble
~_~t
n
36
HOT TAP, STOPPLE AND BYPASS •
HOT TAP: cutting into a live pipeline using a special tee, welded or clamped to the pipeline.
•
STOPPLE*: insertion of a tem porary plug into the line , through a hottap tee, to isolate a section of the pipeline.
•
BYPASS: attachment of bypass pipe to a pair of hoi-tap tees to provide a flow bypass
If
ill]il ""', ·'''~l · ~-----------"' '~l~' ~':-i'-~-'~-'-~ STOPPI.E
BY PASS
aroun d
VAlVE
'T
]T
PURGE
feo,
f- - -E~~E Et:L "]- =--==j TEE
STOPPLE
ree
'Stopple' means stopping-off P
HOT TAP, STOPPLE AND BYPASS: Onshore
37
MECHANICAL CONNECTORS Subsea Pipeline Repa ir •
rep lacement spoolplece
•
replace section of line at a riser or mid-line
Con nec tors used in conj unc tion with •
Misali gnm ent ball flanges ( MAF )
•
'Pup' piece for axial adjustment
•
Standard RT J (ring-type-joint) flanges
•
Swivel Ring Flanges
VENDORS: Ceani c Corporation ( Big Inch ), Cooper Cam eron , HydoTech Systems (Oil States ), PII Tecnomarine, Hydra-Tig hl , Oil Stales Industries ( Mer1in conn ecto r)
REPAIR COST COMPARISON (late 19905) REPAI R METHOD
CO ST (US$)
COST INDEX
Clockspring
4650
1
Epoxy Sleeve
5800
1.3
Hot tap & stopple
>100,000
>20
Plidco clamp
16200
3.5
Snug Sleeve
7200
1.6
Stand off sleeve
8950
1.9
24" hne 'n UK. not iocIud ,ng C/VIls works a nd eXC3yabon costs . Repalr oI SOmm brig corrosIon T. .... _ .. ""'...... _ ........ _ 001 ..... ..., _ ....... """'T
D .....
~~""'--"p,
'-"- '..
_ :/OOOI_ '
38
REPAIR - GENERAL GUIDELINES
REPAIR· EXAMPLE OF DECISION TREE Conclusion from defect assessment:
Repair methods: ~.
Surface defect/stress raiser
Reinforcement required
Leak to be sealed $~X~Ie damage
to be replaced
-
Grind defec t
· ·•
Type 'A' welded sleeve Epoxy sleeve Composite sleeve
· · · ·
Type ' B" welded sleeve Mechanical sleeve Sland-offShcll Replace pipe sectio n
39
REPAIR GUIDELINES (e.g. AGA Catalog No L51716)
.
,
l .ak (throu gh .. , II dol.... 1) Lea k unde, pr. nur. bl.rnll Corroalon
" ··
De e p IXI.,n, 1corrOllon >0.81 Int ern al Co rr oal on
O.nt Dent. goulle Sh. llow Crack" 0 .4 t Deep C..ck > 0.4 \ Sum Weld Defec t
'CO Wrinkle or IoClII b uck le G irth w eld delect
..................
_.
~
~
~
-•• ·,• ·· • •·
¥!. , ~
·· -• ·• •· • -•··
.. - ,.I. h s e
·· -• ·• ,· • ·· ··
",1? Rli ~-g Q
'"
, 0
~~ d
• l
•
., · 0
h , ••
·- -· -·· -- -· --• • • • - - - - • •
-< < <
• •
• < <
• < <
-- -• ·· • - •
• •
·· ··
<
<
< <
<
, ,
· ·•
< <
•, • <
(See also . ASM E B31.8S-2oo 1 and API 1160 for more up to dale guidelines) (Note - These guide·lIne s do not always agree ....ih each other)
RESPONSE T I M ES FOR DEFECTS IN API 1160Liqu id Lines REPORT' IN 30 DAYS & REPAIR IN 30 DAYS'
REPORT AND MITIGATE IN 6 MONTHS
DEFE CTS >80% wt
- DEFECTS >50% wt w it h w idespread c trc exte nt, or at foreign lin e cross ings ·GOUGE/GROOVE >12.5% wt
DEFEC T HA S FAILURE PRESSURE <
MOP TOP OF THE LINE (4·8 o 'c loc k) DENTS WITH DEFECTS
OTHERS CONSIDERED SERIOUS BY OPERATOR
0 """""", 2006 _
'"
DEFECT HAS FA ILURE PRESSURE < safe operatin g pressu re (as determ ined by (e.g.) ASM E B31G • DENTS >6%od • DENT S ON WELDS OR WITH DEFECTS
• IDENTIFIED CRACKS • WELD DEFECTS >50% WT ·PREFERENTIAL WELD CORROSION
1 - Temp. mitigation is required within 5 days of receipt of report 2 - e.g. from pig vendor
80
40
RESPONSE TIMES FOR DEFECTS IN ASME 831.85 - Gas Lines (Defects detected by pigs) IMMEDIATE RESPONSE (defect on point of failure )
SCHEDULED RESPONSE (defect is significant but not on point of failure
MONITORED
'Promptly' re vie w after defect is discovered or reported
Review within 6 months
Revi ew within 6 months
- Any me tatrcs s t hat wo uld leak to near -term leak or rup ture
Corrosion w it h failure pres su re>1. 1MAQP
- Corrosio n w ith fail ure pressure<1.1MAO P··
- Dents on w eld s wi t h deplh>2 '!.OO "
-Metal los s in/around DC or I F
• Mecha nical damage" • Den t w ith d epth >6 %00 " - Den t w ith cr ack' • Den t on n on -d u ct ile we ld ' o See also A SME B3 1.8 (8 51.4)
ER WIFW seams Examine within 5 days of re view Repair/remedialion 'promptly'
(defect w ill not fail before next inspection)
se c , Dent wit h gouge Examine and evaluate within 5 days
at
' For lines ~30%SMYS. " Using ASME 831G or equivalent
RESPONSE TIMES FOR DEFECTS IN FINAL RULE 195.452 Feb 2002) - Liquid Lines EVALUATE & REPAIR
IMMEDIATE REPAIR
-Defect has predicted BURST pressure 80% wt -Dents on top of line
(e-e o'ciockj with dep th >6% nom . pipe diam eter -Dents on top of line (4-8 o 'cloc k) cont aini ng any defe ct -Any other defect cons idered serious
~
P""","" 2006 Rov,,! '
',""",,,vo<}
",",,,"
Within 60 days of discovery
Within 180 days of discovery
-Ali dents on top of pipel ine with deplh >3% pi pe diameter (or >0,25" for NPS of < 12") -Dent in bottom of pipe with an y stress raiser, crac k or me tal loss
-Defect has predict ed (e.g , by RSTRENG ) 'o perating ' pre ssure 2% pipe diameter (or 0 ,25" for NPS less Iha n 12") cont aining a weld -Dents > 2% pi pe diameter (o r 0 25" forN PS less th an 12") at lop (4"8 o'c lock)of pipe "Dents at bott om of pipe of depl h > 6% pipe diameter -Corroson > 50% nomi nal wt , -c orrosio n of, o r along. a longitud inal seam weld ·M et al loss > 50% @ pipeline crossings, with widespread circum ferential extent, o r at girth we ld "Possible Crack , lh al is confirmed by excavations "Go uges/groov e > 12.5% nom inal wt
'00"",
"'" " vo ....
....... """',,"'" ,nt""".Iion"
82
41
RESPONSE TIMES FOR DEFECTS IN FINAL RULE 1 9 2 .9 3 3. Dec 2003) - Gas Lines REPAIR
IMMEDIATE
W ITHIN ONE
NO LIMIT (but mus t reco rd and monitor)
YEAR -Delec t has predi cted
-Dents wit h a
-Dents on bottom of line (4-8 o'clock) 'Mlh depth >6%
BURST pressure
dep th grea te r than 2% pipe
nom. pipe diameter'
=<1 .1x MAOP (e g . us ing ASME 63 10 or R$ TR ENG } - A dent with any meta r loss , crack or stress raiser.
-Any other defect considered serious
diameter" affec ting a g irth or longitudi nal seam weld
-Dents on top of line (4-8 o'clock)
- Dents on top of line (4~8 o'clock) wit h de pth >6 % nom . pipe diam eter ' shown by analys is to hav e low
strains -neets wit h a de pth gre ater than 2% pi pe diameter"
affecting a girth or longitudinal seam weld shown by analysis \0 have low strains, plus consideration of weld quality
with de pth >6%
nom, pipe diam ete r"
·_ .....,05·_ ....
0 __-.
-~
_P
.... O:/"i· ... _ P o o
_ .....,'T
i>'''S) .. (JtP'$) .. ... .... ' T
83
CONCLUSIONS •
Ga ther all data rela ting to defects & pipeline
•
Co nduct defect assessm ent s. • If repair/r ehabi litation needed .. .
•
Cond uct cos t appraisal.
•
Se lect most suitable repair or rehab ilitation solution .
•
All repa ir m ethods ava ilab le has a role • Choose the repair me thod tha t best suits the defect and the pipelin e .
•
And finally... fully document & reco rd the repa ir.
42
ADDITIONAL INFORMATION
85
'APPROVED' REPAIR METHODS
• Note that some suppliers of repair methods may 'claim' that their repair has been 'approved ' by the USA Department of Transportation • The DOT does not approve repa ir equ ipmenUmethods • Repa irs either meet or do not meet standards. • e.g. You can say that line pipe meets API 5L standards. but you cannot say that API 5L line pipe is approved by
DOT • Some concern over non-American products in USA. • For examp le, ISO or European standards and spec ifications will not automatically be accepted in U SA 85
43
THE FOUR STAGES OF REPAIR AND REHABI LITATION
STAGE 1 lnspectoooJOe1ectlon
PROJECT MANAGEMENT
STAG E 3 Assess ment 01 Defects
~ ~
STAGE 4 Repa"IRehab< litil te
0 _200& _ _,
"
REPAIR AND REHABILITATION DRIVERS AND APPROACH •
DRIV ERS · Many re pair o r re hab il itatio n projects are not driven by the choice of
repair o r rehab il itatio n m et hod. Th ey are d riven by economics , urg en cy or
engineering co nsiderat ions . •
•
COS T· For example, the cost of the repair clamp for a damaged offsho re pipeline is negligible compare d to the co st of the vesse l tha t has to be hired to install the repair. Further example: it may be cost benefici al to replac e, rather than rehabilita te , a pipel ine a new, larger. more efficient pipeline can give lower whole life costs than an age ing , small , inefficient line, albeit rehabilita ted. URGE NCY - A catastrophic failure (peop le or environmental) has such a devastating effect on PRo etc" that the least 01a compan y's wo rries is the type of repai r/rehabilitation. Cost to public image, lost revenu e and dean up costs are key considerations.
•
ENGINEERING · The 'engineering' associated with any wOO on a pipeline may be the cru cial cons iderat ion. For example. an offshore line that has lost its coat ing. and is floati ng, an onshore line that is to be lifted out of a trench and recoated 'live' (while pressurised ).
•
APPROACH · Pipeli ne rehabilitat ion is similar to pipeline construction section rehabilit ation, backfill, inspection, etc.] , and re qu ires th e same eng ineeri n g approach,
u.e. retri eval /trenching ,
88
44
REPAIR AND REHABILITATION· COST MODEL Repair or rehabilitation is usually driven by cost or urgency Cos t
Fa ilure Probability , (Pr)
target probab ility
f[Optlm um P,
,, j
p,
Time
89
REPAIR AND REHABILITATION· COST COMPARED TO REPLACEMENT
6-14 inch
perce nt of new construction 70 -130%
16 - 24 inch
50 - 90%
28 - 48 inch
25 - 50%
pipe size
a r hese costs are for landlines. a s meuer diame ter pipe is che ap to buy, hence mater ial costs of a new pipe line are low_ _ Rehabilitation becomes mo re cost-effective as the diam eter increases, _Note : som etimes the people and dis ruption problems associated with new const ructions (e.g . re-Iaying a pipeline in an env ironmenta lly sensitive a rea, with associated problems with pub lic image and lengthy negotiations) may mean an operator chooses reeaaling/lining, even when the capita l cost for new const ruction is lower.
C Po"" ,,,," 2006 Ro'6I1
90
45
REPAIR AND REHABILITATION COST BENEFIT 80
70
160 km lo ng, 914 mm dia m eter l and pipeline
~~-
"ro 60 g;.. 50
~
40
g
30
o
~ 20
10 New Line Coating repair Hydro & Repair
III & Repair
91
Il>P ",,,,,,,, 2000 Ro v 6i '
REPAIR AND REHABILITATION OVERALL STRATEGY
I
DEf iN E REPAIR/REHABILITATION AND MONITORiNG STRATEG Y
Build up data bas e
Asses s li kely
repair/rehab. meth ods for each locat ion
..1 Pr e-in ve st in to o ls for rep air /r ehab. Set up standby repai r/ rehab. tool sto rage facili ty
··h
of p ipe line technical
Set up res p on se te em and re pair/rehab. co-ordinat ion
data a nd
team
repa ir /rehab . da ta
......, Write repair/re hab. manu al and
Def ine d ef ect assess ment
a pp roa c h a nd criteri a lor each
Pr e-q ual ify co nt ract ors to repa ir o r rehab subse a an d o n shore p ipe lines
I
I
pipeline
Define environmental and hazard res po nse
proced ures W r ite repa ir/re hab . s pec ifications
I Ensure access to pipel in e along ro ut e
I
I
Define con d iti on m o nito rin g strategy
I
wnte
respo nse plan
I
I
Appoin t inspectio n contractor
46
REPAIR AND REHABILITATION· PROJECT MANAGEMENT •
The project management princip les used on new pipelines should be applied to pipeline rehabilitation: • • • • •
•
Project Concept (Goa l Statemen t) Project Study and Definit ion (Plan of Execution) Pre-Construct ion (Award Contract) Co nstruction Ongoi ng operat ions (Inspection and ma inten ance)
Project management will co-o rdinate many diffe rent services, including inspections, protection survey, coatin gs select ion , etc .. Prob lems may include: • sco pe of projec t difficu lt to define as many uncertainties exist (e.q. location of • • • •
cor rosion) deali ng with older pipeline, whose design, drawings, etc" may be difficult to locate/prove project s are often 'fast- tracked ' due to ope rationa l pressu res Project is often on a pressurised pipeline with additiona l safe ty risks lake up and remova l of existing coating may be disposal problem
• etc.!
93
REPAIR AND REHABILITATION ACTIONS
I
DAMAGEID ETERIORATION REPOR TED
I
Reduc e pressu re?
I
I
Collect data
I
Defe ct Assessm ent, defi ne repair or r ehab. req u ire me nts Recommended repair/rehab . methods
Refoa~~~~~ab. sta ndby
I
..oj. ······f··········_·
.
..1
I
~
Assess location of damage, define access requi rements
Select repairlre hab . m ethod Carry out repa ir/rehab., ins pectio n and rein statement
Mobilize co-ordination and planning team Decide action to limit environmental damage & hazards Organize access and consents Mobilizetask force for repair/rehab & damage limitation
47
REPAIR AND REHABILITATION - ACTIVITIES PRELIM INARY ST RATEGIC POSITI ON 1 Damage location , excavation and marking 2 Preliminary damage survey 3 Exposure and stabilization of damage site 4 Coating removal/pipe cleaning 5 Detailed inspection of damage 6 Damage assessment & reporting FINAL STRATEGI C DECISIONS/C OST MOD ELLI NG 7 Repair/rehabilitation method decision 8 Equipment fabrication and procurement 9 Repair/rehabilitation procedure pre-qualification tests 10 Repair/rehabilitation damage 11 Inspection and documentation 12 Site reinstatemenUprotection
THE COST OF REPAIR AND REHABILITATION • About 25% of a pipeline company's maintenance budget is taken up with repair, replacement and rehabi litation; .50% of this is spent on inspection and mo nito ring, 30% on compressors, control equipment, etc .. • This will be equivalent to about $400/km .
'Repair' - small scale remedia tion (e.g. repair defect) 'Rehabilitation' - large sca le remed iation (e.g. recoat)
96
48
WELDED SLEEVES - SOME WELDING GUIDANCE
AVOIDING BURNTHROUGH _ Early work showed that burnthroug h is unlike ly, if you use low hydrogen electrodes and the temperature beneath the we lding arc is <1800F(982C). _ WA LL THICK NESS - This tempera ture is unlikely in wa ilihicknesses >;; 0.25" ~6.4mm) , using norma l wel ding procedures _ Welding onto th inner wall is possi ble with special, co ntro lled procedures (e.g. low heat input) _N ote thai interna l press ure (hoop stress) and level of product flow are perceived as important (som e companies reduce pressure and ensu re a flow rate), bu t work at Battelle and EWI show them to have low importance. • PRESSURE (stress level) has little effect, as the size of heated area is smal l, and the hoop stress can easily redistribute itself arou nd the sma ll area (as it does around a pit). Actua lly. high stress may be beneficial: provi ded we have a flow rate, at high pressu re the risk of burn through is lower, as the thermal cond uctivi ty of gas is higher at high pressu res ' _ Note that a pressu re reduct ion ma y be necessary to reduce risk of any defect fai lure during inspection and rep air _ FLOW RATES - Maintaining flow doe s keep temperatures low er, but the therma l mass of pipe and contents are more important, and they are usua lly below 982C eve n at low/no flow rate' _ There are programs avai lab le for calculati ng heat flow and the risk of burnthrough - contact Batt elle, USA, or EWI , USA _
• FlOW
W E"""", H o, ." o!lo- se " ,"" ~".' I""'" ' ""'" ' g' f'po-"o""''''W ''!J """"'e
""e, mOl "" <"tlco' '''''' "' '" wal'od « 6 ' ''' ''' II',," " ,.
98
49
AVOIDING HYDOGEN CRACKING _ As we are welding onto a pipeline with flow. the welds may coo l ve ry quickly. _ This accelerated cooling can lead to hydrogen crack ing, as the flowing product removes heal from the pipewall _ Hydrogen cracking requires thre e conditio ns: • Hydrogen in the weld _ Susceptible weld microstructure a 'Iensile stress acting on the weld _ To avoid hydrogen cracking , we must prevent one of these three conditions _ We will inevitably have som e residual stresses in a weld. therefo re the primary method of preventing hydrogen cracking. is to use low hydrogen electrodes or low hydorgen processes . _ If we cannot use low hydrogen electrodes/processes , we can : _ Specify minimum required heat jnputlevet _ Specify a temper bead deposition sequence _ Specify a minimum req uired preheat tem peratu re _ A combination of the above three s... W 8 """"
"' _
' of " .......,"" ..".." .. .... _~ .... .
p,,,.,,.... ..... P9O""ll
.od '_ ', eo,.,l.........,.,_ .."" . F•• ;/001
UNDERWATER REPAIRS
C_
:ll;
100
50
HOT TAP - hyperbaric ' welding underwater
.
,
~
.
_ Subsea hyperbaric welding is widely used for joining offshore oil and gas pipe lines and for underwater repairs to produ ction platforms. _ The welding is done by Divers or equipment installed by Divers in a dry "habitat" which is sealed onto the pipeline and filled with a breathable mixture of helium and oxygen, at or slightly above the ambient pressure at wh ich the welding is to take place . _ The divers often prepare the equipment and the actual weld ing can be controlled from the surfa ce by the mother ship . _ The area under the floor of the Habitat is open to water. _ Thus the welding is done in the dry but at the hydros tatic pressure of the sea water surrounding the Habita t. _ _ GIIILO ... _ - - .
'"
PIPE SECTION REPLACEMENT - deepwater offshore _ SpOOl piece replacement is a more comp lex repair requiring a much larger scope of details in deepwater . There are two basic scena rios for a replacement, which are as fol lows: _R etriev e Pip eline Ends : One scenario is to cut th e damaged section from the pipe line , retrieve both ends to the surface , we ld repair fitting s onto the ends , lower the ends to the sea floor, and insta ll a spoo l piece, us ing Hydrotech Grip & Seal a re mote connector system. _Repair o n Botto m : Using this repair scenari o , the pipeline would also be cut on the sea floo r, the damaged section removed from the immedi ate loc atio n, and the pipeli ne ends prepared (coali ng rem oval, etc.). a r nen mecha nica l connectors, including connectors for mating with the replacement spoo l piece , would be slipped over the pipeline ends. • Based on measur ements made subsea by ROV. a spool piece wou ld be fab ricated on the surface and lowere d to the sea floor . • An ROV would activate the spool piece connectors and make the final lie -in .
'"
51
PIPE SECTION REPLACEMENT - deepwater offshore [1 1 ' - _ ' - " H ' - ' ' ' '_ T»o US _ ....--s.-.__
...... --".. . , 1- ·- .).. _
10" '_113 2111. _ _ 1
~
....
~
_ """,'-"10...,...,.
..,.,..,..,ceI _ _ f._
_.
' 3_<::t _",,,,,,GJ'ol
",. .>
go,
, _' .. _
(~')
"''''''''''"'. . . ~'''
''''
INTERNAL LINING
C P....- 2OOlI_'
""
52
INTERNAL LINING •
Pipeline is fitted with an internal liner to prevent furt her internal corrosion; however the system has limitations: • pipeline has to be laken out of service and cle aned • liner ca n onry be in stalled in short lengths (typica lly 800m ) • ends of the line r ha ve to be seareo qoined to next section
• concerns over use on sour service pipelines
•
The re are many possible system s at present , e.q.: • Cur ed in- place - a th in rein for ced text ile lin er, fixed by adhesive • Modified slip lining - polyethylene liner com presse d and exp anded • u -Procese- polye thyl en e deformed to U shape. roll ed in and expanded
• High Density Polyethyl ene - installation method not established
105
HDPE LINING "SWAGELINING"
WWW_$wagelin'llQ.COlTl
53
INTERNAL PAINTING
• Pipeline is painted internally to prevent future corrosion. • Approximately 30 km can be done in one go. • Rigorous cleaning (mecha nical and chemical) required. • Batch of paint pushed through by pigs • Paint applied by robot • Cost - 30% of new pipeline construction.
OP...._
2005_'
INTERNAL PAINTING
www.crc-evens.cc m
'08
54
EXTERNAL COATINGS FOR ONSHORE PIPELINES
109
EXTERNAL COATINGS FOR ONSHORE PIPELINES •
'Field' coatings will not be as good as 'factory' app lied coatings: • Faclory coatings: • coat tar enamel (long and successful reco rd, and ca n operate up to BOC, but now some hea lth haza rds identi fied ). • asphalt enamel (co nsiderable track record , applied in similar man ner to coa l ta r, but no iden tified health haza rds) . • Coa llar & asphalt are soft mat erials and require careful handling and usually sand padd ing/g raded backfill , and care when field ben ding (high strains - up to 4 %.). • fusion bonded epo xy (can w ithst and higher temps (70- 100C). Res ists di rect impacts , and is good for field bendi ng). • mu lti layer polyo le fin (polyethylene (PEl doesn't bond to stee l, so multi layer needed (e.q. fusion bonded pnm er/co-polymer adhesiveJPE outer layer. • Re sistant to dam age . and the need for sand padd ing decreases). _
'.!lEc-.,'
"""
,,,
55
EXTERNAL COATINGS FOR ONSHORE PIPELINES (cant.) • 'Field' coatings will not be as good as 'factory' applied coatings: • Fie ld applied coatings will be lower quality than fact ory coatings: • Surface preparation - is the most important aspect of coaling. • blast cleaning (manuall1ine travel ) by steel shot or sand . • Coaling removal - mechani cal bealing, mech anised scrap ing , high pressure water jets. • Water jetti ng is extensively used , and can remo ve coa ling (out of ditch) on a 24 in. pipeline at a rate of - 3 m/min. • In situ rates are lowe r because of ext ra care required with handling of the pipeline. • Coati ng - Line travel machines can be used . but they can on ly apply liquid based coat ings • Cold appl ied bituminous wrap may be used . but it is eas ily damaged by stones, etc.
_------
...
REFURBISHING ONSHORE LINES _ RECOAT ING - American Gas A ssociation Study ga ve the fol low ing rehabilitation pref erenc es (com pa red to ne w const ructions) SMALL DIAME TER , "10 LARGE DIAM ETER, "10 REHAB ILITATION (NEW) REHABILITATION (NEW) 46 0 63) FBE COA L TAR 18 13 17 19) TAPE 46 18 33 7 PRECO ATED 18 0 25 0 ASPHALT ENAMEL 4 7 EXTRUDED PE 29 4 COAL TAR EPO XY 18 0 17 0
o o o
o o
e 'raoe is the mos t popular, if not favou red , co ating fo r rehabilitation . _ Mechanica l wheel blasting and urethane coating will give you a rate of -10 m/min on a 30- line .
56
PERMANENTITEMPORARY REPAIRS?
PERMANENTITEMPORARY REPAIRS? • •
• •
•
Pipeline repairs are termed 'permanent' or 'temporary' . For all pipe repairs, the operator needs to perform a structured risk assessment that includes the consideration of all of the potential future damage or deterioration mechanisms over the life-cycle of the repaired pipe system. E.g.: • will internal metal loss of the pipe underneath the clamp cont inue? • will degradation of the elastomenc seal material occur? These considerations will dictate the need for periodic inspection and/or testing to the repair component. The repair component itself may well be regarded as being a permanent repair (a repair component that is intended to remain in place for the remaining life of the piping system), but may requ ire periodic exami nation. A general repair philosophy would be: • replace like-for-like; • temporary repair until rep lacement can be carried out; • permanent repair only where replacement is not practical. ·T""" """''''.'''''''''. ....... P po """,,' _ OuiOOI r..·. UKHee" h "a S.,,,", E.occl ' 0, OHSI-K}f{o TECHNOLOGYREPORT z001lO3!l 2001 Her "'.,"",y ', S", on..". UK. ISBN 0 71/ 6 :10097
Off,,,,,.
11<
57
PERMANENTITEMPORARY REPAIRS '? • USA OPS : ... 'As to the permanency of repa ir, we are not suggesting that the repair sh ould last indefinitely. It need last only as long as the pipe is expected to fast under normal operating and maintenance conditions. '... • . . . '8 qualified repair method must have undergone ' 'reliable engineering tests and analyses" to confirm that the method meets the performance standard. '. ..
O_
:lOOll "-\lo· ' -...sOOT tlo<>ooO ... RSP...... rn
_.,. ,
.-
'"
58
Risk (Integrity) Management Penspen Integrity
1
PIPELI NE MANAGEM ENT, PAPERWORK , SYSTEMS, QUALITY ASSURANCE, TRAININ G.... _ In pipeline engineering , you don't need anyth ing at all ...! . You don't need qua lified engineers, . You don't need quality systems, . You don't need to train anybody, . You don', need risk management, . You don', need management systems , .Yes - you don', need anything! UNTIL SOMETHING HAPPENS...
THEN YOU NEED EVERyTHING••••
2
WHY DO WE NEED RISK MANAGEMENT?
0_2OOIl_,
WE ALL TAKE RISKS
. We all take 'risks': _Fi nancial risks
.Health risks _Travel risks _ Security risks
. Etc In the U K. the annual chance of de ath from:
.00 we calculate these risks?
Cancer = 3 )( 10-3 Injury or poisoning = 3 x 1()-" All types of accidents = 2 )( UP All type s of road accident = 6)( 10 5 All types of accid ents wi th gas " 7 .. 10-1
Lightning" 6 Jl 10 '
•
2
We NEED TO MANAGE THESE RISKS _We all face 'hazards' or 'threats' (anything with the potentia l to cause ha rm) _ e.g . driving , crime, illness , etc .. _ We need to minimis e (reduce the probab ility) our exposure to these hazards , and also the 'consequences ' or being affected by these hazard s e c onsequences such as inj ury, loss of earnings, etc .
a u er ce. we 'manage' both threats and consequences
~ Management of these risks is an important aspe ct of --all our lives. We are all exposed to risk daily, at work and in our private lives , and often mana ge it subco nsciouslv.
'ff
A" ._
But in our business we need to ensure that .;. we think about it actively! ' '""\.}{_.
&,
.I
5
WHAT IS RISK MANAGEMENT? _ Risk ma nagement is a system for dealing with the likelihood that a future event will cause som e kind of harm to , e.g., peopl e, the environment, your business, etc .. _ Risk ma nage ment prov ides strategie s, processes , and too ls to mon itor, re cog nise, and deal wit h a risk event
5
3
WHAT IS RISK MANAGEMENT? _Risk management should be about practical steps to protect people from real harm and suffering
EJ
_ It provides an overall benefit by balancing benefits and risks , with a focus on reducing real risks. ~
Benefit~ .
~
_ It is not concerned with creating a totally risk-free society (impossible), or scaring people by exaggerating or publicising trivial risks _ We attempt to reduce risk to 'ALARP' : As Low As Reasonably Practicable
_ In the pipeline business we are concerned with protecting people. the environment, the pipeline owners, etc .. C P. ' sw' 2000R",,""
7
'S " lIe's in ita lics ba sed on ••!>llemenl by Bill Callaghan, Chair or I ~e Hea ll ~ and Safety Corrwnission, UK, Augu,t 2006
RI S K MANAGEMENT IS N OT A PA NA C EA ' _ Society increasingly asks for 'zero risk' . _ Zero risk is a myth. _ W e are now applying risk management in most industries, but we still experience oil spills, explosions, terrorism , etc .. _ Our risk management processes will not be perfect. _ We are dealing with complex problems, changing conditions, and - always - we have the 'human' factor. _ Failures will contin ue...
4
RECENT 'INCIDENT'
Major accidents happen; for example: . Buncefield, UK . November 2005. • Blast heard 200 miles away. • Europe's biggest peacetime fire. Petro-chern site 9
WHY DO ' I N CI DENT S' OCCUR?
10
5
'I NCI DENTS': Why? _An 'incident' usually occurs when a 'system' breaks down, as most systems have multiple 'barriers' that prevent failure . _ For example, we will be inju red in a automobi le accident if: we are inv olved in an incident; t he automobile does not pro tect us; etc .
_F or exam ~le , for a p i p~ l i ne to fail from co rrosio n, the coalin g must be faulty, CP insuffici ent, inspections fail to delecl, etc .
Threat '" "
~
Barriers
Incident _All the se 'bar riers' will have fau lts (nothing is perfect ), but t he incident will only occu r if all the se fa ults 'line up' .
'I NCIDENTS': Why? -So, ou r risk analysis must look at all threats, all barriers, and all conseq uences , and understand how all these threats and barriers interact.
Threat
Faults
Threat
~arriers
No Incident
In barriers
_ It's a bit like 'Swiss cheese'..
6
'I NCI DENTS': 'Sw i s s Cheese' Model _ The 'Swiss Cheese' model was put forward by Jam es Reason"
_ The basic model's hypothesis is thai 'accidents' can be traced to one or more levels of failure. _ These are typica lly quoted as: e orqanisatio na! influen ces;
. unsafe supervision; a orecondmons for unsafe acts; and _ the unsa fe acts themselves.
'INCIDENTS': 'Swiss Cheese' Model's Barriers a ln the Swiss Cheese model , an organisatio n's defences against failure are modelled as a series of barriers, represented as slices of Swiss cheese. _ The holes in the cheese slice s represent individual weakn esses in individual parts of the system, and are conti nually varying in size and position in all slices .
Potential Threats
- - -
--.
Barriers that reduce potent ial expos ure
"
7
'INCIDENTS': 'Swiss Cheese' Model Failure PTClecti""
'Barn "",'
.~
We. Im"""",, Or 'H ole.
~
_ The system as a whole • produces failures when all of the • holes In each of the slices mome ntarily ahgn, perrnittinq (In Reason's words) "a trajectory of accident opportun ity" , so that a hazard passes through all of the holes in all of the defenc es, leading to a failure
Accident
en- ese holes may be continua lly opening , shutting , and shifting their location!
Q
P.n,,,,,,,soos R . , ~ .' 1
15
PROBABILITY, RISK, GAIN AND UNCERTAINTY
16 1M)
8
RISK: Some quick definitions
• In engineering... • Probab ili ty is 'chance' - the chance of an uncertain event (hazard) occurring; • Reli ab ility .. . is a probabil ity: the probability that a system will perf orm its intended function during a specified period of time under slaled conditions; • Con sequen ce are the effects of the event (hazard) occurring • Risk ... is the combination of the probability of an event occ urring, with its consequence; • Safety .. . is the absence of risk. or the reciprocal of risk . 17 , "'
'RISK': What i s it? _Risk is calculated by combining the ~ likelihood of a hazardous event, with its con sequen ces . ~ _ Risk is easy to visualise ....... _ The lik elihood (or 'probability') of my trousers fa ll;n~
d
.
~I S
. high if I do not wear a belt or braces _ average if I wear a bell , and _ low if I also wear braces.
L
0~"'~Qi·'r"h
.... • c "ll~
, ·. ~" t>. ':tRIN"
~~
.....J .,.......
e 'r ne cons equen ce s of my trousers falli ng down is em barrassment. _ If I'm wearing underclothes I have Jowemb arrassm ent. _ If I'm wearin g no under clothes , I have high emb arrassment
OI'''-:/OOlI_'
ts
9
RISK: What is it? _Risk is calculated by combining the likelih o od of an even t, with its
co nsequences _ Likelihood = 'how often', and a c onsequence > 'how good or bad'.
=
_Risk a functi on of (Probab ility of the event occurring, Co nse quence of the event)
Probability _ _ill
Consequences
I'a ~ Risk 0_
2OOOl "*"" ,
I e:::::::) But what about 'gain... ?
The probab ility of winn ing the U K Lottery with a single ticket. and
ts
getting the jackpot (match 6 of 6 main numbers) is ... 1 in 14,000 .000 .
PIPELINE RISK: What is it?
.Risk ; Probability of failure ,
~
Consequ ence of failure
"
.Failure probability and consequences I vary with the pipeline type. product, environm ent , etc..
~" ""
.", .,
-
C"'"'-"':::>
_ Failure p ro ba bil ities will be a prediction of the likelih ood . over time , of all the likely failure modes in the pipeline. _ Failure consequence analysis will depend on release rate through orifices . toxicity of product . generation and dispersion of vapour clouds and flame jets. thermal radiation hazard s, vapour cloud explosions, etc .. ..... no ... project is risk free . Ri sk can be managed, minimised. shared, transferred or accepted. It canno t be ignored". Q_ _ . . . . .. . . . ~
20
10
~
'GAIN'
- - - - - - - - -- - - - - - - -1 _ I will not take a risk without a
.,
_Illustration : _If I have 51000, and I place it in a deposit account in a bank .. . low risk (of losing the money), but low gain (poor interest rate). _If I place the $1000 in the stock market. .. mediu m risk , medium gain.
.
~
Risk
gain
....... .'
.. . ' ......
.' .'
....
_If I place the $ 1000 on a horse ... high risk, high gain, and also good fun!
•••••••••
Gain 21
BALANCING RISK AND GAIN _I now have to balance this Risk with any Ga in.
• This is controversial: _If I show by risk analysis/management tha t I ca n reduce maintenance costs with only a slight increase in risk, who gains? _The operator ga ins by decreased maintenance budgets , but it is the pub lic who must car ry the increased risk. The public are the losers . _If I increase my maintenance and reduce failu res, the reverse is true.
Never cut costs on operation/maintenance without a risk enalyeistttt
11
UNCERTAINTY & IGNORANCE> _ We cannot know everything: 'uncertainty' is a state of knowledge in which , although the factors influencing the issue are identified , the likelihood of any adverse effects or the effects thems elves cannot be precis ely described. _ This means we have 'im perfec t knowledge'.
e u ncertemty is unavoidable, and has many manifestations (e.g. in knowledge or modelling) and will affect the risk approach. _ A risk analysis will help understand uncertainties
23
UNCERTAINTY & IGNORANCE > _ W e mu st disti nguish between uncertainty and 'ignorance': the latter refers to a lack of awareness of factors influencing the issue . _ Th is is a well- recogn ised weakness in risk assessment, that the ide ntification of hazards may be incomplete. _ The measures needed to counteract this ignorance are a wide use of different disciplines and skilled people
12
IGNORANCE AND MANAGERS' .Management must be careful. ..
_Incidents , and the resulting crises , are sometimes attributed to a combination of: _An accumulation of flaws in an organisation that provide the process for an incident (e.g. the 'Swiss cheese' model); _ The development of managerial ignorance or unawareness that leaves managers blind to this accumulation . • 'Ignorance' has been defined as a manager 's (unintentional) inability to notice , and take into consideration, this cumulating effect of an organisations imperfections. BP Chairman Peter Sutherland . 2007, in statement to shareholders: "Let me say at the ouu et that BP is a great company It has a great oontonc of assets and exceseot people ' C P"" gpeo 2006 Rev&'1 ' C Rou._Wort. ·A ,...;00 ""
25
,,,,poo'Ioct_ ",, '~' '"
,,1.1. "'''"_'''....., A""'"," , ,, " " , _ o n t ",,",,"9 H.....; .....' z005 ZOOM". """ om"",," """
DOWNSIZING AND RE · O RGANI SATION· _ Be aware that majo r change can affect safety.. _ From the Texas City Refinery Report': _ T he balance point between minimum compliance and [safety] optimisa tion is dictated by corporate culture and upper management standards. _ Downsizing and reorganisation can result in a shift more toward the minimum compliance approach . _ This shift can result in a decrease in internal [safety] monitoring, auditing , and continued improvement activity. ,
INVESTI GATION REPORr
R, ,,.,.v E "",<>s ", ~ A N D F,• •
,,, ...... ,,'-.. ..
26
13
'RISK', 'RISK ANALYSIS', RISK ASSESSMENT', 'RISK MANAGEMENT'
0_2005_ '
RISK: 'Voluntary' & 'Involuntary' _ We tend 10 ignore everyd ay risks like riding a bike, alt hough fata litie s from bike accidents are very frequent _ Risks imposed upon us are less acceptable : a fatality caused by a gas pipeline failure will cre ate a huge public react ion and outcry, although such fata lities are infrequ ent. a c c otrast this with smok ing cigare ttes: tobacco is by far the largest source of preventable deaths in the United Slates . Diel and insufficient exercise also cause 1000s of premature deaths . Yet, there is little regu latory effort on reducing smo king . etc .. _ This is because peopl e judg e that smoking is a vo lu nta ry activity, and hence . the resulting deaths are less troub lesome than are other sorts of deaths. _ Hence , the pub lic will accept risks from voluntary hazards (e.q. driving a car) that are many limes greater than from inv o lu nt ary hazards (such as a nuclear disaster). ~-~-,
We are {oath to let others do unto us what we happily do unto ourselves ' Chauncey Starr
za
14
RISK: 'Voluntary' & 'Involuntary'
S moking ... Volunta ry
Pij:2elines .. . Involunta
C""'=r 200li - .
29
'RISK ANALYSIS': What is it? _Risk A nalysis wilt calculate a risk. _ It usually compr ises of five tas ks:
_ System definition. _ Hazard identification . _ Probability assessment.
e c onsecuence analys is. _ Risk results . 'Risk' refer10 to events """"ere ceeoce of occurrence 1$ kroowro If1 advance 'Uncerta i nty' refer10 to events where the ceances are I'l(lI known in advance
From API 581 30
15
'RISK ANALYSIS': Estimating Risk _We can estimate the level of risk: Consequenc e
HIG~
Il il: h
.-<::
~EDI
M~diu m
Lo w
~
~ .
lM/
rJ
~
Probability
Very Lo w
'RISK ANALYSIS': What is it? _Risk ana lysis - the estimation of risk from the basic activity"
System definition
rlde~fify~ Perform risk calculations
Risk Analysis
'".,. 'M", "" ,,, . "'.... ~ ""' . , lJK _
th ' M S"fety E"., ut ,. Cfu..... ' T. ,,,,,,,",,,,, R""""
200 11""3. HS" BOO
16
'RIS K ASSESSMENT': What is i t ? _ Risk assessment - a review as to acceptability of risk based on comparison with risk standards or criteria, and the trial of various risk reduction measu res .' System d finiti n l!denl ify hazardS:1
l'P'ini orm risk calcu fatlons ~ Risk Ana lysis
I Com pare with 'acceptable' risk levels I I
I
Risk Ass essment
's.. ......,.... " " ......... nt', uK ~."h and Sol.". E,ow!".. 0 /"""" om","" H"" OOOKS. """ IsaN0"'. 2231 ,
T""''''''''O\' R _
33
'RISK MANAGEMENT': What is it? _Risk managem ent - the process of selecting appropriate risk reduction measures and implementing them in the on-goin g management of the activity' Systemdefinitfonl
Ilpentifl\haZa'dsi "erform risk calculations Compa re with
'acceptable' risk
,
RiskAna lysis
,
levels
Risk Assessment
Perform cost benefits 1
I
Decisions, Actions, Mitigation
Risk Management
r:
17
RISK ANALYSIS/MANAGEMENT: Summary Hazard s:
W hat could ca use the pipeline to fail or not function correctly or effi ciently? Corrosion, damage by third parties, etc..
Pr obability
Which is the higher probability of occurrence? lightening strikes are un like ly, but corrosion is highly likely on most pipe lines.
Consequences What are the consequences of this threa t occurring? Casualties ? Environmental damage?
Risk Analysis
We can then consider both probabilities and consequences, and assess the overa ll risk associated with ea ch haz ard. Hazards with low probability of occurrence + low consequences would be consid ered low risk . High probability haz ards + high consequences would be cons idered high risk .
From the risk analysis , we obtain a risk value.
Risk Assessm ent
'Assessment' is comparing o ur calculated risk with an 'acceptable' risk
Management
We need to put po licies & procedures in place to bo th co ntrol & mitigate all these hazards an d their consequence s.
0_2006...,..-'
35
SUMMARY: Risk Management and Risk Assessment •
Ri sk M a n ag em ent is an over a ll programme •
II includes ris k assessme nt
• But it also includes mitigation methods , measuring the pe rformance of the mitigation m ethods , organisa tion of m y risk con trol s, etc .. •
R isk A s s e s sment is a n a nalytical p ro c e s s
• Jt identifies all potential hazards to my pipe line and cons equ ences of any adve rse effect ca used by these haza rds
• It compares this risk with a 'ta rget' or 'acceptable' risk • Jt helps in our deci sion m aking , • But, NEVER rely only on you r risk ana lysis to assess the overall integrity and safet y of you r pipelin e • Use risk man ag em ent!
•.
,
36
18
CONTROLLING RISK
37
CONTROLLING RISK OF FAILURE: Location Classes in ASME B31.8
~ ..--''''- '~"
~ tI:::Sl
...... _.
""........orJ/nl".
".",*"g
-==---~..._-
CLASSIFICATION
AREA
Class t (Div 1) Class 1 (Div 2)
0- 10 buildings (rural )
Design Factor (hoop stress/SMYS) 0.80 0.72
cress 2
11-45 buildings (areas around towns)
Class 3
46+ dwellings (e.g . suburban)
0.80 0.50
Class 4
Multi-st orey-type buildings
OAO J8
19
CLASS LOCATION AND INCIDENT FREQUENCY _ A review of 'incidents' (reportable dam age in pipelines) in USA pipelines concluded that incidents/year dec rease with Cla ss location _ i.e. incidents in Class 1 and 2 locations (hig h stress) are less freque nt than Class 3 and 4 areas: _ Class 3 and 4 -0.0045 incidents/year/mile a c tass 1 and 2 -<0.0017 incidents /year/mile _ This can be explained simplisticall y: e mere are more activities thaI could damage a piperine in a suburban area compared to a rural area , _ but it is more comp lex with ma ny parameter s affecting these incident rates.
_.,~. l · ""'"
' - __
_~ ,~
_.
"
""'"
~
... . _ - . oo _
_
39
· , _ " ",
CONTROLLING RISKS •
We can contro l and red uce pipe line fai lures and consequ ences :
•
Pipeline type, design, age, construction quality, product , environment, Company operating practices, maintenance and inspection pract ices, local socia l, economic and political environment , etc.. all affect failure probabilities and consequences.
•
C ontrolling Pr obabilities . Example s: • Damage Prevention: • • • •
..,
One Call System Une Maril.ing or pipeline tape Increased depth of cov er or wall thickness Improved third party informa tion & Incr eased patrol s
• Corros ion Control • CP checks • Rehabilitation or coatings • Pipeline cleaning
•
Co ntrolling Consequenc es . Examples: • Leak detection • Improved emergency planning and response
e"."..,..,2000l R_ '
20
r CONTROLLING RISKS: Effect of Time/Age "
Corros ion failu re freq uency/1000 km year 0.25 0.15 0.05 <1954
19541963
1964-
1974-
1984-
1994-
1973
1983
1993
2001
Year of pipeline construction
CONTROLLING RISKS ('THREATS' ): Example from USA Operator Threats
Main Assessment I Mitigation
External Corrosion
Smart pig (MFL )
Internal Corrosion
Smart pig (MFL)
Stress Co rros io n Cracking
Hydrostatic 'S pike' Test
Manufacturing
Hydrostatic Strength Test
Construction
Hydrostatic Strength 'rest
Equipment
Surveillance
3rd Party Damage
Surveillance I Damage Prevention
Program
Weather Related & Outside Forces
Surveillance f Case Specific
Incorrect Operations
Training 42
21
HOW TO CONDUCT A RISK ASSESSMENT
RISK ASSESSMENT TECHNIQUES _ We have a va riety of risk assessment techniques. Here is a simp le summa ry of techniques tha t can be use d singu larly or in combination" :
Hazard Identification
This is usua lly a list of all possible hazards thai might a-ise.
(HAZID) Hazard and Operability Study (HAZOP)
HAZOP closely examines the plan t proc esses and identifies expected and une xpected hazards . The con sequences of thes e hazard s will be considered, and methods of mitigating or avoid ing them w ill be planned .
Risk Assessment
W e can use qua litative , quantitative m ethods to esta blish the relative import ance of any risk
probability Modelling
Fau lt tree analysis, Event trees, Block diagrams , Causecons equ enc e diagrams , etc
e&fi$equence AnalySis
This can be used to asses s the outcome of a hazard and check that mitigation methods a re in place .
Fai lure Data Collection and Analysis
Pub lished or field data on fa ilure s, etc., can be used in the abo ve techn iques, and the y can give 'acceptable' ris k levels.
..
"- .
22
RISK ASSESSMENTS· KEY EL EM EN T S
Determine if and why you want a Risk Assessm ent
Who ""';11be involved In the Assessment , and wi ll it be Accep table to R ural Authorities?
Estimate Failure P ROBABILITY
IDENTIFYall Hazards
Estimate Failure C ONSEQUE NC ES
Identify person/group
who can do the Assessment
Estab lish Database of Pipel ine, Route and Plant
Estab li s h and Agree
Calculate
ACCEPTABLE RISK
RISK
LEVELS sess If Company will
Implement, Control Review and Audit
Document all Analysis
r - -- lAcce pt RIsk (compared to Gain
,
---------------'
RISK ASSESSMENTS: Simple - Qualitative· Approach Qualitative risk assessment matrix
w
Ow
Zo::
W::J ::J ....l
@tt (flLL
6o 0
Pipeline
High
B
Low
A
Pipeline D
Medium
High
Pipeline
Medium
Pipeline E
Pipeline C
Low
PROBABILITY OF FAILURE This analysis gives us a RELATIV E risk , or a RANKING , II does nol give us a risk value. on ly a COMPARISO N. C_
2OOli 1l_
l
23
RISK ASSESSMENTS: Complex - Quantitative· Approach _ We can conduct a QUANTITATIVE risk assessment (ORA) _ These assessments calcu late ABSOLUTE risk level s on both individuals and g roups _ We calcu late a 'probability' of becoming
casually. _ E.g. 1 in a million chance of injury/annum _ We compare this calculated prob ability with a 'target' or 'acceptable' pro bability _ This targeUacceptable probability m ay be obta ined from ou r Regulatory Body _ QUANTITATIVE risk assessm ent will involve det ailed calculations, using software. _ Some commercial software is available
-I
. "'-j,' ~..-.:=--~ .rJ ;-. ~ ~
- '.
Risk
=Pt x C t
Risk < Acceptable
QUANTATIVE RISK ASSESSMENTS: Example 'QRA' A lgorithm for Pipeline Identify Hazards
, Determine Failure FreQuency'
I
,
Assess
Hca'C u,atel Risk
Failure Modes
t,
,, ,,, ,
1-
LJ Determine Outflow
I gn it iO~tvH IThermal Probabilit Radiation
________________
Radiation ~
Effects
-IMitig atio n?
I AssessJ
lB~sult.J
?. Make
Decision !
",.
)
24
QUANTITATIVE RISK ASSESSMENT: Example for Gasoline* Probability
X
Consequence of Event Probability of ignition
of Event
. .
~,
Immediate
Delayed
Ignition
Ignition
V.,
Pool Fire
0.031
0.031
V.,
Pipeline Release km years"
I~Most "likely consequence of
No
gasoline release Unignited..c: (94%) Is un-Ignited Pool ~;I of gasoline
No 0.969 ~"'csp>n l(l()6
Ro, 6i '
R•
ceo
'acc eptable ' risk
0.030
0.969
For a rup'u", ,., a o ur ~3"
I1IIJII(> with
Pool Fire
0.03 1
0.30 to 0.57/1000
Compare
Consequence Probability
0.939
r., ..., I", ,,, R,,", 1,,,,,, Ga,oI"", Plpol,,,,,, '0 th~ UOI1.o Kingdom HSE Coo,,,,,,,
.-,ct1 R. ".,., e RR l 06i l 899 , Hea lth & Soafety 1999 ""'\I" dor->«' on w ' '';d<,-''''',"""oo,",e E .OOJ ~' ~ ,
"
" T~ "' ",, ' ''' ' ''''' ( "''' '''''''' '
("I )
QUANTITATIVE RISK ANALYSIS: Difficult t o app ly •
Popular for pipelines in Europe and Canada, but not popu lar in USA and Latin America
!1. 1,06 00
.,!
~ ' .06 ,07
1.0,,-00
1.o ~_10
I-
,
-
J-_-J ' 00
25
QUANTITATIVE RISK ASSESSMENTS: Linking Risks to Public Concerns · e v artous studies have established that hazards give rise to conce rns which can be put into two broad categ ories: _1 . Individual concerns , or how individua ls see the risk from a particular hazard affecting them and thing s they value persona lly, i.e. how does the risk affect them, their family and things they value.
• People may be prepared to engage voluntarily in activities that often involve high risks , but usually they are far less tole rant of risk s imposed on them and over whic h they have little con trol. unles s they consider the risk s as negligible. • Moreover, though they may be willing to live with a risk that they do not regard as negligible . if it secures them or society certain benefits, they would want such risk s to be kept low and clea rly controlled .
~
~~<;, .
• 2. Societ al concerns (see next)
QUANTITATIVE RISK ASSESSMENTS: Linking Risks to Public Concerns · a vartous studies have established that hazards give rise to conc erns which can be put into two broad catego ries: _1. Individual conc ern s (see pr evious)
_2. Societa l co nc ern s: these are the risks or threats from hazards which imp act on society and which, if realised, could have adver se repercussions for the institution s responsible for putting in place the provisions and arrangements for protecting peo ple. e.g. the Govemment of the day. _ This type of concern is often assoc iated with hazards that give rise to ris ks which , were they to materialise, could provoke a socio-pol itical response, e.g. risk of events causin g widespread or large scale detriment or the occur rence of multiple fatalities in a single event. _ Typical examples relate to nuclear power generation or railway travel. _ Societal concerns due to the occurrence of multiple fatalities in a single event is known as societal ri sk .
52
26
QUANTITATIVE RISK ASSESSMENTS: Linking Risks to Public Concerns'" l' I"" ">I"~f,I ,
....,~j,, "
T"irf~!J/ ..
n'w""
lJroa,jJ,- an-",,' "hi ..
,...~; ""
'Roow'g """ .
"""act",\) """'"" HSE .' doc",,,,,",","',," p~ .
53 HSE Boo'" KI P;>, 2001
QUANTITATIVE RISK ASSESSMENTS: Linking Risks to Public Concerns Risk
1
0 s eing InjlJred
la nn um
0 Having a
0
ecctoent 0
0 Death by cancer
0.000 1 Killed by car whi le walking
0 Accidental drowning
0,00000 1
Death in o airplane crash
Low
I
Tolerable
I
o Killed by 0.000000 1
Unaccepta ble
accident
heart attack
Death by
0
Automobile
Acceptable
light ning Degree of personal cont rol
High
Being killed/inju red by a pipeline failu re is 'invo luntary' risk
27
QUANTITATIVE RISK ASSESSMENTS: Types Of Risk _ Risks from haza rdous installations are of interest to both the individual who might be inj ured , and 10society in general. _ This mean s we must conside r two types of risk: . 'Individual' risk is a measu re of the risk to an individual who ~ .might be located at any point in the effect zones of incidents. A ~~ ~ mo re formal definition is... -yo \ . 7 he frequency at which an individual may be expected to sus tain a given level of 'harm from the rea lisation of specified haza rds '. _An example of indi vidual risk is the risk of being killed in a road accident in the UK about 100 in a million per year, on average. _ It should be noted thai individual risk is the same whe ther there is actually one person at risk or many persons at the same risk . • 'Soc ie tal'
RISK ASSESSMENTS: 'Complex' Approach ••• Types Of Risk . Risks from hazardous installations are of interest to both the ind ividua l who might be injur ed , and to society in general. . This me ans we must consider two types of risk : . 'Indi vidual ', . 'Soc ietal' risk is a measure of risk to a group of people in the effect zones of incidents . A more formal definition is ... • ' he relationship between fr equency and the n umber of p eople suffering from a specified le vel of harm in a given population fr om th e realisation 'I: of specified hazards '. • An example of societal risk is air travel, where there is a 1 in 10 chance of a major disaster in the U.K . per year. • It is the reaction of soc iety which distingu ishes societal risks . (e.g. an oil rig disaster), from the more famili ar risks (e.g. m otoring ), even thoug h the latter may result in mo re death s/year
28
INDIVIDUAL AND SOCIETAL RISKS AROUND A PIPELINE To reduce risk: re locate line. reduce pressure, etc .. This is expensive.
,
Individual within a certain distance from the pipeline ('pro Xim ity') , or above a spe cified populati on density,
At risk 'X'
0_
o:~.
'''.,.>, ~ S.
2005 _'
!- ..
~ s1Jl Ystf Individu als within proximity, o r abov e a specified pop ulation density.
All are at risk 'X', but beca use we have a 'group' we must consider 'soc ietal' ris k 57
OUTLINE OF A QUANTITATIVE INDIVIDUAL RISK ANALYSIS
=
_ In div id ua l Cas ua lty Risk Failure Frequen cy x Failure Cons equ ences Failure Frequency Incident Frequency (PI) x Failure Probability (? ,)
=
_ Failure consequences depend on four main factors : . Probability of ignition, P9
. . . .-
- Exposure probab ility, p.
..
. Probability of Being a Casualty, Pc . Probability of interaction of failure with prope rty, P, _ Therefore: Ind ivi d ual Cas ualty Ris k - Pi X PI X Pr X P9 x P,
X
p.
Remember: Risk Ana lysis will tell us HOW OFTEN somethi ng will happen, bul it will nol tell us WHEN il will happen .
se
29
OUTLINE OF A QUANTITATIVE INDIVIDUAL RISK ANALYSIS • Individual Casualty Risk = P I x Pf x P, X P\I X Pc X p . _ Some quoted values are: •
Pi
X
PI = 4.5 x 10~ per km year for a rupture
•
Pc = 1
•
P, = 154 per km for a 9 14 mm pipel ine
•
Pg = 0.5 P, = 0.63
•
_ Giving: Ind ividual Risk = 0.2 x 10-6 per y ear
59
'A C CEPT A B L E' FAILURE PROBABILITIES (EXAMPLES ONLY) OFFSHORE
Limit States Ultima te
Serviceability
ONSHORE
ACCEPTABLE FAILURE PROBABILITIES (per year) SAFETY ZONE
OPEN WATER
10 -6
10"3 _ 10..4
10.1 _ 10.2
10.1 _ 10-2
10 .5 _
TARGET FAILURE PROBAB ILInES (per km)
Limit States
MORE SERIOUS (Urb an)
LESS SERIOUS (Remote)
Ultimate
10.7
10·
Serviceability
SERVICEABILITY
10"3
o _ ~ _.
30
'ACCEPTABLE'INDIVIDUAL RISKS (FROM THE UK) INTOlERABLE
1 IN 10.000 years A$ LOWA$ IS REASONABLY PRACTICABLE
1 IN 1,000,000 yea rs REA SONABLY ACCEPTABLE
3 lN 10,000 ,000 years ACCEPTABLE
Lower probab ilities approac h 'zero', i.e. 'never'. A value of 'never' in the pipeline business has bee n quoted as 1 x 10-12 s.. 1( "'-*-.' ~~Rr$k~.
_
_pipelinensk _a>m
'ACCEPTABLE' INDIVIDUAL RISKS (FROM THE UK) _ These levels were obtain ed by the UK's Health and Safety Executive from consideration of accident statistics in various indu stries (ignoring high risk occupations such as helicopter pilot) _ A risk of death of about 1 in 1,000 per annum was con side red 'jus t' tolerable to society for a 'normal' working popu lation.
_ The HSE then cons idered the death of a membe r of the public fro m a large sca le, hazardous industries. HSE proposed a tolerabl e figure of no less than 10 times lowe r: 1 in 10 ,000 per annum In the UK, the annual chance of death from : Cancer = 3 x 10-3 Injury or poisoning = 3 x 10'" All types of accidents = 2 x 10'" All types of road accident = 6 x 10·$ Lightning
=6 x 1O~
In UK industry, the annual chance of death: All employees = 8 x 1O~ Mining and Quarrying = 1 x 10'" Construction = 6 x 10 '$ Agriculture, forestry = 6 x 10·$ Service industries
= 3 x 10.{i
31
'ACCEPTABLE' INDIVIDUAL RISKS (FROM THE UK): The 'ALARP' Principle _ The ALA RP principle is established in law in Britain by the 1949 case of Edwards vs. the National Coal Board _ Here it is sta led that.. .
• the case established that a computation must be made in which the quantum of risk is placed on one scale and the sacrifice, whether in money. time or trouble, involved in the measures necessary to avert the risk, is p laced on the other; and that, if it be sho wn that there is a gross disproportion between the m, the risk being insignificant in rela tion to the sacrifice, the person upon whom the duty is laid discharges the burden of proving tha t compliance was not reasonably practicable.
63
' A C CE PT A B L E' SOCIETAL RISKS (FROM THE UK ROYAL SOCIETY) 'F-N curves' are a graphical repr esentati on of the relation ship betw een the annual probabil ity of an event causing N or mo re fata lities, and the number of fatalitie s; this being a com mon way of expressing societal risk issu es .
,
E
0. 1
c c
e
~
~
CI
~
z~
0.01 0.001
0.0001
10
100
1000
10000
No. o f Death s , N
32
r: BEING 'REASONABLY PRACTICABLE" _ W hat if the cost of reducing the risk to 'ALARP' is very high, or the reduction impractical? _ Risk management aims to be 'reasonably pract icable': this mean s that we have to take action to control the safety, environmental, financial , eic. . risks , except wh ere lh e cost (in terms of tim e and effort, as well as mo ney) of doing so is "grossly disproportionate " 10 the reduction in the risk. _ W e can calculate this (see prev ious. and later ). or we can simp ly apply accepted 'good practice' .
Cost
Risks
BEING 'REASONABLY PRACTICABLE': Good practice * • 'Good practice' refers to practices that have been acknowledged by HSE or local authorities as representing standards of comp lian ce with the law. _ II doesn 't mean "custom and practice " necessa rily - that can be poo r practice e ano 'good pract ice' would be co nsidered a 'minimum requi reme nt'
. Examp les of 'good practice' are : .g uidance produced by other government departments; a stanoaros produced by Stand ards-ma king organisations (eg . ISO , BS, CEN); . guidance agreed by a body (e.g . trade federation, professiona l institut ion, sports governing body) representing an ind ustria l/occu pational sector; . et c.. 66
33
BEING 'REASONABLY PRACTICABLE': Cost of Life (Fro m the UK) in 'Tolerable' Region _ The question now is... 'How much would we be prepared to pay to reduce the risk of dying in an accident?'
Transnort Benchmark
Cost ($millinn) 1.5
1.3 R"il
?f1
Air
29
BEING 'REASONABLY PRACTICABLE': Co s t of Life Fr o m the USA Office of Pipeline Safety' (2004) For use in Cost/Benefit analysis
Injury
Cost ($million)
Fatality
3
Serious injury
0.5
*Doc ket RSPA 00-7666 356
68
34
r: COST OF FAILURES (FROM THE USA) Office of Pipeline Safety' (2004) Repair (non- leaking) to gas pipeline
$20,000 to $40,000
(depends"" wtlet her supply is interrupted)
Repair (leaking) to gas pipeline -$200,000 to $400,000
Major fa ilure to gas line
-$5,000,000
*Docket RSPA 00-766 6 356
MANAGEMENT OF RISK... using 'systems'
r-
O P.,.,.., 2006 R",,6i'
35
MANAGERS & RISK MANAGEMENT _ Risk 'management' requires manage rs! _ This management elem ent should not be underestimated. _ Management must implement the full risk management process , and this can be difficult. . Managers need to put in place systems that allow a full risk assessment to be conducted, its recomm endations implemented, and the performance of the system reviewed and audited. _ This might not be easy... • _ a manager may not be able to anticipate major incidents. as he/she will have basic assumptions about him/herself, jheir position . their company. the wo rld, etc.. and ... • collectively, managers may have shared-beliefs about possible incidents
_ How can we put a system in place?
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MANAGING A PIPELINE SYSTEM . W e control risk s. by managing them _A pipeline system has many types of plant. buill using differing codes, and under differing regulations:
Y ASSET S
REGULAT IONS
CO DES
PROCESS PLANT
PRES St)RE S STEk1S
PIPELI NES : TRANSMISSION
HAZARDOUS PLANT
PRESSURE
PIPELINE SAFETY
ESSElS
RI8UT10N
ASMEVm, ETC
DIFFERING MANAGEMENT SYSTEMS NEEDED e.g.ASME 831.8S
36
MANAGING A PIPELINE SYSTEM: Management Sy s t e m _ A Management System is a management plan _ It is a document, that explains to com pany starr, customers , regu latory authorities, etc., how the com pany and its assets are managed , by stating: . who is responsible for each aspect of the ass et and its management. . what policies and processes are in place to achieve targets and goa ls, _ how they are implemented _ how performance is measured, and final ly,
e how the wtlole system is regularly reviewed and audited
_ The document is agr eed al board level .Many companies operate such a system in a piecemeal , or unstructured manner _ II is the production of a single. detailed document that encompasses all the above asp ects thai creates the 'system'
MANAGEMENT SYSTEML Key Elements Policy Organising
I
I
A~d.i\i;'9
;j---.
\:
Policy development Org an isationa l deve lopment
Planning & Imp lementation Meas~ring
Performance Reviewin g Performance
Deve loping techniques of planning, measuring and review ing
Feedback loop to Improve performance
37
PIPELINE INTEGRITY/RISK MANAGEMENT SY ST EM f
~' !
I
Auditing
I-
Integrity Manag"ment Organising
I
Planning & Implementation
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Measuring Performance Reviewing Perform~nc~,
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38
PIPELINE MANAGEMENT SYSTEM Implementation 1. Pi peline Integrity Man agement Sys tem Philosophy, responsibilities, performance measures, review and audit proced ures, and the overall integrify program L..- ,'"nt"egri!y' , Manage ment Plan & Schedule
Risk Assessment
2. Pipeline Int egrity Implemen tation Pl an (Inspection and mitigation methods and procedures)
!:-:__--;c---c::-:~Wc:.::h=O~d~oe=s~ what. when and how. .,,--:_"::--:,-' Assess & collate results anal is tools} & Rep.airs
Feedback
3. Database Management & Applications Collate and update all data
...
~ U ~ at e ~ p l i ca tions
e.9,/ .G £
0_2005_,
~
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DATA MANAGEMENT
piI
Database
APPlicationA~
Applica tion
fiIIiII1iiI sJSJi'
Database A pplic ation B
Database Applicatio n c.... ~~~~'
Data App lication Domain
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39
DATA FORMATS
100
=
"
O D lg lt a l
o Paper
80
%
60 40 20 0
JI 1995
~2005
...
Documents produced!information available
79
Recent Changes in 'Integrity' Regulations & Standards in the USA
Penspen Integrity
.tUS Regulations on Integrity Management Liquid & Gas Lines ./ API 1160 Integrity Management of Liquid lines ./ASME 831 Integrity Management of Gas lines
80
40
RECENT PIPELINE SAFETY IN USA There have been a number of very high profil e, tragi c pipel ine accidents in the past coup le of yea rs in the USA , The most emotive was a 1999 failure of an onshore pasolene line (see right) - il leaked into a river, and a subs equ ent ignition killed th ree young people who wer e playinglfishing in the river.
Unfortuna tely, it doesn't stop the re - another big failure of an onshore gas line in New Mex ico in 2000 killed 12 campers (see right), and we are now faced with a very unpopu lar pipe line indus try in the USA and a regu lator unde r siege.
81
US Department of Transportation
82
41
DOT, USA 'FINAL RULE': Liquid Lines· 49 CFR 195.452 (B a c k 9ro u n d) _ In 2000 , the U.S. Departme nt of Transportation (DOT) proposed regulations that require pipeline integrity validation throug h inspection, testing, & analysis of pipelines that run through/nea r high consequence areas (HeAs). _HCAs are high population areas (e.g. 10.000 peoorezsq mile), 'busy' commercial navigable waterways , enviro nmental sens itive a rea (as defined in 49 CFR 195.6),
_ OPS is issuing integrity management program requirem ents in several steps . _ Natural gas and hazardous liquids have different physical properties, pose differ ent risks , and the configura tion of the systems differ,
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_ OPS has begu n a series of rules by issuing requirements' pertaining 10 hazardous liqu id operators ,
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.......
83
FINAL RULE: Liquid Lines. Requirement · General _ The rule requir es operators to dev elop and implement a written integ rity management plan . This plan must: _ Identification of all pipelin e segments that might affect a high consequence area, should there be a failure, (to be completed by end of
2001) _ A plan to perform a base line assessment of pipeline system by specified dates , e.g. sma rt pigs. hydrotesti ng, etc .. (to be completed by March 2002) _ Integrity assessments conducted after 1995 may be considered acceptab le. provided they comply with the provisions of the rule
.. 42
FINAL RULE: Liquid Lines. Requirement - Integrity Management Plan _ The Plan must contain : _ A process for identifying which pipel ine segments cou ld affect a HCA _ A baseline assessment plan (see next slide) _ An analysis that integrates all avai lable information about the integrity of the entire pipeline an d the consequences of a fai lure e c rnerta for repa ir act ions to address integrity issu es raised by the assessme nt methods and informat ion analysis _ A continual process of ass essm ent and evaluation to maint ain the integrity of a pipel ine _ Identification of prevent ive and m itigative me asures to protect the high consequence area _ Methods to m easu re the effective ness of the prog ram _ A process for review of integ rity assessment res ults and information analysis by a qua lified person 0_2006_-'
85 5ee h t1p ' ~ ~ _
~hIm
FINAL RULE: Liquid Lines. Requirement - Baseline Assessment _ Baseline assessme nt must includ e iden tificat ion of all pipeline segm ents, m ethods to assess integrity, sche dule for integrity assessments , and explana tion of all risk factors. _ Following the base line assessment, a risk analysis is required on any segment impacting HCAs _ Note that smart pigs ar e not considered suitable for ERW or lap welded pipe with a failure history _ T he baseline assessment must be 50% complete by Sept 2004 , and complete by March 2008 .
0 _
20061le¥61'
r:
43
FINAL RULE: Liquid Lines. Baseline Assessment (a pipeline's first integrity assessment) _THE ASSESSMENT . ', ..all of the actions that must be performed to determine the condition of the pipe and to repair it if conditions wanant. This inclu des
f'
r
conducting intern al inspections or hydrostatic tests ,:~~--7 FI or implementing other technology that pro vides an equivalent understanding of the condition of the line.. . I .J I . l "'and the resulting evaluation, excava tion , and repair. ' • _. _ ._~ _ IT MUST INCLUDE ._~
. ',.. a written plan for performing the baseline assessments necessary /0 assure pip eline integrity for each pipeline segment that could impact an HCA It must include : , I I - Identification of all the pipeline segments that can affect an HCA - The integrity assessment method, or methods , planned for ~ use on each identified pipeline segment - A schedule for assessm ent of each identified segment '~ - An explanation of the technical basis for the integrity assessme nt methOd(s) selected and the ris k factors used in schedulin g the assessments.'
E ,
i
0_""""_'
FINAL RULE: Liquid Lines. Progress in 2004 _ There are ~ 1 60 . 000 m iles of onshore and offshore liquid pipelines in the USA . _ The number of pipeline segme nt m iles that could affect HCAs is -70,000 miles. e r rese HCA seg ments constit ute approximate ly 43 percent of the total liquid oicetm-s in the Integrity Management (1M) program , _ In 2004 . the Total Pipeline Miles Inspected due to the liquid integrity managem ent require ments was -95,000 Miles. _ This m ileage includes both the miles Inspected In pipe line segments that could affect HCAs as well as the miles inspected coocoenr WIth the HCA inspectlons required by the LIQuid 1M Rule. _ The number of pipeline segment miles Inspected thai could affect HCAs was ~24 .000 mi les. _ There were ~ , .700 ccoetcos repaired Of mit igated in pipeline segments that could affect HCAs that were classified as needing 'Immedlate "attention, and -3.800 other ccontcoe were repaired Of mitigated on a 'sceeo urer basis as reqered by the LIQuid 1M Rule. _ In 2004 , there were more than an additional 11,000 anom alies repaired Of mltigated both WIthIn pipelin e segmen ts that could affect HCAs and In pipe segments that could not -tnat were not reqoeed by the l iQuid 1M Rule
88
44
r> FINAL RULE: Gas Pipelines· 49 CFR Part 192 11!'t9C il (Background) _U SA DOT has issued a final rule for* transm ission gas lines (methane, hydrogen...) on Pipeline Integrity Management in December 2003
0~
.,
-.
s ----
r'
_ Relies (quotes) heavily on A$ME 6 31.8S e o oerators mu st ident ify 'high consequence areas ' _ Must have an integrity mana gement program _ Identify all threats to the pipeline in these 'HCAs' usi ng risk assessment - ASME 631 .8$
.~
>
.
r
........
---~ .
_-'-'-"'_ __
"" O:~._
8
'HCAs'
_H CAs:
=
_ Class 3 and 4 locations ~ g _ There are excep tions based on building density with in ...n... -.n. an area around the pipeline ~ n [J [] [] J;I gl • An area of a circle of threshold radius 1000 feet or large r 0 0 that has a cluster of 20 or more build ings Intended for human --" occupancy. ~ T.)
I
e Peo"",o 2006 "".61 1
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ao~y to9a5 93'M",g ",d, " '", 'on
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FINAL RULE: Gas Pipelines . 49 CFR Part 192._ Q I nte9rity Management Flowchart
il
1. Ident ify 'h igh conseq uence areas' : Use cl ass locati on or 'impact circles'
~
2. (a) Identi fy Threa ts and (b) Perfor m Ris k Assessment
~I
3. Produ ce Baseline Plan
~I
4. Remediation
<,
2006 R..,..,6I1
I
"'S.) \ dditional Preventative & Mitigation Measures
~r c·PO' ''''''"
I
6. Continual Evaluation & Reassessment
J 90
'"
45
FINAL RULE: Gas Pipelines. 49 CFR Part 192. Progress in 2005 '
'!i, ~"
a There are -295,000 Total Gas Transmission Miles of onshore and offshore pipeline in the USA a There are -20,000 Total HCA Miles (-7%of the Total Gas Transmission Miles ) a During 2005, the Pipe lin e Miles Inspected due to the gas in tegrity ma nagement requireme nts wa s -20,000 Miles (- 7% Tota l Gas Transm ission Miles . _ This m ileage includes both the pipel ine miles outside of HCAs (inspected dUrIrIg the HCA inspections) and the pipeline miles of HCA.
_ The HCA miles Inspected wa s nearly 2,800 . Pipeline operat ors completed ne arly 240 Repairs clas sified as ne eding 'immediate' attention and roughly 400 Repairs class ified as 'scheduled' in HCAs. _ There wer e 10 "incide nts' (involving damages 01$50 ,000. injuries, or fatahlles ) Wlth Third Party Damage _ There were 104 'l eaks' in HCAs with equ ipment and external corrosion being the leading ca uses or the leaks . _ There were 20 failures (dee med unsuitable lor ccouooeo operation but no release of ga s occurred) 'Mth external corrosion being the leadin g cause ol l ailures .
O_2o:lI_'
., sr
STANDARDS/CODES FOR PIPELINE INTEGRITY MANAGEMENT _ There are two published documents that give guidance on Pipeline Integr ity Management: _Liquid lines: API 1160 _Gas Iines:Supplement S o f A SME 831.8 _They both require a detailed integrity manag ement 'program' , that includes an integrity man agemen t 'plan'
PIPELINE INTEGITY MANAGEMENT I
I
API 1160
ASME B31.8S
rogra
46
American Petroleum Institute: API1160
93
INTEGRITY MANAGEMENT PROGRAMMES & API1160 _The Office of Pipeline Safety (OPS) requires operators of HCA pipe lines to have an integrity manag em ent pro g ram that continually assesses and evaluates the integrity of He pipe lines. _API has produced a standard on pipel ine integrity ma nagement based on industry experience and prac tices _ T his st andard int end s to provide a ba si s for a c om pany's approa ch to complying w it h the ne w Regulati ons (CFR 195.452) of the USA DOT. _This standard-development initiative is titled "Managing System Integrity for Hazardous Liquid Lines", 1st Ed., API Standard 1160-2001. _ It was published in November 2001 (hltp: /lwww,ap i.orgicaU)
47
INTEGRITY MANAGEMENT PROGRAMMES & API1160 - H igh Con s equence Areas aAPI1160 defines 'high consequ ence areas' as: . high population area - urbani zed area , containing 50,000 or more people and has a population density of at least 1,000 people per square mile . a other populated area - concentrated popu lation, such as an incorporated or unincorporated city, town , village, or other designated residential or commercial area . • commercially navigabl e waterway - a substantial likelihood of commercial navigation exists . e area of the environment that has been des ignated as unusually sens itive to oil spills - an unusually sensitive area ('USA')
95
I N T EG RITY MANAGEMENT PROGRAMS & API1160 aAn Integri ty Management Programme: etoennnes & analyses all events that could lead to failure _ Exam ines likelihood and consequences of potential pipeline incidents _ Exam ines and compares all risks _ ProIJides a framework to select and impleme nt risk mitigation measures _ Established and Tracks performance, with the goat of improvement
_The programme starts with a good pipeline design & construction, and satisfying all other lega l and code requirements _ It is flexible _ It is built on trained people, using define d processes _ Integration of all informat ion is a key requirement _ It should be tailored to an operator's needs _ It should be continually evaluated and reviewed internally _An integral part is a risk assessmen t, and this is a continuous process _ It m ust take action when significant damage , etc" is detec ted or expected _ It should use new technology as appropriate _ It should be internally and externally audited _ There is no 'best approach' ,
48
r: FRAMEWORK FOR INTEGRITY MANAGEMENT I!l!l!l!iI: b PROGRAMS: API1160 Identify Potential Pipeline Impact to HCAs
Initial data gathering and review Initial Risk Assessment
Develop Baseline Plan
Revise Inspection/Mitigation
Update Data
Reassess risk
1 Manage Change
BASELINE ASSESSMENT PLAN IN API1160 _ The Baseline Plan is de ve loped after gathe ring all nec essary data , and hav ing conducted the risk assessment e w r en developing the Plan, an oper ator shou ld consider:
. Pipeline ano malies tha i may lead to failure _T he inspection techniqu es available . Methodologies for eval uation of in line inspection data . Pipeline repair m eth odo logies and other mitigation activitie s
_ The Plan consi sts of: _An initial ins pection plan _ T he most appro priate ins pection method for each seg ment must be ident ified _ E.g . hydrotesting or sm art pigs _ The ins pec tions should be prioritis ed _ Possibly some mitigation measures , includ ing a schedule _ E.g, mitigating sp ills
r>
98
49
l'I.\i!l.'!'
RISK ASSESSMENT IN API1160
_ The goal of a risk assessment is to iden tify and prioriuse all pipeline threats _ Risk assessments are con tinuous processes, and shou ld be part of the comp any 's daily processes. They wi ll need data Errors US>n!J IfIMI8quaIe da ta 8ITI much _ Absence of data will lead to uncertainty Jess /Jl,Jtl thc~ usiIg no datB 8 f air.
_ Don't panic! Flag up data gaps , and go oul and generate that data
Charles Bab bage (1192-1811)
. You can perform your initial assessment us ing limited data _ A learn app roach is best for risk assessment, so adeq uate resources are needed. _ Steps are : _ Form expert team' Agree structured approach . Identify risks using past/present data. but focus on possible future mishaps _ Quantify and rank risks . Mitigate high risks _ Review and audit _ Ensure a feedb ack loop as new data is con tinuously generated _ Start again! " II
StaII_ ~_"-""IIknowIedgft._ . _1_WIIurft*",_
_n
... 'h_o
99
PERFORMANCE MEASUREMENT: API1 160 _ W e ne ed to evaluate how effective our integrity m anag em en t program is'
_ Did you do what you said you were going to do? _ Was what you said you were going to do effective in addressing the issues of integrity in your pipeline _ A PI 116 0 requires at le ast 10 performan ce measu re s . _ TM y shal l includ e: _ A goal to reduce the number of unintend ed releases, WIth a goal of 0 releases. _ A goal to reduce the volum es of releases, WIth a goal of 0 releases. _ A measure of integri ty management activities completed in a year. _ Effectiveness of a company's commun ity 'outreach' activi ties . _ A narrative of the system, and a record of its improvements. _ They should indude: e oer coseeucothat high risk areas have been reduced _ Intemell audit showing improvement _ Extema l audit showing improvement e o enonsneuco that operational events (e.g . SCADA outages ) are imprOVIng e oemonsueuoo that the risk associated WIth Iachnes and term inals are decreasing with
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50
American Society of Mechanical Engineers (A5ME) - A5ME B31.85-2001
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A5ME & INTEGRITY MANAGEMENT: A5ME B 31 .85-2001 . In 2002 The American Society of Mechanical Engineers (ASME) has produced an integrity managemen t appendix for its ASME 8 31 code. • 'Managing System Integrity of Gas Pip elines' , ASME 631 .8S-2001 . Applicable to onshore pipelin e syste ms co nstructed with ferrous materials th at tr ansport
~ III •
9 0s . It is similar to API 1160, but is specifically related to gas (ASME 8 31.8) pipelines. • Under this ASME initiative. there are other documents being produced by organisations such as the National Association of Corrosion Engineers (NACE) that will contribute to integrity management. . Students are directed to the websnes of ASME, NACE and also the US Office of Pipeline Safety for further, up to date, information.
'"
51
ASME & INTEGRITY MANAGEMENT: ASME 831 .8S-2001 . 'Ma nagi ng System Int egri ty o f Gas Pipelines ', AS ME 8 31.85-2001 • 'A comprehensive, systematic and integrated integrity managem ent program provides the means to improve the safety of pipeline systems. Such an integrity management program provides the information for an operator to effectively allocate resources for appropriate prevention. detection and mitigation activities that will result in improv ed safet y and a reduction in the number of incident s. ' _ II is similar to API 1160, but is specifically related to gas (AS ME B3 1.8) pipelines,
SAFETY
'03
ASME & INTEGRITY MANAGEMENT: ASME 831.8S-2001 _ This standard describes a process that an operator of a pipeline system can use to assess and mitigate risks in orde r to reduce both the likelihood and conse quences of inciden ts . The standard covers both a prescriptiv e and a performan ce based integrity management program . • Integrity Management Program ASM E 1-13 1.1)$-2001· !nlcgny Elements in A8 ME 831 .88 2001.
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A5ME B31.85 & INTEGRITY MANAGEMENTIdentify 'High Consequence Areas' _ The USA regulations require integrity management in all 'high consequence areas '. _ These areas can be identified eithe r by Crass Location of 'potential impact circles " (see nex t)
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---~ --:;. ..-
"-'- 1 -'--_...--.. -=--
'"
A5ME & INTEGRITY MANAGEMENT - ' Im p a c t Areas' i n A5ME B31.85 .'""""'.. ,Ii"ff( 'T ) _ We need to know the size of the area around our pipeline thai woul d be affected if the pipeline was to fail. _ We will call thi s the 'refined radiu s of imp act' _ ASME 831.85 gives us guidelin es on calculating this radiu s. _ It is based on work at the G as Resea rch Institute _ The affected area extends from the centre of the first affected circle to the cent re of the last affected circle _ The number buildings in the affected area can then be used to determine a relative consequence of a rupture for this pipeline segment
""
53
A5ME 831.85 & INTEGRITY MANAGEMENTIdentify 'High Consequence Areas' .The USA regulations require integrity management in all 'high consequence areas'. .These areas can be identified either by Class Location of 'potential impact circles* (see next)
...
____ legen d .__
_- ,
0
.......,ssmll!'Nl
o o
Comm u n;<-':io n
_-
\/101;<1"';""
" s"st..m IncludCI T••" "i. ....... u..... .. O lfledln .... 48 CfP. 192.3'
"¥' '''--_--'
0".,.,,,,, POll1t
1. Identify HCAs
'-"T"'""'"j
Ch'''lll or 2 10, ooIlon with I'tR >661 n. • OO
Int ..nd ..d lor Hums"
PIC Cool " lnloll 2. or More BUHdfng sllllended lor IIum."
~ < up.ncy'·
Oecupsncy'"
n
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more Buildings
"f>rorMod 8
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_=-,. ,
A5ME & INTEGRITY MANAGEMENT - 'Impact Areas' in A5ME 831.85 •
.,,'1#1( ~
_The refined radius of impact for natural gas is calc ulated using the form ula: = .69 ~ d ,
rooo ft. 660 ft .
.r
" OO ft
• where r is the radius of the impact circle in feet, e o is the pipeline segm ent's maximum allowable ope rating pre ssure (MAOP) in psig, ~",. 1'<;, ",.,..~ ,~.. .....,~
Pipel ine
of I
.t<" ,".
_ d is the outside diameter of the pipeline in inches. _F or exam ple, a 3D-inch diameter pipe with a maximu m allowable operating pressure of 1000 psig, has a potentia l impact radius of approximate ly 66 0-ft: .69 (30 in) (1000 Ib/in2 ) 112 = 654.6 ft '" 660 ft . • r = .69 * d 'i'p
=
GR I-DQI01B9 _ A Mod el f()/ Siting High Consequence Areas Associated wilh Nal u,al Gas Pi pelines
Note that the 0.69 factor IS10.- na tura l gas _ othe r ga se s will ha ve other fact ors
'"
A5ME & INTEGRITY MANAGEMENT: 'Impact Areas' for Consequence Analysis et!I€~, _ The operator counts the number of houses & individual units in building s within the potential impact area. The potential impa ct area extends from the center of the first affecte d circle to the center of the last affected circre _This housing unit count can then be used to help determine the relative cons equences of a rupture of the pipeline segment. _M INIMUM CO NSEQUE NCES TO BE CONS IDERED: e r ocuteuoo density . Proximity of the population to the pipeline (including consideration of manmade or natura l barriers that ma y provide some level of protection) . Proximity of populations with limited or impaired mobi lity [e.q.. hospitals. schools, child-care centers, retirement commun ities, prisons. recreation areas) particularly in unprotected outside areas . Property damage . Environmental damage _ Effects of unignited gas releases _ Security of gas supply (e.g.. impacts resulting from interruption of service) _ Public conv enience and necessity _ Potential for secondary failures
'08
54
A5ME 831.85 & INTEGRITY MANAGEMENT: ~,"."" , = Integrity Management Plan Process Flow Diagram Identify Potential
Pipeline Impa ct
By Threat
Gathering , Rev iewing & Integrating Data
I
I Risk Assessment I
I Evaluate All Threats
t
In line Inspe ct,
Hyorote st .
Ilo'egeityALe"meo,- J
Direct Assessment. Or 'Other'
I Response to Integ rity Asse ssment & Mit igation
O_2OOlI_·'
'"
A5ME & INTEGRITY MANAGEMENT: R is k Assessments
tIM,
_ Objectives: . Prioritization of pipelines/segments for scheduling integrity assessments and mitigating action. • Assessment of the benefits derived from mitigating action. e b eterrnmauon of the most effective mitigation mea sures for the identified threat s. • Assessment of the integrity impact from modified inspection intervals. • Assessment of the use of or need for alternative ins pection methodologies .
_ More effe ctive resource allocation . . RISK
=f(THREATS. CONSEQU ENCES)
'If a man will begin With certamtleS, he wiN end in doubts: but d he will be con tent to begin with doubts, he will end m certainties '.
Francis Bacon (1561· 1626), Advance ment of Leami ng
0 " , " - 2OOlI_'
'"
55
ASME & INTEGRITY MANAGEMENT - Risk Assessments (Threats ' to Pipeline) _ Time Dependent : External Corrosion . Internal Corrosion. Stress Corrosion Cracking _Stabl e : Manufacturing Related Defects (Defective pipe seam , Defective pipe): Welding/Fabrication Related (Defective pipe girth weld, Defective fabrication weld, Wrinkle bend or buckle . Stripped threadslbroken pipe/coupling failure); Equipment (Gasket O-ring failure . Control /Relief equipment malfunction, Seal/pump packing failure . Miscellaneous) _ Tim e Independ ent : Third Partyl Mechanical Damage (Damage inflicted by first , second . or third parties (instantaneousfimmediale failure ), Previously damaged pipe (delayed failure mode), Vandalism): Incorrect Operations( Incorrect operational procedure ; Weather Related and Outside Force (Cold weather, Lightning, Heavy rains or floods , Earth Movements) . (The interactive nature of threats (more than one threat occurring at a section of pipeline at the same time) needs to be considered). o_=..._...:......~
__ _.__"'
" " - _ _ .. _
_ _ ..
~
__
. .~~
_._________
oo.._ ..... _
.. _ _ ,• • _
. _, _ _
ASME & INTEGRITY MANAGEMENT: Assessments
~ _ ._ '
•• _
111 ,
I ntegri ty ,""",,,,,,~
Gfi( )
. Following, and using, the priorities dete rmined by the risk assess ment, the operator shall conduct integrity assessments using: _ in_line inspection, _ pressure testing, _ dIrect asse ssment
•
f.
.M,,":· • •
_
••:~
~
"t
© .......~
e orrect asses sment is an integrity assessment method utilizing a structu red process through which the operator is able to integrate knowledg e of the physical characte ristics and ope rating history of a pipeline system or segment with the results of inspection, exam ination and evaluation in order to determine the integrity. _ External corrosion, e.q. indirect assessment using coat ing survey, followed by excavation and direct measurement . Intemal corrosion, e.g . examinations of low points a other methodologies uz
56
ASME & INTEGRITY MANAGEMENT: Prescriptive Integrity Assessment lntarvats for Corrosion IIm@ Pre scr iptive Inte grity Manag ement Plan for >=50% SMY S lines
Ins pection Technique Int erval years ) Hydrostatic Test ing
In-line Inspection
Direct Assessment
Criteria
5 10 20
Test Pressure to at ieaett.z s limes MAQP Test Pressure to at least 1.39 times MAOP Not allowed
5 10 20
I
Predic ted Fai lure Pressure above 1.z sumes MAQP Pred icted Fai lure Pres sure abov e 1.39 li mes MAOP Not allowe d
I
Maxi mum interval w'hen indicatio ns are exam ined on sampling basis Maxim um interval with a ll indica tions exa mined Not allowed
5 10 20
_ Lines operating at <50% SMYS have different intervals (see ASME 83 1.85 -2001) _ Failure pressure is calculated using ASM E B31G or slmil" , _ JF Kielne r at Prceunetaro P iggmg eo~fe rence , Houston. January 2002 said above is not really applicable 10 mechanical damage in plpel,nes; It is aimed at corrosion, A lso, It is not for fatigue cycled lines - this table is aimed at gas lines that - unlike liquid lines - are not usually pressure cycled. A lso, it is nol intended for use with sec . _ It is guidance, and guidance does not cover everything. If your pipeline ;s not covered by the guidance, it is YOU R respon siba.ty to produce a safe altemat ive.
na
SUMMARY
11'
57
SUMMARY: Integrity/Risk Management in USA • • •
New regulations in USA requi re 'integrity management' of liquid and gas pipelines A major elem ent of this integrity man agem ent is 'risk ana lysi s' and 'risk management' An integ rity or risk managemen t syste m can be constructed using :
--_ ...._ --.
I 0 11
I
.='"
L -_ _- '
•
I
I
INTEGRITY/RISK MANAGEMENT
I
o
-
I API 1160
_
I!Ii(,
I
""'"
1l;;.",
I I
I
ASME B31S
I ;!1 ~~ IIII @,!tl( ,
.._, --
. ,,,... ....""-,,".,,,,,. '"
" ~''' ' ''., ,.
" ",..." , " ", ,,
. .....
The pipeline industry now has methods thai can allow it to des ign and operate their pipelines in a safer and mo re cost -beneficial man ner using 'risk management' .
'"
SUMMARY: Pipeline Integrity M anagement
Gatherin g, R..lewln g
& Integrating Oala
Aud lll"ll
"',.,_t. s..... n~
D i...a As . . u ........
~""-
Pipeline Integ rity Management Syst em/Program
Pipeline Integrity Managem ent Pr og ram/ Plan
'"'"'
58
SUMMARY; Key Elements of ASME B31.8S & API 11 6 0
IThreat (Hazard) Assessment I IRisk Assessment I ~ I'Inspections' I IData Management I 0_2OIl6-.
dell =
117
SUMMARY: Risk Management Systems •
NOTE I!! - It should be emphasised that risk management will not reduce risk to zero - this is an impossible dream. •
Pipe lines will always pose some level of risk - our cha llenge is to control this risk to a reasonable level. Failures will occur, even under the most strict and tho rough risk management programme. • Fo r examp le the Carlsbad failure is thought to have been caused by intern al co rrosion. The failure was in a nat ural gas line (where you wo uld not expect intern al corrosi on to be the ma in failure problem ), and the ca suallieslfatal ities occurred in a 'Class t ' area (re mote. rura l). • A risk assessment of this line and location would probably have shown this to be a highly unlikely event and outcome.
0 _2006_'1
'"
59
CLASS TUTORIAL: 'Prioritisation'
CLASS TUTORIAL: 'Prioritisation' •
We will now perform a 'risk assessment' of 3 pipelines.
c-__---,
RiS;k,--
4
• We are going to use a 'Prioritisation Scheme' •
Pipelines can be 'ortortttseo' to allow us to determine an optimum inspection and maintenance schedu le, identify high risk pipelines , etc ..
•
For these types of qualitative risk assessments. we need
to: • Form expert learn -I will now form these teams .. at random. • Agree structured approach - I will give you a structured approach • Identify risks using pest/present data , but focus o n possible futu re m ishaps - you will do this. • Quantify and rank risks - you will do this •
A fter this. we could: M
Pipeli ne
'"
60
1. THE ELEMENTS OF A PRIORITISATION SCHEME • Identify all potential modes of fa ilure .
~
P,
• Identify and determin e th e conseque nces of failure for...-.lil.. each mode. -...
c,
• Estimate the prob abil ity of failure for each mode .
• Co mbi ne the probability and consequences of fa ilure to estimate the risk. ~ • Rank pipelines within a group in order of risk. ~
'"
2. PIPELINE PRIORITISATION Pipeline Information
Internal Corrosion External Corrosion
Loss of Human life Damage to Property
Fatigue Stress Corrosion Cracking Third Party Damage loss o f Ground SupPOrt Third Party Intervention
,- II ,-
Su sceptibility
Severity
Loss of Service Cost of Fai lure Envi ronmental Effects
I 0 I
""'"
RelativeRisk PRIORITY RATING
nces Of Fal ure
I tza
61
3. SIMPLE QUALITATIVE RISK ASSESSMENTS: Prioritisat ion (Susceptibility and Severity) .Probability of failure depends on 'susceptib ility' & 'severity' . For example, a pipeline pas sing throu gh heavily populated area, is susceptible to third party damage. If it is thin walled, it will resul t in severe dama ge. _ For example, a pipeline with many seam weld defects (e.q. a pipeline that has failed a num ber of times on hydrotest), is susceptible to fatigue , but if the pipeline is not pressure cycled it will not be severe.
Susce ptible
()
)
(~~ Severity
4. SIMPLE QUALITATIVE RISK ASSESSMENTS PRIORITISATlON: Calculation _Relative risk = Probability of failure x Consequence of fa ilure: • Probability of failure = Sum of all (7) failure probabi lities, PI _Ind ividual probab ilities = Susceptibility Factor (S, ) x Severity Factor (S,) = P,
_Consequences of failure = Sum of all (5) consequences = C,
I> P o, ,,,,," 2006 ><",,6; ,
62
5. SIMPLE QUALITATIVE RISK ASSESSMENTS· ' RANKI N G' PARAMETERS: Quantifying Factors
_ Rank probability of external corrosion on a scale of 0 to 100 _ Take into account parameters such as coating type (bare pipe , modern factory coated , etc.). age & quality, C P avai lability & efficiency & type, soi l type.
_ Rank probability of mechanical damage: _ Remote (desert?) pipe to a short length offshore pipe . in busy shipping and fishing channel
_ Etc
tzs
o~~_,
6 . SIM PL E QUALITATIVE RISK ASSESSMENTS· 'RANKING' PARAMETERS: Algorithms
A I
Ty ~
Ia
I
I Coaling
Probability of External Corrosion
I
I I Qua lil)' I I
Ib
CI Age
Ie
II
[(flO'''"')
I
I
I
I
I
I
I
I
1 ,11 " ll cII D I
I Ty", I
I I
0- I
I
I I
I 'II F I
Probability = A(Coating) + B(CP) + C(Soil) Coa ting sco re = a(lypc) + b(quality) + ctagc)
I
So;,
I
I I A.......I.y I I Type I
10-,11 0- 111 0-'110 -'11 0-'11 0-11 I
I
~
G
I
100 max
0 _ _ 2DDII_0I1
63
7. SIMPLE QUALITATIVE RISK ASSESSMENTSL: Worked Example
Score each parameter up to 100 PROBABI LITY
~
=-
FAT~
~- ~Susceptibility Sev erity Tot al
CONSEQU ENCES
10 10 100
=
-
.=
~,
50 10 55 10 2750 100 LO SS Of'
DAMAGE
HUMAN
ro
LIF E
PROPERTY
10
50
0 0 0
=~
~
IHl~ P_TV
101.....
INTE~"'TlON
~
60 25 0 30 25 0 1800 625 0
5375
~O S$ O F
COOT Of'
E NVIRO'lMENTAl.
TOTAL
,,>Me<
FAILU RE
EFFECTS
80
40
5
185
Relative Risk ; 5375 x 185 ; 994,375 C" - 2(U _ '
'"
8. SIMPLE QUALITATIVE RISK ASSESSMENTS -CLASS TUTORIAL . You are ope rating three pipelines: . Pipeline 1 is 20", 0.375", operating at 50% SMYS, offshore _ 35 years old, history of leaks from internal corrosion. It passes through environ mentally-sensitive areas . • Pipeline 2 is gas. 30~ . O .75~ _ Failed at seam welds 5 times on the preservice hydrot est. a p asses through high ly populated areas and operates at 30% SMYS . Heavily pressu re cycled. • Pipeline 3 is gas , 36~ , OS a tape wrapped, operati ng at 72% SMYS. Failed once by cracking nea r a seam weld, but remote from com pressor stations. • Perform a relative risk analysis O __
l'OO6~1
~ Crude oil ...~ 35 years old
128
64
9. SIMPLE QUALITATIVE RISK ASSESSMENTS -CLASS TUTORIAL: More Information PIPFU 'iE I
15 " oar
ll~' m;'
PRODUCT CO ATIMi & CP
Cru d< tar . "' .. ,.
"'M. OK
-". ......,-.kJ,o ..............
SFl'UIITV I....SI'ECTIO" SI'kHllL"-,,a t -\l i"n ""-"CE HtSTOllY
•
fAI LL'R E H iS toRY
H JTLRE:onR.\I lo"
-"-
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CI'
H1.- RITV Of SL1'I'lY
j6", O.7S". wc ld
" "fee " Co., Hi E_I''''Y ' P,pro p)'kno: ('I' ~ rrodc m and OK
e""j
F""VIRO' '>tE" y
P1PFl. IN E)
PIrl'LI SE 1
lO·, O.37S-, wc kled ",om IllSA
PIPE
~-
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Sc>naI _ion> --..I .. paooI
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w in hcprn=
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9. SIMPLE QUALITATIVE RISK ASSESSMENTS CLASS TUTORIAL: More Information lUll '.RIA I.SrU lRlO
eeocccro
DUC ro I
DUcr0 2
DUcr0 3
l lr, O.,\7j "
)6",0.75"
ll .oo.."..,;...
I .r.o. """'Ire
16",0.\ " 10""'",
~/~~ \ IYS
W'
n % S\ IYS
"
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~~ lUIMDIllOSU\U-'I.~IItO
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1'\.'iPt('{l()'\ ok \1l'1lA-' l.lA
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DE \ lA.'lTIo.-.JloIltS lO
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\ '.,
~", ,,,,, _
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Opr RA
-
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.............
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,-
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• or "12%
fac1I.y
&... ~"....
-
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ct.x\.«l and .. U li.
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"""...."", lmbI. to 1"Io>odq
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IS lI llllTO RS
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1"""",,_1>Icd
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I :...
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0 _ 2 0 0 1 11......'
no
65
10. SIMPLE QUALITATIVE RISK ASSESSMENTS· CLASS TUTORIAL· USE PRO FORMA T O DO ASSESSMENT PROBAB IUTY
Susceptibility Se verity Tota l
- .~-
r -
c:J.->
~O l).G
CONSEQUENCES
,~ -
. " rlGlJE
sec
'AAn
~
4 0 00 10 'Iv :J..\'\ i"J
j~o
\ 'l-- (J
l OSS OF
D A MI\G ~
HUMA-.
W
li FE
PROPER TY
\0
,-
1't0
\IJ~
LOSS OF SERVICE
40
Relative risk =
0
T""o ...... 'y
=~
,.... E.RVE.... IQN
~
-/(./.
~
~
0
'0
D
0
o
COST OF
E NVIRONMENTAL
FAILURE
EFFE CTS
).0
rOrAL
~,
\1,l o TO TAL
(0
(~~6 y:.
Iq~
\Ik-:;. t: (glX
C:._1OOlI_'
ta t
1 1 . SIMPLE QUALITATIVE RISK ASSESSMENTS· CLASS TUTORIAL This is a project - appo int a project rnanaqer . he/she must deliver 10 lirne! Appoint a point scorer . not the P Manager.
_Rank your pipelines, and state the highest risk pipeline
r:
'"
66
12. PROFORMAS
-
ro eo eo to u o 0 reo 9tf! n
o
.iaY caJ S60(J
I,,,. . """..,,.
'2' I {, 000" ~
I
18 U 11'
Relative risk = ~
) 60
l-~ - ~ -",,-,
D 'Z
-10
J
- _
'-
I"''''''''''NO'' I
I"" '" I
I
Relative risk =
C Po'"",' 2006 Re,6I1
L t-I ADDITIONAL INFORMATION
67
PROBABILITY •
•
Probab il ity has its origin in the study of gambling and insurance in the 17th century • Probab ility is 'chance' - the chance of an unc ertain event occurring 'Odds ' are the ratios of two probabilities • For example , co nsider the prob ab ility and odds of one of these rectangles being coloured in:
The probability of an impossible event is O. The probabi lity that an event is certain to occur is 1.
• The probabi lity of me colou ring in one of these squares in 'I.. or 25% • The 'odds' of one square being coloured in, is 1:3 or 33% 135
,"
PROBABILITY••• can be useful!
•
• • •
• •
Probability can be usefu l. Here is an example : Your company asks you to l ake a dru g lest
• •
let's assume that, typica lly, 2 in 100 staff are drug users . Let's assum e the drug te st is 99% accurate
You ar e nOI a drug user ,.. but you tes t 'pos itive'. You r employ ment ends : the company stat e they are 99% confident you are a drug use r Is this reasonable? No! They are co nfident tha t the drug test is 99% accurate , an d that is all. Actually, one third of staff identified as drug users are NOT drug users! This means they are only 67% confident of you being a user. See the 'deci sion tree' for an explanation: Staff identified as drug users = 0.98% + 1.98% " 2.96% But 33% (0.98/2,96) are not drug users!
• •
•
• •
."p"",,,,,,, 2IlO6 Ro, 6-'1
Popu lation of emp loyees
Non-drug User:
Drug
User: Pd = 0,02
Po" 0.98 Test
Right (+) P e" 0.9
~;\g
J
c o '" e ~~ s
-\1
\
~
0 0;
Right (+}: P c = 0.99
"
~-
Correcl ; Drug user
Correct: Incorrect '"~ Drug u."r Non-Drug user Non_Drug user
P", ~ ',9 8%
P o =O,02%
P._O.9B%
Prn-97%
''''
68
RISK: Probability and Frequency
.Frequency: e.g., "out of 160 coin tosses, 80 land on heads" .Probabilities: e.g., "50% of the coin tosses land on heads" _These can be misleading ...
RISK: Probability versus Frequency* ••• perception versus reality? aconsroer these probability statements: _The probability that a woman has breast cancer is 0.8%. _If a woman has breast cancer, the probability is 90% that she will have a positive mammogram . _If a woman does not have breast cancer, the probability is 7% that she will still have a posit ive mammogram. _ What is the probability of woman who has a positive mammogram actua lly having breast cancer?
?• _24 Physi cians were asked this question. Only two doctors gav e the correct probabi lity. .? ·G ig...n,,", G" 'Ecologica l i"teJl ~ "" "".p'a'Oon fOff,oquenc.,, ' 10 0 Cumm;"Il' & C e Poo,"", o 2006 Re,6I 1
Allen lEd' ),
.
rho E,."M""
.'" C;C;,7'0""" '" A
oIM"'<1. N"", Y"",· 0 .1"," Un",...;'. P,... , 9-29 .
1996.
E"""'"",'S;m". , . l 00" IN Und• ."."",,') " ,"'" "om N" m. ,oey '0 1O"1l!'t'.
(NJ38
69
r: RISK: Probability versus Frequency••. frequency is easier! _N ow cons ider the same statements (with figures rounded up) as frequencies: _ 8 out of every 1,000 wom en have breast cancer. _ Of these 8 women with breast cancer, 7 will have a positive mammogram . _ Of the remaining 992 wom en without breast cance r, 70 will still have a pos itive mammogram. _I magine a sample of women who have positive mammograms during breast cancer screen ing . How many of these wome n do actually have breast cancer?
•
out of
?
?•
_ 1000 women screened: 7 with cancer have positive mammog rams, 70 without cance r will have positive mammograms. Hence 7 in 77 women with posit ive mammograms w ill actually have cancer (one in 11 or 9%)
r rr nr!Rct c p"",,,,,, .iiicilr "" r answer is 9 out of 100
RISK· THE LAW AND SAFETY AND HEALTH
1<0
70
RISK MANAGEMENT IS ESSENTIAL - UK DISASTERS CAUSE
LOCATION
DATE
FATALITIES
se vern Estuary
-2000
Railw ay
1606 Universal C olliery, Mid· Glamorgan 1913 Brafield Reservoir , 1864 Quinlins Hill, 1915
439 250 227 188
Flood Mine Dam bur st
Fire
Theatre Royal , Exe ter
1887
Oi l pl atform
Piper Alpha
Lan dslid e
Aberfan, Mid-Glamor gan
Explosion
Chilwell, Notti nghamsh ire
1988 1966 1918 1972 1987 19 51 1836 1884
Aircr aft
SEA Trid ent, Staines, Su rrey
Underground
Kings Cross , London
Road
Gillingham , Kent
Snow avalanche lewes, Ea st Sussex Earthquake
Rowhedge
167 144 134 118 34
24 8 1
0_200&_ '
'"
RISK MANAGEMENT IS ESSENTIAL WORLD DISASTERS CAUSE
YEAR
Flood Earthquake
1931 1956 1920 1941 1984
LOCATION Hwang -ho river, China Shensi Province, Ch ina l a nds lide Kansu Province , China Snow avalan che Huaras, Peru
Toxic release Mine Dam burst Explosion
Bhopal, India Uranium, East Germa ny South Fork Dam, Pennsylvania, Halifax, Canada , The Theatre, Canton, China [ Fi relSlllglo ~ ) Aircraft KLM and PanAm 747's Tenerife, Terrorism I~_) World Trade Centre, USA Railway Modane, France Gas pipeline Urals, Russia LPG Storage Mexico City Nuclear _ Slalion Chernobyl
1949 1889 1917
,
DEATHS 3,700,000
830,000 200 ,000
-5,000 2500 1100,000,,,,_"..) 2300 - 3700
2209
1845
1963 1670
1977
579
2001 1917
>3000 543 >500
1989 1984 1985
--.--
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>30 200 ...... _ _ _
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71
RISK· THE LAW AND SAFETY AND HEALTH
.There is international concern over the health and safety of workers and the general publi c, and most countries have laws covering health and safety. e.q.: e o ccupanoner Hea lth and Safety Act (OSHA), 1970 in the USA _ Health and Safety at Work Act, 1974 in the UK
_I n law we have two fundamental principles : a -t . Th e concept of general 'dul y of care' for all persons , i.e . work ers, operators, customers, users, etc.' a 2. Goods and services must be 'fit for purpose' and not result in any dang er to health and safe ty when used for the purpose intended.
'"
RISK· THE LAW AND SAFETY AND HEALTH
(cont.) a1 . In the Europea n Union, we can satisfy 'reasonable care ' when we can demonstrate that the following action s have been carried out: a Risk assessmenl - to identify hazard s and risks to healt h and safe ty _ Reducing the risk to 'as low as reasonably practicable', _ Maintenance to ensu re safety in opera tion an d the provision of inform ation , _ Action to me asure , m onitor and control. _ 2. 'Fitness for Service' is a cont ractua l issue. and subject to civil proceedings . However, if the goods or services effect the hea lth and safety. criminal law may apply. _ For example. a compresso r that breaks down and causes injury may be subject '0 both crimina' and civil proceedings ~
'"
72
EXAMPLE OF RISK ASSESSMENT IN REGULATIONS· UK PIPELINES SAFETY REGULATIONS _ The Pipelines Safety Regulations 1996 came into force in Apr il 1996. _ They replace earlier prescriptive legislation with a more integ rated. goal setting. ris k-bas ed approach that covers both onshore and offshore pipelines . / _The defi nition of 'pipeline' used in the Regulations mea ns that apparatus and works associated with the pipeline (such as compressors, valv es, etc.) also com e under the Regulations . _ The Regulations cont ain a two tier approach: _G eneral duties that are app licable to all pipelines, cove ring des ign , con struction and installation . operation, maint enance and ab andonment . _ Add it ional duties applicable to pipeline carryi ng 'dangerous fluids',
C_200S_'
145
EXAMPLE REGS· UK PIPELINES SAFETY REGULATIONS · THE 'MAPD'
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I PRODUCE SAFETY MANAGEMENT SYSTEM
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73
SUMMARY - CHANGING LEGISLATION
Old Style Leg islation • Prescriptive • Detailed rules and regulati o ns • What mu st be done • Do it anyway
New Sty le Legislation
IL
.., ~
• Risk b ased • Framework rules with guidelines • How it m ust be man aged • Identify hazard s and ri sk s first, then rank th em and prioritise actions accordingly
Risk Management (insurance)
Penspen Integrity
148
74
RISK MANAGEMENT· Past •
The tool used by organisations to ensure business and shareholder value is 'risk
manaqemenr.' •
•
'the process enabling the systematic identification, analysis and managemen t of critical business risks '
Many energy organisations focus on the "hazard' risks only • This is achie ved by tran sferring the risk of physical asset loss or damage 10 a nat ional or international insurer.
•
Insu rers have traditiona lly welcomed this type of business. Why? • Oil and gas assets have been good qua lity over past 20 years
• Were many insurers in the market looking for business in this type of risk . •
This has changed ...
• Age ing infrastructure is failing • $500 ,000 ,000 of insured physi cal losses in Middl e Ea st in 200 1 and 2002 mainly due 10 ageing assets .
•
International reinsurance mark et has reduced from $4b illion capaci ty to
C_:IOO!_, S1billion to absorb globa l energ y risk
,,,
I ...... -~'_'''_.- _ _
RISK MANAGEMENT· Future •
Recent catastrophi c energy inciden ts hav e resulted in global insured ene rgy claims exceed ing globa l pre miums by 100%
•
Insurers will now only accept 'high qual ity' risks
• Severa l incidents have been attribu ted to ageing infrastructure • Ene rgy com panies now nee d to use independent risk engineering report s or ass et valuations to manage this process • Howe ver . do we need to insure aga inst every risk? •
Energy companies now need to assess all risks , and provide an optim um balance between risk retention (they ca rry this risk and cost) and risk tran sfer (to the insu rance mark et). Don 't 'over-insure'. • This requi res an assessment of ALL business risks: • BUSIN ESS· Operational , strategic and financi al • HAZARDS · Hazards such as fire , explosions and natural peri ls
•
W e do this by using consistent risk processes in a co mpany • Identify Risks; Analyse/Mea sure Risks ; Design Aga inst Risks; Implem ent Plans
O_:IOO!_1to Reoucezeummate Risk s; Measure Succe ss and Improvements.
'-..-------
150
75
AN OVERVIEW OF RISK MANAGEMENT
'"
RISK ASSESSMENTS· WHY? Risk Assessments are needed for : • Compliance with regulators , legislation and code (move from prescriptive to goa l-based design). • Con trol of the hazards associated with pipelines (cost of a fa ilure is made up of direct cos ts (e.g. repa irs) , and indirect cos ts (loss of business and goodwill, compens ation claims , etc .)). • Indirect costs ca n be the largest.
• Control of Insurance Cost. • Improvements to pipeline efficiency, safety and security.
' 52
76
RISK MANAGEMENT · WHY?
I_
F a t ali tie s 0 Injuries
30 ,,-25
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RISK MANAGEMENT (definition f rom US OPS) .Safety e'the protec tio n of the pub lic, the environme nt and pro pert y'. • Risk . 'any th reat to ac hieving those goals' . • Risk management e'a ... management decision support process . implemented as a program , integrated through defined roles and responsibilities into the day-to-day operations, ma intenance. engineering management, and regulatory decis ions of the operator '.
'"
77
RISK MANAGEMENT (definition from US OPS) • It encomp asses both risk analysis and control. • It can improve safety by:
I" L,-::,::O I
• Analys ing the precursor events and causes of potential pipeline incidents.
• Examining both the likelihood and severity of potential pipeline incidents. • Prov ide comp rehensive & integrated means for examining and comparing all risks, and prevention and mitigation measu res. • Provide a structured, easily communicated means of identifying and prioritising pipeline risks and risk reduction measures.
• Establishing and tracking performance measures to ensure safety improvement.
THE MOVE TOWARDS RISK MANAGEM ENT • •
•
USA The USA Reg ulations requ ire risk assessment , and codes (API and ASM E) give g uidance UK Pi pelines Sa fety Reg u lations. • Goal-selting, not prescriptive (the State sets the standards to be achieve d, then industry presents the solutions)
• • •
• Starting point for a 'good' pipeline design and operation is a recognised design code, and good, proven operational practices. • But operators are not limited to these. Cana da has non-mandatory 'Gui delines for Risk Ana lysis of Pipelines in its pipe line code. Australi a (AS 2885 .1) requ ires a risk analys is The Euro pea n Co mmi ss io n is reviewing 'major acci dent" pipelines , and are likely to requ ire operators to have a 'major accident prevention policy' and a 'pipeline management system' that ensures the policy is app lied .
/
GENERIC RISK MANAGEMENT· THE I N G REDIEN T S•.. RISK MANAGEMENT
RISK
RISK CONTR OL
ASSESSMENT
EMERGENCY
EMERGENCY PLA NNING
I-- PROCEDURES
CONSEQUENCES
PROBABILITY OF FAILURE
OF FAILUR E
DEFECTI DAMAGE
DEFECT f
DATA
FREQU ENCY
I FAILURE e QUATIONS
DAMAGE
CO NSEQUENCES
OF FAILURES
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79
ADDITIONAL NOTES ON DOT, USA 'FINAL RULE' FOR LIQUID LINES
C_2006_'
159
'FINAL RULE' - 49 CFR 195.452· Background '• •1I~., _A final rule applying to hazardous liquid operators with 500 or more miles of pipeline was issued November 3, 2000, (65 FR 75378). Exte nded to shorter lines in January
2002. _ An amendment to 49 CFR 195.452 in May 200 1 esta blished new requirements on integrity management of liquid pipelines in 'high cons equence areas' (HCAs)
"_2006 _110,
160 ~ ,
80
'FI NAL RULE' - Objectives of OPS _Accelerating the integrity assessment of pipelines in High Consequence Areas _Improving operator integrity management systems
_Improving government's role in reviewing the adequac y of integrity programs and plans , and .Providing increased punllc assurance in pipeline safety.
C_2006_
'"
PERFORMANCE OF L1QUIO PIPELINE OPERATORS _ Liquid pipeline opera tors are inspected/audited against the Final Rule.
_ Audit is lengthy - a number of inspectors over a 2 week period _ Early reports say 80-85% of operators did not comply, with many receiving NOAs and NOPVs (Notice of Amendment and Notice of Possible Violatio n) _ Visit www.promis. rspa.dot.gov
<>_2C06_'
'"
81
ADDITIONAL NOTES ON DOT, USA 'FINAL RULE' FOR GAS LINES
THE COST OF THE NEW INTEGRITY ASSESSMENT RULES' _Northwest Natural Gas Company has agreed with the Public Utility Commission of Oregon to increase its rates by $5m illion. _These costs will be reflected in cus tomer rates _This $5million will cover NW Natural 's increased costs in 2004 from the enhanced integrity program. _These costs will range from $5m il1ion to $15million/annum over the next 9 years
• Pipe"';",.April13 200 4
82
INTEGRITY MANAGEMENT IN TEXAS
165
INTEGRITY MANAGEMENT IN TEXAS
RISK·BASED OR PRESCRIPTIVE _ The Railroad Commission of Texas is responsible for the many 1000 kms of pipel ine s in Texas . _ II has proposed ne w regulation s relati ng to pipeline integr ity assessment and management plans for intrastate natural gas and hazardous liquids pipelines . _ RISK_BASED - The Commission proposed a performance-based option within the rule under which pipe line operators can deve lop an integrity asse ssmen t and testing program thai would identify the risk s associate d with parti cular pipel ine facil ities . - Eadl operator's plan would be recoreo to assess the integrity of specific segments of a pipelin e's sys tem . conside ring all appli cabl e risk factors . e.g . locatiOn. age . croooct, and leak history. - Operators 'NOUId have - 12 months to de-velop thei r asse ssment plans and then another five years 10 do the IfIltlal assessments. a fter wh ich !he operators 'AOU1d develop an ongoing intf!9 nty management plan for managing the identified nsxs. - The Commission 'AOUkI ha ve to review and accept all plans for Inlegnty assessment and management.
• PRES CR IPTIVE - If an o perator chooses not to develo p an assessment progra m, then the operator wo uld be requ ired to use the pre ssure testing or in-line testin g options with 5 and 10 year retest intervals . O_2OOli",• .r,i'
83
TEXAS - RISK·BASED APPROACH _ The risk-based plan must contain at lea st: _ IDENTI FICATIO N of the pipe lines & segments cov ered by the plan _ A PR IORITY RA NKING of the pipe line/segments of each sys tem based on an analysis of risks (see next slide) _ A SSESSMENT OF PIPELINE INT EG RITY using at lea st one of the following m ethods appropriate for each segment: _ in-line inspe ction , e pressurs test . 'direct assessment' (e .q. coat ing inspection), or . other new technology. _ MANAG EM ENT methods for the pipeline segments whi ch may includ e remediation o r increased inspe ct ions as nece ssary; and . PER IODIC REVIE W of the pipeli ne integ rity assessment and m anagement plan every 36 months , or more frequently if necessary.
C_
2OOi_'
'"
TEXAS - RISK-BASED APPROACH
PRIORITY RANKING _T he priority ranking of the pipel ine/ segments of each system mu st tak e into account: a oooureuon density, . the identifi cati on of significant threats to the env ironmen t & publi c health /saf ety, a pipelin e co nfiguration, . prior in-line inspect ion data or report s, . prior pressure test data or reports . • Ieak and incident dat a or rep orts, . operating characteristics such as MAOP). cathodic protection surveys. etc ., a constructron recor ds , including 0 the age of the pipe and the operating history, . pipeline specifications: and . any other data that may assist in the assessment of the integrity of pipel ine seg ments .
",
X4
TEXAS - PRESCRIPTIVE APPROACH LIQUID LINES Hazard ou s Liq uid s requi re a press ure t est or an in -li ne in spection , and rem ed ia l acti o n in accordance w it h t he f ollowing
schedul e;
Pipeline
Schedule
Rural
5 - 10 years' "Depends on liquid carried
0_
Non-R ural
5 years
Crossing of Navigable Waterways
5 years
Offshore
Interva ls prescribed by operator
2005 _',
' 69
TEXAS - PRESCRIPTIVE APPROACH GAS LINES Gas transmission and gathering lines require a pressure test or an i n-li ne inspection , and remedial action in accordance with the following schedule :
Pipeline
Schedule
Onshore
5 - 10 years'
Offshore
Intervals prescribed by operator
"Depe nds on lo cat ion classification, diamet er, st res s and press ure. Class 1 li nes are 10 years , Clas s 2, 3, 4 at >20% SMYS are 5 ye ars .
0_ 2006_11,
' '0
85
RISK ASSESSMENTS IN AUSTRALIA (AS 2885.1)
RISK ASSESSMENTS - SIMPLE APPROACH Australia (AS 2885.1) - Probability Analysis ' Frequen cy ' of occurrence of a Hazardo us Event
OP_ _
Description
•
Freque nt
Expected to occur typicall y once per year or more .
Oc cas ion al
Expected to occu r several times in the life of the pipeline .
Un li k ely
Not likely to occu r within the life of the pipeline. but possible .
Remote
Very unlikely to occu r within the life of the pipeline .
Improba bl e
Examples of this type of event have historically occurred, but not anticipated for the pipe line in this location.
Hypotheti cal
Theoreti cally possib le, but has never occurred on a similar pipeline .
~
R
....,
'"
86
RISK ASSESSMENTS - SIMPLE APPROACH I!ir;A u s t ra l i a (AS 2885.1) - Consequence Analysis Description
'Seve ri ty' Cl ass Cata strop hic
Applicable only in loca tion classes 'T 1 and T2'· where the number of humans within the range of influence of the pipeline would result in many fatalities.
Major
Event causes few fatalities or loss of continuity of supply or maj or environmental damage.
Severe
Event causes hospitallsing injuries or rest riction of supply, or minor environmental damage.
Min or
Event causes no injurie s and no loss of or restriction of supply.
• Suburban, resident ial, commercial, 'high rise ' areas
0_2006_',
'"
RISK ASSESSMENTS - SIMPLE APPROACH Australia (AS 2885.1) - Risk Matrix/Analysis Frequ ency of
Risk Class
occurren ce
Severity Class Catastrophic
Major
Severe
Minor
High
H
H
Intermediate
Occ asio nal
H
H
I
Low
Unlikely
H
H
L
L
Rem ote
H
I
L
L
Improb ab le
H
I
L
Negligible
Hy pot het ic al
I
L
N
N
Frequent
R7
RISK ASSESSMENTS - SIMPLE APPROACH ~ Au stra lia (AS 2885.1) - Risk Management Risk Class
Risk Management Actions
Action Required High
Intermediate
Low Negligible
Modify the hazardous event, the frequenc y or the cons equence to ens ure the risk class is reduced to intermed iate or lower. Repeal risk identification & evaluation processes to verify and , where possible to quantify, the risk estimation. Determ ine the accuracy and uncertainty of the estimation. Where the risk cl ass is confirmed to be intermediate, mod ify the haza rdous event the frequency or the conse quence to ens ure the risk class is reduced to 'Low' or 'Negligible' . Where the risk class cannot be reduced to achieve 'Low' or 'Neg ligible ', act ion shall be ta ken to remove haz ardous events, or reduce frequenc ies or reduce severity or conse quences, so as to reduce the risk to ALARP Determine the management plan for the hazardous eve nt to prevent occurrence and to monitor changes which could affect the class ification. Review at the next Rev iew Interval
H5
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EMERGENCY PROCEDURES & PLANNING
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88
EMERGENCY PROCEDURES L\lr KG E~C '
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OPERATOR A!'lD LOCAL AUTIIOR ITIES ML'ST LIAISE TO t.NSUll t. T1lt.OPERATOWS
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EMERGENCY PLANNING· Example O n R "' Tl l lt
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r: RISK MANAGEMENT: Concluding Comments
"9
S U MMARY · THE WAY AHEAD? •
The preferable way is to produce a 'paper-based' risk management system , but the general approach would be: •
HIGH LEVEL 'SIGN -ON' - Obtain corporate agreement , and exec utive 's ign on' 10 'ntrcduce risk/integrity management systems into your company. • The focus is safety, and all risks and ga ins of all stakeho lders in the proce ss should be cons ide red and documente d
• •
• •
• •
RISK TEAM - Form an expe rt pane l, or hire in expert ise , to produce and manage your risk ma nagement system. Agree on performance measures, accountability, etc .. RISK/IN TEGRITY MANAGEMENT PLAN - Follow the requirements of the Regu lations & guidelines in this presentation, or the API ( 1160) or AS ME (831.8) integrity management documents . MANAGE AND CON TROL AND UPDATE Al l DATA - Al l data you have on you r pipeline is of value in your risk management, and it form s a key 'plat form ' in building up your risk profi les RISK ANALYSIS - Rememb er that we can nev er reduce risk to 'zero'; therefore, we are using risk ana lys is as a too l to identify high risks that need our attention. The risk ana lysis can use software too ls (usua lly called 'applications' ) that will use our database, but this ana lysis is only one part of our risk management. MANAGEMENT SYSTEM - The above plan is incorpo rated into a management system to allow a systematic and performance measured way . KEEP DOING TH INGS BETIER! - Cont inuous ly improve your performance and system , and recognise that risk ma nagement is a commitment to all stakeholders in your pipeline, for the life 0 the pipel ine
90
SUMMARY - 'T OP TO BOTTOM' _ Risk is a partnership in a company: e c orpor ete management enables things 10 be done, as it controls finance and sets objectives and assigns responsibilities
_Designers conceive ideas and turn them into detailed drawings and specifications _ Engineers turn detailed drawings and specifications inlo plan t and equipment e o peratc re and users put plant and equipment to useful purpose _T herefore, risk management starts with co rporate management
_ However risk can only managed if they are reco gnised as a threat and there is a fear of their consequences _ However, many boards and senior managemenllack the imagination of experience to recog nise risk
_ Engineers and operators are closer 10 the risks , and they must learn to educate management in these risks
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SUMMARY· THE FUTURE?
'"
91
~ Responsibilities, Morals and Ethics '" " "
for Engineers
Penspen Integrity
1
OUTLINE Responsibilities
'Professional' Loya lty Conflicts of interest
Ethic s Ethi csfR espo nsibiliti es of Eng ineers
Sta nda rd of Ca re Accident
Reasonable Care Competence Neg lig ence Fitness for purpose
Socio-Eco- Huma n Rights Responsibilities
The legal System Personal and Pipeline Security 2
RESPONSiBILITIES••••
list the top three orga nisations/people you are res po nsibl e for?
.,_2IIlIll-'
3
RESPONSIBILITIES • . We have many responsibilities in OUf lives. They can be: . amily (e.q. care for your children); • social (e.g. ca re for your neighbour); • profe ssional (e.g . ca re for you r clients);
. spiritual (e .g. satisfying our consc ience ); and
. political
(e.g.
care
for
developing
• ... .1
~~
0
!t' Ii.oil 1:w . r=J •
countries ).
-.Ale w ill focus on our responsibilities in this lecture
professional
,
?
RESPONSIBILITIES: Professional .Responsibility usually means we are expected to achieve or maintain a result, as we have the required knowledge
.It does not requ ire 'perfection' .-This is because we may not always ach ieve the result:
-.A responsible physician may see a patient die; -.A responsible
eng ineer may witness design failing in an unforeseen accident
his
5
RESPONSIBILITIES: Staff/Job ~e have responsibilities to all 'stakeholders' who are affected by our work/decisions
.The company we work for .The client we are making the decision for ~ny person/environment affected by our decision
lIThe above leads to five areas (all linked) we need to address reo our eth ics/respons ibilities and duties: .Professional behaviour .Ioyalty - to your profession and company, .conflicts of interest - between you and your company or client .ethics - in dealing with matters of conscience and morality . • duty of care - to all stakeholders in your decision making, e """",,,n ' 006 Rev6l1
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PROFESSIONAUPROFESSIONS
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PROFESSIONAL /PROFESSIONS ' . 100s of years ago , you could be anything : docto r, de ntist, carpenter ... without qua lifications
. 1DOs of years ago , your loca l barber , was also you r dentist, surgeon, etc., because he had scissors and knives!
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PROFESSIONAL: What is i t ? ~hat
is a 'professional'?
. Most people view a 'professional' as someone who receives pay for a job. • In a recent survey of young people , 'movie stars' were included in a list of 'professionals'. ~ window cleaner was recently described as a 'fenestration hyg iene executive'!
. Let us look at the history of 'professional' to help us understand its meaning
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PROFESSIONAL: What is it? .The notion of 'professional' is derived from the idea that peop le professed - promised - to meet high moral standa rds . Traditionally, min istry, med icine and law were the professions. as they requi red extensive training, and the ir practice was exclusive to their group : for example. you could not practice medicine without belonging to their group
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PROFESSIONAL: What is i t ?
. So, now we consider a professional as someone who receives payment for a service, but also... • is a member of an organ ised profess ional body with a ... recognised standard of w conduct. .. U •••
. .... has so me speci al skill or ability or some spec ial qualifications derived from training or experience ..:
PROFESSIONAL: Responsibilities . Our 'Respon sibilities': . professional - the responsibility that arises from a special knowled ge ; . company- these are our 'official' or specified duties in our job;
. Iegal - those required by society.
• We are 'Accountable' to: . the company we work for; . the client we are making the decision for; . any person or environm ent that may be affected by this decision. 0 _ _ 2OOll1l_'
PROFESSIONAL, Staff Responsibilities ~II
these responsibilities and accountabilities lead to three areas we need to address:
.Ioyalty - to your profession and company .ethics - in dealing with matters of conscience and morality
.competence ('duty of care') - to all stakeholders in your decisionmaking Responsibilities are delivered through loyalty And reflected through ethical practice
LOYALTY
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LOYALTY .Loyalty is 'friendship or duty towards something or somebody' .Loyalty is a confusing concept.
-.Ne can see people being 'loyal' to a football team , but to a company? .-To a profession?
.-To a customer?
LOYALTY . Loyalty in a company .Most staff are employed by an organisation . • He/she will have an employment contract and 'Terms & Cond itions' will req uire some 'loyalty', e.g. a long notice period, and a com pany 's rewards package (e.g. large pension) may be seen as warranting some loyalty in return . • Ensuring loyalty by good pensions, company cars, etc ., is a simple buy ing method . • This is similar to supermarkets' 'loyalty' cards because they pay you back for your custom. ~ga in,
a simple financia l deal.
LOYALTY . Loyally differs
rl'Ne have loyalty to family rJIoNe have loyalty to colle agues
. Etc . Consider the different loyalty offered by a cat and a dog ...
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LOYALTY vs COMMITMENT . Loyalty should not be confused w ith commitment.
. Commitment is 'dedication to a cause or principle' . Football fans are both loyal (t hey would never support a rival team), and committed (they w ill turn up to every match 10walch their team eve n if the weath er is bad an d the offering worse),
but... lithe players in their team are only committed . as their loyalty is a function of their financial payments and contractual detail. and can change any day .
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LOYALTY· Company
LOYALTY · Company .what do companies look for in staff in terms of loyalty? ~
new employee who has had 10 jobs in 10 ye ars . may appea r disloya l / '
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8A existing emp loyee who has been with the same :~ '. compan y for 25 years.. . \ _ • may be see n as lac king a mb ition
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~ re view by a USA company reported career advisers as listing 'loyalty' as 10th out of 11 as wha t they thought employers were looking for in new recruits.
. rap of the list was team player . intelligence and professio nal demeanour. . LOYALTY IS CERTAINLY A CAREER ISSUE , BUT IS IT A PROFE SSIONAL ISSUE ? 20
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LOYALTY· Staff -.Ne have a legal definition of loyalty . '... an im plied duty that an employee is to act solely for the benefit of his or he r employers in all ma tter s within the sco pe of em ployment.'
aA. me mber of sta ff mus t make his or her own decisions o n loyalty to a co mpany in terms of his or her car eer prog ression. • However, in our professional work , we do not owe unqualified loyatty to a company, as this w ould be a sacrifice of an employee's aut onom y,
. For example, a maintenance manager who tells a maintenance engi neer to 'watch costs' , is behaving in a reasonable, legitimat e manner, _ but if this manager asks the enginee r to cut costs by neg lecting certain agreed proc edu res, the engi neer is placed in a diffic ult position .
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ENGINEERS AND LOYALTY • The above lega l defin ition of loya lty help s an engineer in these circum stances; if a n ille gal or dangerous act is being proposed. it is not to the benefit of the co mpany . • PR OFESSIONAL CO DE OF ETHI CS - Remember. in ce rtain circu msta nces, a professi onal code of ethics may con tain an ex pression of public policy, and a profess io nal may be expect ed to abi de by this professional code as we ll as fede ra l and stat e law s. " -hat duty may oblige them to decline certain acts requested by an employer. _ E MUST NEVER LET OUR COMPANY OR PERS ONAL LOYALTIES BREAK LEGAL OR ET HICAL BARRIERS
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LOYALTY AND 'COLLEAGUES' • You will form 'friendships' at work . • This may lead you into conflicts: for example if a colleague who has become a 'friend ', asks you to 'cover' up something for him/her .The same applies to customers: 'friendsh ips' can be formed, that may lead to conflicts . • There is nothing wrong with these friendships, but you must divorce your professional life from your social life, whenever a professional/business decision is being made. ~nd
remember... DA colleague helps you move house. DA friend helps you move the body ....
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CONFLICTS OF INTEREST
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CONFLICTS OF I NT EREST .-The previous definitions of loya lty tell us not to act aga inst our compa ny's inte rest , but do they prevent conflicts of interest? .-Typical co nflicts of interest that arise in co mpanies incl ude: . having a finan cial interest such as a sig nifica nt a mount of stoc k in a supplier that could benefit from one's profess ional decis ion s (see below); . hav ing fa mily me mbe rs or business associ ates wh o could benefit from fav ouritism; . having a pos itio n of authority on a public or governmental bod y that might allow one selectively to be nefit business associa te s. one's employer, family members , or one's ow n financial interests; and ......orking for a co mpetitor or for com peting clients at the same time. 25
CONFLICTS OF INTEREST - GUIDANCE FOR STAFF . Most co nflic ts of interest are o bvio us & easi ly avoided, but we have formal gu idan ce . For example many profes sional soc ieties have codes of ethics, which inc ludes conflicts of interest. . Codes of cond uct issued by companies em ploying eng ineer s ma y conta in simi lar wo rds. • Refer to these if you are unsure abou t a co nflict of interest, or refer to ou r line management.
CONFLICTS OF INTEREST - GUIDANCE FOR STAFF . Measures recom mended for dealing with a conflict of interest are: _ avoidance if possi ble (for example, refusing gifts from vendors), _ divestment (for example, selling one' s stoc k in a supplier), . resignation (for exa mple, leaving a public boa rd that often cons iders co ntracts involving your comp any) , .N on-participation (for examp le, removing onese lf from the evaluation of potential subcontractors if a relative is one of the candidates), and _ disclosure of the facts of one's situatio concern ed.
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ETHICS
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ENGINEERING AND ENGINEERS lIThe UK 's Roya l Academy of Engineering has defined 'eng ineering ' and what an engineer does : .'Eng ineering is the kn owledge required , and the process app lied , to conceive, design, make , build, operate , sustain , recycle or reti re, something of sign ificant technical con ten t for a specific purpose; -8 concept, a model, a product, a device, a process, a sys tem. a techno logy, .Engineers are individ uals who app ly this crea tive process.'
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ETHICS: Overview • "Ethics" has at least three senses in English : it can be
.1. Another word for ord inary morality,
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• "Moral ity", refers to those standards of conduct everyone (every rat ional person at his rational bes t) wants every other 10 follow even if eve ryone el se's following them would mean having to follow them too . • Moral ity (in th is sense) is the same (common') for everyo ne, e ngineers included . • 2 . The name for a fie ld of philosophy, or
.3. The name for a set of special (morally permissible) standards (for example, eng ineering eth ics ). • ' Ethi cs' is the conventional term in the U.S . for 'professiona l standards' . • Hence, many professional eng ineeri ng bod ies have detailed eth ical codes (e .g . ASME). <:l Pon. p"" 2000 "",",'1
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ETHICS: Engineering . Enginee ring is an impo rtant and learned profession. -.As mem bers of this profession, engineers are expected to exhibit the highest stand ards of honesty and integrity. -.Additionally, engineers must perform under a standard of professio nal behaviour that requires ad herence to the highest principles of ethical condu ct.
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ENGINEER'S RESPONSIBILITIES/ETH ICS -.Ne can describe profess ional standard s as those "morally perm issible standard s of co nduct each member of some partic ular occupational group want s every other member of the group to follow . even if every one else's follow ing them would mean having to follow them too." • A profession 's ethical standards must be comp atible with our co mmo n morality, but they go beyond our common morality. 1IY0u could say that they interpret ou r common morality for the specific details of work of a particul ar occupation al group . • For example. almost all the engineering code s of ethics in the U.S. include as a provision. "Engineers shall act in professional matters for each employer or c lient as faithful aqents. "
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ENGINEER'S RESPONSIBILITIES/ETHICS (from ASME) THE FUND AMENTAL PRINCIPLES
. Engineers uphold and advance the integrity, honour, and dignity of the Engineering profession by:
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. Using their knowledg e and skill for the enhancemen t of human welfare ;
. Being honest & impartial , & serving with fidelity the public, their employers and clients;
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. Striving to increase the competence and prestige of the engineering profe ssion.
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ENGINEER'S RESPONSIBILITIES/ETHICS: from RAE . TH E UK's Royal Academy of Engineering has four fundamenta l ethical principles: ~ cc ura cy
and Veracity ;
.Honesty and Integrity; . Respect for Life , Law and the Public Good; . Responsible Leadership; Listen ing and Informing.
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ENGINEER'S RESPONSIBILITIES/ETHICS . Professional Engineer' is the term for registered or license d engineer in some cou ntries including the USA and Canada .-The earmark that distinguishes a profe ssiona l engineer is the aut hority to ·sign off" or "stamp" on a design or a structure, thus ta king legal responsibility for it. .-The term 'Professional Engineer 'is a legally protected titre ; the practice of engineering is protected in both Canada and the United Stales, . In some co untries, engineers are prohibited by the Code of Ethics from practi cing beyond their train ing and experience. • Breaches of the Code may be sufficient grounds for suspension or loss of license, as well as financia l pe nalties
. In some countries it could also result in jail time, shou ld 'neglig ence' be shown to have p layed a pa rt in any incident in w h ich there is lo se of hu man life. e_2OOlI_
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ENGINEER'S RESPONSIBILITIES/ETHICS (from ASME) THE FUNDAMENTAL CANONS ('RULES') 1 Engineers shall hold paramount th e safe ty , health and w elf are of t he public ... 2. Engineers sha ll pe rfor m services on ly in areas of the ir co m pete nce . 3 Engineers shall continue their professional development throughout their careers and... provide opportunities for the... developme nt of those engineers under their supervision. 4. Engineers shall act in professional matters for each employer or client ... and shall avoid conflicts of interest. 5. Engineers shall build their professional reputatio n on the merit of their services and shalt not compete unfairly with others. 6. Engineers shall as sociate only with reputab le persons or organisations . 7. Engineers shall issue public statements only in an objective and truthful manner. 8. Engineers shall consider environmental im pact In.. < their professional duties.
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ENGINEER'S RESPONSIBILITIES/ETHICS (from ASME) THE FUNDAMENTAL CANONS ('RULES')
1. Engineers shall hold paramount the safety, health and welfare of the public ... 6. Engineers shall associate only with reputable persons or organisations . 8. Engineers shall consider en vironmental impact in .. their professional duties .
ENGINEER'S RESPONSIBILITIES/ETHICS· Environment .Currently, prof essional engineering societ ies in the US. are beginn ing to respond 10widespread concern about the envi ronment. .Some engineering societ ies have considered whether existing codes already encompass protection of the environment, by way of Canon 1" "Engineers sha ll hold paramount the safety, health , and welfare of the public in the performance of their professiona l duties"
.However, two societ ies have added provisions regarding the environment to thei r codes . • In view of changes such as these, we can speak about an evolving mora lity in the profession, or an evolving ethics (ethics being the conventiona l term in the U.S. for professional standards).
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ENGINEER'S RESPONSIBILITIES/ETHICS ~o u are asked to route a gas pipeline through a village in Africa , and the route violates the A SME 8 31 .8 location classification
_ If you route through the village the operator saves $1,000 ,000 _ If the pipeline is routed through the village, .. the Village chief will be paid $15000 plus an an nual rent for the ROW , plus an annual payment for clearing the ROW . The $15000 will pay for a new schoo l, medica! cen tre, & permanent water supp ly . The annual rent will pay for annual costs and staffing for the sch ool and medical centre .-The annua l paymen t will doub le the size of their goat herd .-The village cannot relocate _ If you re-route around the Village, the village will rece ive nothing _ Your decision?
CORPORATE SOCIAL RESPONSIBILITY (CSR)
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CORPORATE SOCIAL RESPONSIBILITY (CSR) . 'Corporate Socia l Responsibil ity' (CS R) refers to the responsibility that modern business organisations have to creating a healthy and prosp erous society. • Businesses no long er can work in isolation ; e.g.: . he products and services tha t they provide are consum ed by large numbers of consumers, their employees are part of wid er com munities, in which they have responsibilities to fam ilies and other soc ial groupings. • busin ess activity impacts on the lives of people in ma ny ways, ranging from the creation of a safe and clean environment, through clean and carefu l production. to the creatio n of jobs , and opportunities for all mem bers of the commu nity .
CSR: The Change.. • • Gone are the days when the mandates of the oil and gas majors were restricted to comme rcial act ivities . Gone are the days wh en, provided they worked within the laws of the land, they were solely accountab le to their shareholders, with issues such as human right s beyond their remit" . Now, corporations must consi der other stakeholders such as local commu nities. • Responsible businesses are responsible citizens. .-T his responsibility is reflected through ethical practice . • Ethica l practic e invo lves doing the right thing rather than the wrong one - and is based on operating in a 'moral way' . ." """'''''" >006 _
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·O il and Gas Journal, 1999, J Bray, 'Petroleum and Human Rights : The New Frontiers of Debate '
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CSR: What does it involve?
. Corporate social responsibility involves making sure that: . your goods and services meet customer requirements. and are provided in a fair way . lIyour employees are given responsibility and opportunities to work. w ith the organisation in supporting community projects . • he organisation is involved in relevant sponsorship and 'corporate giving' activities that are relevant and help ful to the community. lithe organisation is involved in activities and programmes that support the development of the whole community.
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CORPORATE STANDARD ('DUTY') OF CARE . Pipeline companies and eng ineers are not automatically liable for an accident/eve nt. IIThey must be shown to be 'at fault'
. l awyers look at each case and ascert ain if 'due care' was exercised .
• Four yardsticks apply: • Feder al Regulations (note: these are minimum requireme nts that must be met ): . State Regu lation s (note: States can impose highe r standards than Federal);
Remember : Awareness • Adherence , and Vigilance!
IlAdvisory standards [e.q . ASME or API. but rete that demoostrating that you have met minimum stand ards is not an impregnable defence); . Private knowledge & conduct (companies are expected to adopt best practices . learning from previous accidents . etc ..) O_~_,
ENGINEERS' STANDARD ('DUTY') OF CARE IlAn eng ineer's service need not be perfect; he/she is using judgement gained from learning and experience, and w ill usually be working in an area where there is a certain amount of unknow n/uncontrollable factors. _ Error comes from variab ility and uncertainty , e dealing with human beings
go in
• Error is a fact of life ('to err is human'). - So when one hires an engineer, one accepts the risks of that professi onal making similar mistakes to other normally compete nt eng inee rs.
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ENGINEERS' STANDARD ('DUTY') OF CARE: De fin it ions .-Two definitions of 'S tandard of Ca re': . That level or qu ality of service ordinarily prov ided by other normally co mpetent practitioners of good standi ng in that field, contemporan eously provi ding similar servic es in the same locality and under the ~~51~"" sa me circumstanc es . • .... that which is com mon ly possessed by members of that professio n or trade o n good standi ng. It is not that of the most high ly skilled. nor is it that of the aver age member of the profession or trade , since those who have less than med ian or average ski ll ma y still be co mpetent and qualified .. .'
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ENGINEERS' STANDARD ('DUTY') OF CARE ·
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Liability IlAn engi nee r is not liable for damages for every error . however, if the error is wor se than a certain leve l, he/she is liable.
. The line between negligent and non-negligent is the 'standard of care'.
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ENGINEERS' STANDARD ('DUTY') OF CARE · Failure ~
judge or jury will decid e on this standa rd of care after hearing expert testimony. • The expert witness assesses against a normally competent engineer, not expert. Failing a standard of ca re wou ld be by:
. not having learning and skill ordinarily possessed by other engineers . • nol using the same level of skill,
. not using reason able diligence and best judgem ent . failing to accomp lish the purpose for which th e enginee r was employed
. In the USA 'reaso nable care' is"... 'the amount of care that a reasonabl y prudent person would use in simi lar circumstances' , • If an engineer does not exercise 'reasonable care' they may face prosecution. C: _ _
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ENGINEER'S STANDARD ('DUTY') OF CARE· Defence . Conversely, a comp any/engineer can show they were taking 'due care' before any incident by* ; . adherence to federal and state regulations; . conforming with advisory standards; . private know ledge and conduct.
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ENGINEERS' STANDARD ('DUTY') OF CARE: Variations lIThe standa rd of care varies with time , locale and circumstances , . Calculations are not in themselves engineeri ng... but they do convey the thought process and desi gn inten t. The qua lity, etc. of ca lculations indicates the level of care and diligen ce; calculations substantiate , but do not substitute for j udgement.
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.-The use of canned ca lculation s and design approaches wit hout und erstanding their a pplica tion & limitations, is beneath a standard of care ,
. 'Low bidde rs and "can-do" type of guys kill people' . Engineers have a duty to warn all parties of any imminent da nger, even if the client feels it is not approp riate
. Engineers must report safety issues , even if it is not in their spec ific remit. ___
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ENGINEERS' STANDARD ('DUTY') OF CARE: In t h e past••• • Eng inee rs have always been responsible for their work, and their failures .. • For examp le, 3000 years ago, Hammur abi the great est ruler (1795- 1750) of Babylon , produced a remarkable list of cod es and laws for his peop le. • It is the earliest complete legal code know n .-They were eng raved in 2.4m high blocks of granite . One of these laws was ... 'If a builder builds a house for some one, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death '.
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ENGINEERS' STANDARD ('DUTY') OF CARE: USA IlAny major incident involving critical private infrastructure will be the subject of close law enforcement scrut iny. • For pipelines these agencies are: . FBI, US Environmental Protection Agency , DOT , US Coast Gua rd aThese agenci es will con sider any incidents ca using
environmental damage or injuries as criminal cases IIAn incid ent would be considered a crim e if this 'harm' was linked 10 'culpable conduct' . .-The following evid ence would sho w 'culpable cond uct": . HistOl'Y 01repea t violation s
.:>elibera te behaviou r IlEfforts to conce al .-Tampering with monitoring devices a.\ctivities such as false statements. obstruction , etc.
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ENGINEERS' STANDARD ('DUTY') OF CARE: USA (cont.) . Companies would face c harges after the , prosecu tors have considered : . Was the offence serious (e.q. great harm)? . Were wrong doings common in the company and corporate? .was management was aware of this? _ Is there is a history of offences?
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In the USA a corporation can be charged wilh wrong doings - and the exec utives can be liable
_ Did the company quickly identify and report the incident and respond to it effectively? _ Has the company a 'compliance prog ram ' in place , and is it being applied diligent ly (e.q . we re wrong doers q uickly disciplined )?
This is because corporatio ns act thro ug h the actions of individuals. Therefore , indi viduals can be liable 10 prosecution" ",""""
.would innocent sha reholders or employees suffe r disproportionately?
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ACCIDENT, COMPETENCE, NEGLIGENCE, FITNESS FOR PURPOSE
ENGINEERS AND FAILURES ' . Prior to 1907, engi neers in North Ame rica disco unted the possibi lity of being blamed for any accident through negligen ce, as engineers, by definition, could not be negligent . The Quebec Bridge collapse in 1907 (where the chief engineer was eventually blamed) ended this argum ent. IlAlso, prior to 1950, courts routinely den ied liability of eng ineers and architects 10 anyone injured at a con struct ion site by arguing that the eng ineers had a contract with owners, not construction crews nor users of the structures. • But in the USA in the 1950 s there were cases against builders by 'third parties' who successfully proved liability. • Engineers are now liable for their mist akes ... .
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r ACCIDENTS HAPPEN: Are engineers to blame? .Engineers are often blamed for accidents . • The term 'accident' implies that even where an engineer is at fault, there is no maliciousness on the part of the engineer.
.It is not easy to prevent fa ilures .. . • The Twin Towers in New York collapsed after they were hit by aircraft in 2001. There was some criticism of their design .
• John Seabrook in his New York Times article follow ing the September 11 2001 attacks said 'Engineers can't be asked to make every building safe from every possible event , yet that is just what the people expect, and the engineers try to meet these impossibfe
expectations. '
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ACCIDENTS HAPPEN: Type-? .Fteddermann* describes 3 types of accident : .Engineered: where a design fault has caused a failure; for example the DC-10 crashes in the 1970s and 80s. Clearly, an eng ineer's responsibil ity; .Procedural: resulting from misuse of a product; for example pilot error causing a crash; .Systematic: resulting from a comb ination of errors, where a single one of these errors would not alone cause the accident. Engineer's would have a respons ibility for this type of accident as he/she should consider the interaction of errors, and the ir consequences.
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ACCIDENTS HAPPEN? -.Accidents happen... . • Many 'accidents' shou ld not be described as 'acci dents' • If an 'accident' has preventable causes, it may beco me a criminal
case! ~ n d the fact that the engineers involved in the 'accident' did not inlen d an accident to occur , is not a
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In the Olympic pipeline failure case in the USA, the judge acknowledged that the manager of the pipeline did not intend the failure to occu r, and had good intentions.
However, the j udge sent the manager to prison. 'to pul closure to the matter in whi ch th ree people died' , . 11 is a question of 'reasonable care·L_~~~~~ mj:C~f~ defense!
. Was it an 'acc ident waiting to happen'? - did the engineers exercis e
'reasonable care'?
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'COMPETENCE' . We often hear that an engineer needs to be 'competent'
. A definition from a pipeline organisation* is: . 'A Compe tent Person should have pract ical and theoretical knowledge as well as sufficie nt experience of the particular machinery, plant or procedure involved to enable them to identify defects or weaknesses. and to assess their importance in relation to strengths and functions of the machinery'
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'NEGLIGENCE' . 'Negligence' is":
.-when an engineer's conduct is below the standard established by the laws of a land. for the protection of others against 'unreasonable' risks of harm, and is also h hen we have fully consid ered the possible consequences of our actions, but then failed to act 'reasonably' to avoid the risk of harm to others .
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'NEGLIGENCE' . You may be acc used of 'negligence' in any profession . You can be called 'negligent' if: ~
duty of car e existed between parties
. The defendant breached the dul y ~s
a result of that breach the Claimant sustained damage
_ To avoid being negligent an eng ineer must show thai he/ she has made all the 'prepa ratio ns' thai a reasonable man/woman in this position would recognise to preven t unreasonable risk. This 'duly of care ' can be de monstrated before any incident by:
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lladherence to federal and state regula tioos; ~forming
with advisory standards:
. private knO'N1edge and conduct .
• In all civil cases the claimant is requi red to prove his or her case on the 'balance of probabi lities' . Thls simply mea ns a Judge has 10 be persuaded tnat the claimants version of events is ffiOfe likely to be INe than the defenda nts
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'FITNESS FOR PURPOSE' - Legal implications . Engineers will often use the term 'fitness for purpose'. _ This has several mea nings , and - unfortunately - it has legal signifICance also!
. 1. Consultants working on a structure that - for example - may have a defect in will define fitness for purpose as 'w hen a particular structure is cons idered to be adequate for its purpose, provided the conditions to reach failure are not reached (BS 7910)' . • In this meaning we are adopti ng a techni cal defini tion , but 'fi tness for pur pose ' may have a lega l and contractual meaning in your country.
• For example. in the UK, a consultant engineer is expected to exercise 'reasonable skill and ca re' in his/her work;
. 2 . A contra ctor carrying out a construct ion has a fundamentally different obligation . he/she is obliged by law to warrant (guarantee) that the completed works will be fit for their intended purpose. • This will be implied in his/her contract - it does not have 10 be staled explicitly 6J
'FITNESS FOR PURPOSE' - Legal implications . Ther efor e, a design en gi neer wou ld be expected to exercise reasonable ca re a nd lake due accou nt of both: . his/her Client's requirements and . the purposes of which the installation (e.g. a pipeline) that he/she is designing is to be used. _ BUT the design is not expected to be perfect in law, as there may be some circumstances, unforeseen by the engineer, Ihal causes failure . How ever, if you give a warra nty of 'fitness for purpose', it is equivalent to saying the de sign is perfect ~efences
removed.
",_2001I-'
that would ordinarily be available to the consulting engineer are
'FITNESS FOR PURPOSE' .-Therefore, jf a consultant gives a wa rranty for fitness for purpose (on the completed wo rks) and they are not, he/she wi ll be liable eve n if he/she has used all reasonab le skill and care . lIThe damages thaI ca n flow from a breach of warranty are different from those of negligence: h
arra nty - costs of making the wor ks lit for purpo se,
. negligence - you pay for anything that could have reasonably been
foreseeable. • Engineers should chec k with their professional indemnity insu rance what is covered as a company/profe ssional? Usually , profe ssionals/consultants are not cove red for warranties.
C_2006-.
65
r:
BE PREPARED" . You can prepare (including training) for an incident:
_ Understand possible key litigation issues (for example , know all government department who you must notify in the eve nt of an incident); . Have a media strategy (e.g. have staff trained in dealing with media attention, and not making sweeping, insensitive, flippant or damagi ng statements immediately after an incident) ; . Have procedures to preserve physical evidence at the scene of an incident (after making the incident scene safe, protect and record all possible evidence); . Have procedures to deal with government investigators (e.q . identify a single point of contact in your company); . Develop a policy and procedure for damage claims ( (for examp le. pay for local hospital bills ) . Gel the facts before they're lost (interview staff quickly, etc.) ",_:;>001I_' "
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SOCIO·ECO·HUMAN RIGHTS RESPONSIBILITIES
OUR WORKSocio-Eco-Human Rights Responsibilities
.Our work can take us all over the world. Some times we have to balance social, economic, ecological and business issues/needs: .-Ne mig ht work forlin count ries that have a history of socia listic econom ic support but need our skills/in vestment IIThese countries then are uncomfortable when faced with the high profits required to undert ake the investment risk
68
14
r: THE OIL AND GAS MAJORSSocio~Eco-HumanRights Responsibilities . Governments can accuse oil and gas majors of 'stealing' natural resources . Governments officials gain political credibility by claimin q foreigners are 'stealing' the resources. but are ignorant of investment risk
-ail and gas majors can also be faced with respected pressur e groups whos e sole concern may be in e.g. a sing le feature of the local eco-system, based on mistrust of a multi-nation al. rather than a balanced overview . However, all our companies are bound by law s, moralities, etc., and many have developed Ethical Codes (see , e.g. Shell web site)
C_:lOO6_ 69
THE OIL AND GAS MAJORS Socio-Eco-Human Rights Responsibilities . Ois pro po rtio nate Power : _ The largest oil compa ny in the world - Exxonhad (1996) annua l profits four times the budget of Came roon and 40 times the budget of Chad . • Ethics o f the Majors . 1982 to 1992 Shell's subsid iary in Nigeria spilled - 1.6 million gallons of oil in Niger Delta, most from leaking pipelines , ca using water pollution and de ath of fish, mang roves & tropica l forests . In 1997 the Wa ll Street Journal reported Exxon's chairma n as advising to deve loping countries to avoid env ironmental controls otherwis e they wou ld lose foreign investment.
C_OlOO5_
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PIPELINES Socio ~Eco-Human
Rights Responsibilities
8 So cial & En vi ronmental Con cerns: "_I
. Pipelines can run thro' important ecological
areas . Ind ustrial deve lopments in previously rural environments can lead to work, tradition, socia l and hea lth changes
~F~i;:;:;;:;J!!j
. Po li t ical ln stab ili ty and Human Rights Violat ions : . Pipelines can be laid in politica lly unsta ble or corr upt areas . Wea lth created can lead to sustained instability, etc ., and increased chance of sabotage , env ironm enta l disasters, etc . 8 Revenue generated by governments from pipe lines are not gua ranteed 10 be used 10 al leviate poverty , etc __They may be used for military purposes '" P o",,"" 2000 R.,"", '
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Millions of peopl e with n o electricit y
Mill ions of people relying on biomass
HOW TO BALANCE SOCIAL RESPONSIBILITIES . In all projects we must balance: . Business issues, with, . Social responsibilities.
• So, staff on a project must carefully consider: ~_.,...;;;: . Political, . Environment, . Social, as well as lITechnolog ical.
• This means we have to consider interests beyond those of the investors or equipment suppliers . • Then staff deci de on participating .. ..
Conclusions... Company Checklist c Are you work ing for a company that gives good, fair value? I Do they try and squeeze the biggest profit, and look for gullible customers? I Do they have an ethics policy, and work to it? r Does the company apply its ethics policy globally , or selectively? [ Does the company address all eth ical issues, including controversial issues that may reflect badly on its own image? I Does the company appreciate the wide responsibilities it has to all its stakeholders, and allow open debate about these responsibilities? I Does the company recogn ise the consequences of the use of its products , and address any damaging effects? r Does the company actively pursue solutions to ethical problems; for example, does an oil and gas major contribute to reducing climate change, and ensure profits are spread to all stakeholders, however distant?
Conclus ions.. . Pers onal Ch e c kl ist r lis 'safety' a prime focus for the company, and a clear business goal? L Ooes the company recogn ise its responsib ilities to the environment? r pces the company's 'human welfare' consideration extend beyond its staff, to all other stakeholders? Does the company deal w ith reputable organ isations and governments? I Does your line management act in a professional manner, and consider and challenge company policies if they are unfair, short-sighted, or unethica l? I Does management recogn ise mistakes , both at management level and corporate level? r Do you admire your bosses and colleagues for human values suc h as honesty , mentoring , intellect , hard work, wisdom, friendliness, fairness, etc., or is the only admiration in their position and salary?
r: PRESSURE GROUPS · Example .-The National Pipeline Reform coeuuon is a USA netwo rk of environ menta l and safety organizations, loca l governments, and labour unions formed to protect the environmen t. & public from releases from pipelines IITheir repo rt found thai 'many, if nor most, of the more than 400 deaths and nearly 4,000 injuries incu rred in tens of thou sands of accidents in volving interstat e pipelines since 1984 could have been prevented if : Pi""'''' ' raved'" _ _ ,... ".s IIag;og and corroding pipes had been inspected and replaced regu larly, and: ~f the
federal government's pipeline regulatory agency, the Office of Pipeline Safety, had not been indi fferent to its responsibilities of implementing and enforcing pipeline safety requirements '. ~e
might agree or disagree with Ihese Groups, but we must listen 10 them .
-.. - _.'
- --
IT
Personal and Pipeline Security
Phil Hopkins Penspen Integrity
78
1q
SECURITY FOLLOWING SEPTEMBER 112001 Terrorism a 'rerrortsm is now a real threat to the oil and gas business
INTERNATI ONAL ATTACKS BY RE GION - 1 9 9 8 -2 0 0 3
_ We should neve r be complacent e remember that terrorists attacked the Wo rld Trade Centre in 1993, and
-- "" "" _ =~"7 = "", ~ -,
. Algerian Armed Islamic Group terrorists attempted to fly a jet into the Eiffel Tower in
1994
SECURITY FOLLOWING SEPTEMBER 11 2001 Terrorists a 'Tnere are 3 typ es of te rrorists 'mio osets':
INT E~NATIONAl-
. PSYCHOLOG ICA L te rrorists who are motivated by persona l dissat isfaction & can not diffe rentia te between right & wrong , do not recognise any views other than the ir ow n, & will show no me rcy o r remo rse _ CULT URE MOTIVATED terrorists who are dedicated to a religion, race or na tionality and are aggressive to any perceived th reat to the ir culture; their attacks may incl ude self-annihilation in pursuit of an unq uestioning adhe rence to dogma or propaganda
CAS UA l- T IES B Y
199 6-2003
_ RAT IONAL terro rists who perform a type of cos t ben efit on th eir attacks to determine maximu m impact versus minimum pe rso na l risk
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SECURITY FOLLOWING SEPTEMBER 11 2001 Travel to High Risk Areas _ If you ar e trave lling abroad , re me mber that terrorists can be motivated by many things : _ religion or patriotic ferv our, e nvironment , concern, or animals, elc. _ T herefore . unde rstand the country you ar e visiti ng , and obtai n the late st security information
(e.g. v'
).
_ And re mem ber - as secu rity is increased at officia l/go vernmenUo bv io us locations , the terrorist will strike at 'softer' tar gets. • Plu s ... kidnapping is a $1b il1ion/year business , a nd increasi ng - don't get caug ht ....
SECURITY FOLLOWING SEPTEMBER 11 2001 Travel to High Risk Areas _ ALW A YS co nduct a risk asse ssment of any trave l to high risk areas _ Most secu rity problems ar e failure s of manage men t, therefore ensure secu rity is in place TO YOUR SA TIS FAC TIO N before ve nturing to high risk areas.
IYour life r:
your responsibility
I
82
4'
SECURITY FOLLOWING SEPTEMBER 11 2001 Travel to High Risk Areas - quick tips e c onc uct thorough risk assessment of area to be visited _ Have trave l and hea lth insurance
a t eave a copy of your itinerary w ith colleagues/family _ Make 2 copies of your passport identification page, airline tickets , driver's lice nse and cred it ca rds a t eave one photocopy of this data with colleagues/fami ly at home . Pack the other in a place separate from where you carry your valuables
. Travel light - less to lose , and less to put down when waiting _ Travel on one -stop flights (most accidents are on take offll anding) _ Minimise you r time is public areas of airports - move qu ickly to behind secu rity
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SECURITY FOLLOWING SEPTEMBER 11 2001 Travel to High Risk Areas - quick tips - Do not hire 'flashy' cars (obvious target) . Keep car locked at all l imes _ Don't d rive at night
_ If somebody wants your atte ntion, flags you dow n - ignore himrh er! _ If somebody 'sus pidous' is near your car - do not get out!
_ Dress conservatively - don 't look like a tourist don 't look like a business person - no flash jewellery! _ Store passports, credit ca rds in hotel safe - if you need to carry then conceal them , DON 'T put in 'easy grad ' handbags, outside poc kets, etc.
I
....
-- _....
.
SECURITY FOLLOWING SEPT EM B ER 11 2001 Travel to High Risk Areas - quick tips _ Stay is good hotels (for sec urity) and stay in on floo rs 2-5 (difficult to enter illegally, easily reached by fire services) _R ead the fire safety instructio ns in your hotel room. Memorise the fire escape route
a use busy streets/roads. Trust no strang er. Do not walk alone at night
_I f confro nted - don 't fig ht - g ive all you r va luables - they can be rep laced!
85
SECURITY FOLLOWING SEPTEMBER 1 1 2 0 0 1 Pipelines - General Security _ Mosl pipeline compan ies in USA participate in several alert systems, and co-ordinate throug h govern ment bodi es to learn of any potentia l terrorist activity. a c omoantes rehearse, review and refi ne thei r security measures on an on-going basis. Safely and reliability always have been at the hea rt of everything pipe line companies do.
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coPeo, pe, 2006 Rov6/'
SECURITY FOLLOWING SEPTEMBER 11 2001 Pipelines - General Security _ A pipeline is mon itored all day, every day . A pipeline's flow and pressu re are monitored and regulated arou nd the clock. e c ompanes can deploy extra mea sures . _ This may involve call ing up additional manpower or sophisticated technology. _ The tools used to prepare and respond will vary from comp any to company .
_Emergency response plans will be in place, as they will be required by local laws/regulations. _ Ensure your crisis management plans in not ju st for a shelf - it must be a realistic living document
--
..... ...,
SECURITY FOLLOWING SEPTEMBER 11 2001 Pipelines. Specific _Actions: efdentify process fo r assessing pipeline system and faci lity vulnerabilities - Devetop uniform definitions of secu rity cond itions . Develop graduated set of countermeasures for each security condition level _ Q u ic k M e as ure s : _ limited access to pipeline mapslinformation _ Identify key facilities and secure _ Background checks for selected state and pipeline personnel _ Security exercise program _ Plan rapid restoration of pipeline service following an attack/sabotage . _ S o me USA pipeline companies a re : _ Controlling access, Using intrusion detection, Revie'Ning electronic systems against cyoer-terronsm. Preplanning with FBI/military, Hiring armed guards _Fu tu re : . Govem ment/lndustry partn ership to address security needs . Already started.
44
Pipeline Engineers: Ethics, Responsibilities, and Competency Phil Hopkins Penspen Ltd., UK
© Penspen 2007
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PIPE LINE ENGINEERS : ETHICS , RESPONSIBILITIES, AND COMPETENCY Hopkins, p l
ABSTRACT In recent years the pipeline business has been closely scrutinising pipeline 'integ rity': we expect our pipelines to be safe, and consequently requi re them to have high levels of integ rity. 'Integrity' has various definitions, ranging from 'moral soundness' to 'the state of being entire or complete'. The latter definition is appropriate to pipelines , but the former is appropriate to pipeline engineers. This leads to the question... how do we ensure that our engineer has high levels of integrity? All professions have responsibilities, and the engineeri ng profession is no different: it has responsibilities , and is bound by codes of ethics .
This paper discusses the ethics and moralities of the engineering profession. These are important issues to engineers; their work will take them to regions of the world where there is social injustice, the profits from the oil and gas may not find their way to the people, and where protecting peoples' cultures and their environment is the major consideration. Also, engineers will need to come to terms with the high profits made by the oil and gas businesses, and the fact that much of these profits come from the developing world, and an energy-type that is creating global warming. The paper is intended as a simple ethical guide to all engineers working in the oil and gas business.
1 Technical Director, Penspen Integrity, Hawthorn Suite, Units 7·8 , St Peter's Wharf, St Peter's Basin , Newcastle upon Tyne NE6 H Z, UK. Tel. 44 (0) 191 2382202 . email p.hopki [email protected]. This paper is an update of the paper presented at WT1A International Pipeline Integrity Conference Wollongong, Aust ralia. Welding Technology Institute of Australia . 7-9 March 2005 . It is also based on the author's Keynote Address to the International Pipeline Conference 2006, Calgary, Canada .
© Penspen 2007
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1.
INTRODUCTION
In recent years the pipeline business has been closel y scrutinising pipeline 'integrity': we expec t our pipelines to be safe , and consequently requi re them to have high levels of integrity. Some definitions of 'integrity' are: 'soundness'; 'the state of being unimpaired '; 'the quality or condition of being whole or undivided '; 'completeness', These are all highly appropriate defini tions of integrity for pipelines. and we ensure a pipeline has this integrity by using enginee ring codes of practice , and recognised procedures to both design and operate the pipeline. Another definition of 'integrity' is more personal : 'steadfast adherence to a strict mora l or ethical code' , This leads to the question ... how do we ensure that our pipeline engineer has integri ty? This paper addresses the ethics and responsibilities of an eng ineer that should ensure that he or she has the same high level of 'integrity' as a pipeline!
1.1 Work .. .. We all have to work for money. Some of us are lucky: we also do a jo b we enjoy. The luckiest people are those that both enjoy their jobs, and know their jo bs contribute to social welfare. The oil and gas business is a big, international business: Exxon Mobil, the world's largest publicly quoted oil and gas firm, made $US25billion profit in 2004. These earnings are approximately equal to the gross domestic produc t (GOP) of Luxembourg or Guatemala , and higher than the individual GOPs of Syria, Bulgaria and Kenya. In 2004 , Shell recorded the biggest profits ever by a British company. The $US18biliion earned in 2004 from oil and gas $2million an hour - is equal to nearly 1% of Britain's GOP! 2005 has seen even bigger profits:
Company
Revenu e (S1000m )
Profits (S1000m)
ExxonMobil
370
36
Shell
307
23
BP
253
19
ChevronTexaco
153
14
Total
152
14
Conoco Phillips
198
14
Tabl e 1. Revenues and Profits of the Oil and Gas Majors It is if interest to cons ider the true cost of oil and gas. If we were to consi der the (climate) damaging aspects of fossil fuels we would need to 'tax' these oil and gas majors' profits. We can do this: in Europe, industries (e.g. fossil fuel-burning power stations) are charged a 'carbon tax', related to the amount of carbon dioxide the industry is responsible for. If we were to apply this tax to the above profits, they would turn into deficits! For example, the +$ 19 billion profits of BP would drop to -$31 billion ;Iosses! People wo rking in this business may be exposed to ethical and professional situations where they have to make decisions, not based on the good of the company, but on their personal beliefs and socia l responsibilities .
2 This paper is the final paper in a series of four papers (see also Refe rences 1,2,21) that has add ressed change and ethical issues in the pipeline business.
© Penspen 2007
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This paper covers our responsibilities in engineering , and hopefully will show that money isn't everything , and an engineer cannot be bought! We are going to talk about ethics, and this is highly relevant to pipeline engineers. For example, we may work for companies with interests in Nigeria, or, like the author of this paper, have worked on projects in Nigeria. Nigeria is an 'oil-rich' country but its people are very poor: its population of 130,000,000 have an average salary of $lIday. Its government is striving to eliminate corruption which affects the redistribution of the oil revenues of over $25 billion/year. Should we work for companies with interests in Nigeria? A perspective on the problem was given by the Nigerian Finance Minister when she was interviewed on SBC Radio 4 on 14th January 2005. She said that if all the oil revenue was given to the people, they would only receive an extra $O.5/week. This can be viewed in two ways: •
a $0.5/day increase in salary is negligible by world standards , and would not remove poverty from Nigeria;
•
a $0.5/day increase in salary is a 50% increase for that person, and would significantly increase their quality of life.
Is corruption the problem causing poverty in Nigeria? Is the oil business contributing to Nigeria's problems or alleviating them? Is the oil business, and the profits going to the government and the oil majors, the problem? Also, we will be working in countries, or working on oil from countries that may not be democratic, or may not have good human rights records. For example, the fifteen countries which have oil reserves in excess of 10 billion barrels are: Engineers faced with projects in such countries need to carefully consider all morality, safety and environmental aspects before agreeing to participate.
1.2 Wh at is ' Engineering '? There is little point in talking about ethics in engineering without first understanding what 'engineering'is! Engineering means 'skilled' or 'creative'. Engineers have to research, design, build and operate machines, structures, etc., that will function safely and efficiently. Engineering is a powerful and prestigious profession. Engineers can save companies millions of pounds in the developed world by clever designs, and can save thousands of lives in the developing world by working on energy projects to provide power to their industries, or working on infrastructure projects such as water pipelines to give people clean water. Engineers can make a big 'difference' in the world. An engineer will use scientific laws to solve practical problems. It is difficult to differentiate between scientists and engineers, but one way is to view a scientist as asking ·why ?- and then he/she researches the answer to the question. By contrast, engineers want to know "now" to solve a problem, and how to implement that solution.
'You see things and you say "Why?" But / dream things that never were; and I say "Why not?" George Bernard Shaw.
© Penspen 2007
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Country
Reserv es (billions of barrels)
USA
22 12 78 10 60 180 30 24 113 89 97 98 261 18 15
Mexico Venezuela Norway Russia Canada Libya Nigeria Iraq Iran Kuwait UAE Saudi Arabia China Qatar
Table 2. Countrie s w it h th e Majo r Oil Reserve s
1.3 Legal Duties We all must obey national and international laws . Engineers will be fac ed with many laws (for example, contract law), and hence we need to consider our legal duties. This paper is not an in-depth analysis of our legal duties; these will vary from country to country . However, we will cover certain legal responsibilities: this is important as engineers can be held responsible for their actions and face penalties. Remember... we live in a very litigious society; be aware of all your duties and responsibilities, and always put safety first.
1.4 Responsibilities ~Responsibility: A detachable burden easily shifted to the shoulders of God, Fate, Fortune, Luck or one's neighbour. In the days of astrology it was customary to unload it upon a star. " Ambrose Bierce. The Devil's Dictionary, 1911.
We have many responsibilities in our lives. They can be family (e.g. care for your children), social (e.g. care for your neighbour), professional (e.g. care for your clients), spiritual (e.g. satisfying our conscience) and political (e .g . care for developing countries). First of all... what is 'responsibility'? Responsibility usually means we are expected to achieve or maintain a resu lt, as we have the required knowledge. It does not require 'perfection'. because we may not always achieve the result: •
a responsibl e physician may see a patient die;
•
a responsible engineer may witness his design failing in an unfore seen accident.
© Penspen 2007
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Engineers have many responsibilities. We always think of three of the more obvious: •
professional - the responsibility that arises from a special knowledge ;
•
company- these are our 'official' or specified duties in our job;
•
legal- those required by society.
We would expect to behave in a professional manner at all times, as we are called professional engineers. Also, we would always expect to behave in a right and proper manner to our company, within the law of the land, to satisfy both our own morals, and the employment contract. Therefore, we are familiar with our professional and work obligations, but engineers now have many responsibilities beyond these simplistic professional ones. When we design a component, conduct a calculation, give a view, etc.• we are making a decision, and hence we have responsibilities to all 'stakeholders' in those decisions. These stakeholders include the engineer and others; for example: •
the company we work for;
•
the client we are making the decision for;
•
any person or environment that may be affected by this decision.
We can illustrate this by considering designing a hotel elevator: the stakeholders are our client who ordered the elevator, the owner of the hotel, and aU persons who travel in the elevator. Consequently, we are answerable to many stakeholders and liable for our decisio ns, and our 'professionalism' goes beyond ourselves and our company. Additionally, we are now in a 'global' economy, and engineers will increasingly be asked to work on projects in countries that have poor human rights, or poor environmental records. This means we may be faced with questions of morality and conscience, Again. an engineer must now consider these aspects in his or her work. All the above can be grouped into three areas: •
loyalty: to your profession and company;
•
ethics: in dealing with matters of conscience and morality;
•
duty of care: to all stakeholders in your decision-making.
Obviously, all the above are linked together, but to give this paper some structure we will start by talking about 'loyalty' and 'ethics', then move on to 'duly of care',
© Penspen 2007
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2.
LOYALTY [1,2]
2.1 Wh at is ' Loyalt y'? You can find various dictionary definitions of loyalty. He re is one:
'Loyafty - friendship or duty towards something or somebody'. Loyalty is a confusing concept. We can see people being 'loyal' to fam ily members, even a football te am. but to a company? To a profe ssion ? To a custo mer?
A good example of loyalty is a pet. Dogs and cats can fetch a stick, or purr on your knee, and only requ ire a me al per da y in return . A dog is fanatica lly loyal : a dog will exh ibi t life long loyal ty to eve rythin g, rang ing from yo u, to an old slip per . Even if yo u do not feed a dog , it will rema in by yo ur side. A cat is different: his or her loyalty is mer ely a business deal: feed me, and yo u have my loyalt y and affections, sto p feed ing me, and
I'm gone . Also, a dog's loyalty is unquestionable: shout 'sit' into a room full of cats and dogs, and all the dogs will sit, but the cats will look long and hard at you, and think - "are you winding me up?". A cat can show real and ferocious loyalty: try and steal a kitten from its mother; but it cannot understand why dogs' loyalty can extend to giving up their lives in the protection of a deflated football.
We will now look at loyalty issues that an engineer will face in his or her profession. 2.2 loyalty to a Company - an Older View Our forefathers viewed loyalty to a company as a mark of distinction. Loyalty was usually identified by long service . Today, this can be the 'kiss of death' to your career. Prospective employe rs may be suspicious of an applicant who has been with one company for a long time. Where is the ambition? Where is the varied experience? Where are the new skills? Obviously, any new employer will be suspicious of an applicant who cha nges their job every six months, so there is a balance needed when considering how long to stay with a company in terms of your career prospects.
2,3 Loyalty - the Modern View Loyalty is a quality that is becoming increasingly difficult to find, whether it is employee loyalty to a company, or consumer loyalty to a product. In the past, employees believed when they were hired by a company, it would last until they retired. Start ing in the 1980s, as companies sought to increase profits, workers' perceptions of lifetime employment were shattered by corporate downsizing, company relocations to ot her states or countries, and static wages. This is why older workers are more likely to express corporate loyalty , but they are also more likely to feel betrayed by corpora te actions. A report on corpora te hiring priorities gives us an insight into how the 'new ' world views loyalty: the survey was conducted by Vault Reports. a New York City-based employment research firm. Vault Reports asked college career-centre professionals what they thought employers are looking for in new hires. The top items were phrases such as "team player," "intelligence" and "professional demeanour." Finishing next to last, No. 10 on a list of 11 items, was "loyalty.
© Penspen 2007
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The above shows us that there is a modern (lower importance) view of loyalty. However , in this section we are looking more at loyalty to a company in terms of decisions made 'on the job' rather than to further your career.
2.4 Corporate loyalty Most professional engineers are employed by an organisation. An engineer will have an employment contract and 'Terms and Conditions' will require some 'loyalty', e.g. a long notice period, and a company's rewards package (e.g. large pension) may be seen as warranting some loyalty in return. Ensuring loyalty by good pensions, company cars, etc. , is a simple buying method. Beware of companies and managers who use words such as 'pride. commitment, teamwork ' as a reason to work harder or longer: these are words that managers use to get staff to work for free. Instead, companies need to offer tangible benefits as incentives for loyal staff. Hence, policies and procedures must be in place that give staff confidence that any loyalty they show will be rewarded . For example, longer notice periods, company equity schemes, and other rewards for competence and commitment. This is similar to supermarkets' 'loyalty' cards - because they pay you back (1% refund of everything you spend) for your custom. Again, a simple financial deal.
2.5 loyalty: A l egal Definition 'l oyalty' is a very abstract word, but a definition [3] from a court in Maryland, USA gives some important guidance: '... an implied duty that an employee is to act solely for the benefit of his or her employers in all matters within the scope of employment. '
2.6 loyalty and the Engineer An engineer must make his or her own decisions on loyalty to a company in terms of his or her career progression; however, in our professional work, we do not owe unqualified loyalty to a company, as this would be a sacrifice of an employee's autonomy. For example, a maintenance manager who tells a maintenance engineer to 'watch costs', is behaving in a reasonable, legitimate manner, but if this manager asks the engineer to cut costs by neglecting certain agreed procedures, then the engineer is placed in a difficult position. The above legal definition of loyalty helps an engineer in these circumstances; if an illegal or dangerous act is being proposed, it is not to the benefit of the company. And remember, in certain circumstances, a professional code of ethics may contain an expression of public policy, and a professional may be expected to abide by this professional code as well as federal and state laws. That duty may oblige them to decline certain acts requested by an employer. Note that almost all the engineering codes of ethics in the USA. include as a provision, "Engineers shaff act in professional matters for each employer or client as faithful agents ." We will discuss this further under 'ethics', as we must never let our company or personal loyalties break ethical barriers. The major point for an engineer to remember is that their main loyalty and responsibility is to the general public, whom they serve. And this leads to a simple priority for any engineer: safety! © Penspen 2007
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© Pens pen 2007
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3.
ENGINEERS' ETHICS
'What is moral ;s what you feel good after, and what is immoral is what you feel bad afte r'. Ernest Hemingway. Engineering is an important and learned profession. As members of this profession , eng ineers are expected to exhib it the highest standards of honesty and integrity. Additionally, engineers must perform under a standard of professional behaviour tha t require s adherence to the highest principles of ethical conduct. "Ethics" has at least three mean ings in English: it ca n be [4]:
1. a synonym for ordi nary morality, • "Morality", refers to those standards of conduct everyone (every rational person at his rational best) wants every other to follow even if everyone else's following them would mean having to follow them too. Morality (in this sense) is the same for everyone, engineers included. 2. the name for a field of philosophy, or 3. the name for a set of special (mora lly permissible) standards (for example , engineering ethics , see Section 3.2.1)). This section cons iders ethics and engineering, but other aspects of life cut across eng ineering . For example. the British Government recentl y (December 2001 ) was faced with an eth ical problem when asked to grant an export licen ce. Tanzania , one of the world's poorest countries (half the popu lation do not have access to clean water. over half live below the poverty line, with a per cap ita income of $250 a year ) and in the top 10 list of most corrupt countries in the world. placed a S40m i11ion order with a British Company for a military air traffic control system. Internationa l 'arms' dealing has been recognised as corrupt for decades. Th e ord er, if accepted , protected 250 eng ineering jobs in the UK. How should the government react. and how can the 250 engineers ethically justify producing the equipment?
3.1 Moral St andards In 'Prospects for International Standa rds' by Vivian W eil she reflects on common moral standards; we refer to them as our 'common mora lity' . Her colleag ue, Michael Davis has usefull y cha racterized our common morali ty : "Don't kill," "Don't deceive," and "Don 't cheat" are among the stand ards of our common morality . Our common morality, provides a fundamental framework of standards to appeal to in reaso ning about cases. We have an addi tional framework: the codes of ethics promoted by the professions through their professional asso ciations. These ethica l stand ards are special sets of standards adopted by occupational groups and binding upon the members of the group, because they are members of the group.
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3.2 Professional Standards/Ethics)
Using the above description of common moral ity, allows professional standards to be defined as those "morally permissible standards of conduct each member of som e particular occupational group wants every other member of the group to follow, even if everyone else 's following them would mean having to follow them too. H
A profession's ethical standards must be compatible with OU f common morality, but they go beyond : they interpret our common morality for the specifi c details of work of a part icular occupational group. For example, almost all the engineering codes of ethics in the U.S. include as a provision. "Engineers shall act in pro fession al matters for each employer or client as faithful agents. Avoiding injury to the employer or client is a requirement for enginee rs, specific to their conditions of practice . 8
3.2.1 Engineers' Responsibilities and Ethics The Amer ican Society of Mechan ical Engineers (ASME) considers that eng ineers should uphold and advance the integrity. honour, and dignity of the engineering profe ssion by: • Using their knowledge and skill for the enhancemen t of human welfare; •
Being honest and impartia l. and serving with fidelity the public. their employers and clients;
•
Strivin g to increase the competence and prestige of the engineering profession .
These fundamen tal responsibilities lead onto a set of fund amental rules ('canons'): 1. Engineers shall hold paramount the safety, health and welfare of the public... 2. Engineers shall perform services only in areas of their com petence. 3. Engineers shall continue their professional development throughout their careers and ... provide oppo rtunit ies for the .. . deve lopment of those eng ineers under their supervision. 4 . Engineers shall act in profes siona l matters for each emp loyer or client. .. and shall avoid conflicts of interest. 5. Engineers shall build their profe ssional reputation on the merit of their services and shall not compete unfa irly with others . 6. Engineers shall associate only with reputable person s or organisation s. 7. Engineers shall issue public statements only in an objective and truth ful man ner. 8. Engineers shall consider environmental impact in... their professional dut ies.Othe r professiona l eng ineering organ isations have similar rules; for example, the Engineering Council in the UK under its 'Roles and Responsibilities of Chartered Engineers' (17 ) states that an eng ineer has '... a responsibility to society with regard to safety, to their legal and contractual obligations, and for the ethicaf and environmental impact of their work'. 3.2.2 'Canon t ' Professional codes, then, reflect our comm on moral ity and the circumstances of practice in a part icular society. Circumstances change and codes undergo revision , as profession al societies respond to press ures from outside and from within the world of practice. Currently, profe ssional engine ering societies in the USA are beginning to respon d to widespread concern about the environment. Some engine ering societ ies have consid ered whether existing codes already encompa ss protection of the environment, by way of Canon 1 (see Section 3.2.1): "Engineers shall hold paramount the safety, health, and welfare of the pu blic in the performance of their
3
'Ethics' is the conventionalterm in the USA for 'professional standa rds'.
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professional duties." Two societies have added provisions regarding the environment to their codes.
Around 1970, all the major professions came under closer scrutiny than before, and they had to respond to demands for accountab ility to the public. Canon 1 of the engineers' codes serves as a touchstone for engineers and engineering students who are trying to resolve problems . It does not imply specific solutions, but it reminds engineers of their weightiest obligation as professionals. Ethical codes, like technical codes, respond to problems that engineers commonly encounter. At each stage in their development, codes represent the consensus of a particular community of engineering professionals, and they, in turn, help to define a community of engineeri ng professionals. Both ethical and technical standards are part of and expressions of the expertise of engineers. 3.2.3 Do we have to take note of Engineering Institution's Ethics Policies? If we are a member of an engineering institution that has an ethics policy, society will expect us to adhere to it. Many engineers are not members of engineering societies: membership, and obeying their rules, are not legal requirements, Do societies ethics codes, etc., apply to these engineers? An engineer 's obligations do not rest on an 'oath' or membership of a society; however, if you call yourself an 'engineer' or have an 'engineer' job title , society (and the law) will expect you to behave as a responsible engineer. The law would consider engineering societies rules, and if they are rational, they will expect any engineer to follow them . You may not be a member of ASME, etc., but a lawyer and society may consider you have a 'contract implied by law' with this type of society.3.2.4 Engineering Standards and Codes" Safety is a leading ethical concern in engineering: this concern underlies technical standards and becomes explicit in codes of ethics. Engineering knowledge and guidance is translated into codes and standards that are used by industries, but all codes and standards leave scope for individual j udgment, and this is where ethical codes help engineers. Standards give engineers guidance and advice in a straightforward manner; however, the process by which codes shape practice is not straightforward. As a British scholar recently said, "Why should the use of standards be more straightforward than their development? ", Engineering societies voluntarily produce not only standards but also documented discussions and accounts of debates that occur in the process of deliberating about standards. These are published in their journals , websites, etc.. 3.2.5 Linking Engineering Standards and Laws It is not usually legally mandatory to conform to engineering standards, but following them satisfies legal safety regulations, which are mandatory.
What is the difference between a 'code' and a 'standard'? ASME considers a 'standard' as ... 'a set of technical definit ions and guidelines - "how to" instructions for designers and manufacturers. Standards, which can run from a few paragraphs to hundreds of pages, are written by experts '. Standar ds are considered voluntary because they serve as guidelines , not having the force of law. A 'code' is... 'a standa rd that has been adopted by one or more governmental bodies and has the force of law, or when it has been incorporated into a business contract' ,
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The failure to meet appropriate engineering standards, even when there is no violat ion of government regulations, can leave a company vulnerable in a product liability laws uit. There is, then , in the face of legal standards, a basis for continuing to emphasize good engineering standards, ethical as well as techn ical, and to advance those standards by incorporating new knowledge.
Don't Forget Trainin g!
There is nothing training cannot do. Nothing is above its reach. It can turn bad morals to good; it can destroy bad principles and recreate good ones; it can lift men to angelship'. Mark Twain . All engineers are required to continue their professional development (See Section 3.2.1). We must keep up to date, and be aware of new technologies and methods. If we do not - we are failing in our duties . In some countries it is a legal requirement to have a formal training programme for pipeline engineers. For example, in the USA, the Federal Register Part 49 CFR 192.763 (pipeline integrity management in high consequence areas) requires: 'An operator's integrity management program must provide that each supervisor. .. has appropriate training or experience in the area for which the person is responsible {and] must provide criteria for the qualification of persons who review or analyze results from integrity assessments and evaluations .... ' We will mention training again in Section 5.4.2 .
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4. THE ENGINEER AND CLIMATE CHANGE [5-7] We cannot ta'k about the ethics of engineers in the oil and gas business without talki ng about its impact on the environment .
Oil and gas brings many benefits to society, and is an essential part of modernday living: we cannot survive withou t it. In recen t years, many scientists have highlighted the impact on our environmen t of burning fossil fuels: this impact can be highly damaging, part icularly on our climate. and have long term cons equences to our planet. Over the last two decades , scientists have observed a slight increase in temperature on the surface of the earths. Some attribute this to an increased concentration of 'greenhouse gases' in the atmosphere. The most important greenhouse gases are : carbon dioxide (C0 2 ) , methane, nitrous oxide , hydrofluorocarbons, perfluorocarbons , and sulphur hexafl uoride. The main greenhouse gas of conce rn to policy makers is carbon dioxide . It traps some of the radiation that would otherwise be lost to space, and causes the Earth's atmosphere to be warmer than it would otherwise be. We all contribute to greenhouse gases in the atmosphere : driving a car , using electri city obtained from fossil fue ls, etc. Similarl y, when farmers in Braz il, or the United Stat es or China, clear or burn forests to create new farm or grazing lands, emissions are also increased. That explains why actions by man are central to the climate change debate.
4.1 Is Climate Change Really a Problem [8]? Thousands of climate scientists, ecologists , technologists and economists from round the world formed an Inter-governmental Panel on Climate Change in 1988, under the auspices of the Un ited Nat ions. The panel's pioneering assessments amount to a scientific consensus on climate chang e, its likely impacts, and what we can do about it. Its early reports persuad ed governments of the seriousness of the problem and informed the negotiations of the Kyoto Prot ocol (see next section). One of the centra l conclusions of the panel's work to date is that, whateve r we do now , significant climate change is now unavoidable. It will take decades to bring emiss ions of greenhouse gases under sufficien t control that the concentrations of the gases in the air stop rising. The International Energy Auth ority's (lEA) W orld Energy Outlook 2002 stated that global ene rgyrelat ed emissions of carbon diox ide are projected to increase by 1.8% per year from 2000 to 2030, reaching 38 billion tonnes in 2030. Th is is 16 billion tonnes, or 70% more than tod ay (200 2). Two-th irds of the increase will come in developing countries. China alone will contribute a quarter of the increase in carbon dioxide em issions , or 3.6 billion tonnes, bring ing its total emissions to 6.7 billion tonn es per year in 2030 . Even then , however, Chinese emissions remain well below those of the United States .
4.2 Kyoto Protocol
5 CO2 levels have risen from an average of 280 ppm (parts per million) over the last millennium to a current level of 370 ppm and continue to rise by 1.5 ppm per annum. Indeed. levels are at their highest for 400.000 years. Most scientists believe that human activity is causing that increase. Concurrently. an average global temperature rise of 0.6 e C has been observed since 1860 [9].
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In 1979, the first United Nations' World Climate Conference explored how climate change might affect human activities, and issued a declaration calling on the world's governments "to foresee and prevent potential man-made changes in climate that might be adverse to the well-being of humanity". The United Nations subsequently helped to develop the 'Kyoto Protocol': this protocol requires participating nations - almost all from the developed world - to reduce their greenhouse gas emissions to five percent below 1990 levels during the five years from 2008 to 2012. 4.3 Is Saving th e Plan et a Prioriy? Is cutting the use of fossil fuels, and money spent on controlling global warming, a good thing? It is estimated that the implementation of the Kyoto agreement is $150 billion/year, and its effect would not be seen for centuries; but, for half that sum, we could provide clean water, health care and basic education to all of the world's population. If we were to ask the father of an uneducated, starving, ailing family in the developing world how we should spend $150 billion this year, he will not say 'save the planet', he will ask 'save my family'. 4.4 Climate Change and the Pipeline Engineer Pipeline engineers work in a business that is known to create global warming; consequently, they need to be confident that their profession and companies understand this impact and are contributing to its mitigation. For example, many oil and gas majors are working on 'greener' fuels, but this is a slow process: a review by the UK's Royal Academy of Engineering of the cost of generating electricity in the UK from different energy sources concluded that natural gas was the best option, and renewable energy sources were more expensive [10], Table 3. An engineer has to accept the damaging aspects of burning fossil fuels, and be convinced that on balance - it contributes to the welfare of the people it serves, and that also his/her company is aware of their duties in reducing these damaging aspects. Method of Generating Electricity
Cost (pence IkWho ur)
Gas-fired combined cycle gas turbine (CCGT) Nuclear fission plant
2.2 2.3 2.5 2.6 3.2 3.7-5.4' 5.5-7.2' 6.6
Coal -fired pulverised-fuel (PF) steam plant Coal-fired circulating fluidized bed (CFB) steam plant Coal-fired integrated gasification combined cycle (IGCC) Onshore wind farm Offshore wind farm Wave and marine technologies ,
Cost Increases If back-up power generation IS needed . The costs Ignore environment Impact.
Table 3 Alternative Energy for Electricity Generat ion
6 These costs assume no penally is being paid by the fossil fuels for crealing CO 2 , If taxes /penalties are levied, then nuclea r and the renewabl e sources become more competitive. 7 1 pence £0.01. 8 Coal is one of til e 'dirtiest' fuels and produces the mos t CO 2 : hence, it is causing most dama ge in terms of global warming .
=
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5.
STANDARD (DUTY) OF CARE
Before we start this section, we need to note the single word that sums up an engineer's responsibilities, ethics, stand ard of care, etc.: SA FETY! Engineers have always been responsible for their work, and their failures; for example , 3000 years ago. Hammurabi the greatest ruler (1795bc-1750bc) of Babyion", produced a remarkable list of codes and laws for his people. It is the earliest complete legal code known. They were engraved in 2.4m high blocks of granite . One of these laws was ... 'If a builder builds a house for some one, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shaff be put to death '.
5.1 Engineer's Duty Engineers have a duty to provide their services in a manner consistent with the "standard of care" of their professions. Two good working definition of the standard of care (both taken from the USA legal system) of a professional are: •
that level or quality of service ordinarily provided by other normally competent practitioners of good standing in that field . contemporaneously providing similar services in the same locality and under the same circumstances '; or
that which is commonly posse ssed by members of that profession or trade on good standing. It is not that of the most highly skilled, nor is it that of the average member of the profession or trade. since those who have less than median or average skiff may still be competent and qualified ' [1 1].An engineer's service need not be perfect: since the engineer, when providing professional services, is using judgment gained from experience and learning , and is usually providing those services in situations where a certain amount of unknown or uncontrollable factors are common, some level of error in those services is allowed. •
When you hire an engineer you "purchase service, not insurance." so you are not justified in expecting perfection or infallibility, only "reasonable care and competence". The fact that an engineer makes a mistake that causes injury or damage, is not sufficient to lead to professional liability on the part of the engineer. In order for there to be professional liability, it must be proven the services were professionally negligent, that is, they fell beneath the standard of care of the profession. When one hires an engineer, one accepts the risk, and the liability, of that professional making a mistake similar to mistakes other normally competent engineers make, using reasonable diligence and their best judgment. The standard of care is not what an engineer should have done in a particular instance, it is not what others sayan engineer would do, or what others say they themselves would have done , it is j ust what competent engineers actually did in similar circumstances.
5.2 'Error' Error is fact of life: "To err is human. "
9
Babylon is Iraq and the northern parts of Syria.
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Some error comes from variability and uncertainty in what the engineer is dealing with: real materials, natural and man-made loads, and humans and their organizations. Error can lead to failure , which can cause injury, and result in damages. An engineer is not liable, or responsib le, for damages from every error . Society has decided, through case law, that when you hire an engineer, you buy the engineer's normal errors . However, if the error is shown to have been worse than a certain level of error, the engineer is liable. That level, the line between non-negligent and negligent error, is the "standard of care." We will now deal with both negligence and standard of care .
5.3 Determining 'Standard of Care' 5.3.1 GeneralA trier of fact (a judge or jury), has to determine what the 'standard of care ' is and whether an engineer has failed to achieve that level of performance. They do so by hearing expert testimony. People who are qualified as experts express opinions as to the standard of care and as to the defendant engineer's performance relative to that standard. The trier of fact weighs the testimony from all sides and decides in each case what the standard of care was and whether the defendant met it. Jury instructions have been standardised. A Bench Approved Jury Instruction in the USA reads : "In performing professional services for a client, a (structural engineer) has the duty to have that degree of learning and skill ordinarily possessed by reputable (structural engineers), practicing in the same or similar locality and under simifar circumstances. "It is (the structural engineer's) further duty to use the care and skiff ordinarily used in like cases by reputable members of the (structural engineering) profession practicing in the same or similar locality under similar circumstances, and to use reasonable diligence and (the structural engineer's) best judgment in the exercise of professional skiff and in the application of learning, in an effort to accomplish the purpose for which (the structural engineer) was employed.
"A failure to fulfil any such duty is negligence". Four key items in this instruction are worth repeating: •
...have learning and skill ordinarily possessed by reputable engineers practicing in the same or similar locality and under similar circumstances.
•
...use care and skill ordinarily possessed by reputable engineers practicing in the same or similar locality and under similar circumstances.
•
use reasonable diligence and best judgment.
•
to accomplish the purpose for which the engineer was employed .
If anyone of these conditions is not met, the engineer has failed to meet the standard of care, and is professionally negligent. Finally, it is worth repeating that the standard of care varies with time, locale and circumstances. 5.4. 'Neg ligence' and 'Competence' 5.4.1 'Negligence' You may be accused of 'negligence' in any profession. Section 5.2 noted that the line between a non-negligent and negligent error, is the "standard of care", and negligence is a failure in your standard of care. Obviously, you will not face litigation solely for not meeting this standard of care; in law, you can be called 'negligent' if [14] : © Penspen 2007
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•
a duty of care existed between parties ;
•
the defendant breached the duty;
•
as a result of that breach the claimant sustained damage.
To avoid being negligent an engineer must show that he/she has made all the 'preparations' that a reasonable man/woman (see next section) in this position would recognise to prevent unreasonable risk. In all civil cases the claimant is required to prove his or her case on the 'balance of probabilities'. This simply means a Judge has to be persuaded that the claimant's version of events is more likely to be true than the defendants. 5.4.2 'Competence' We often hear that an engineer needs to be 'competent'. A definition from a pipeline organisation [1 3] is: 'A Competent Person should have practical and theoretical knowl edge as well as sufficient experien ce of the particular machinery, plant or procedure involved to enable them to identify defects or weaknesses, and to assess their importance in relation to strengths and functions of the machinery'.
All engineers need to have the required basic qualifications, then ensure they are up-to-date with both 'practical and theoretical' knowledge. This means continual professional development; for example, the Institution of Mechanical Engineers in the UK requires its Chartered Engineers to be •... competent throughout their working life. by virtue of their education, training and experience ...', How does this relate to a pipeline engineer? Until recently, there have been no academic engineering courses specially for pipeline engineers. This is now changing: there is a dedicated pipeline engineering masters program at University of Newcastle, UK, and the Catholic University in Rio, and University of Calgary, are offering, or will offer, extensive pipeline engineering education at both under-graduate and post-graduate levels. Additionally , the American Society of Engineers now has a division devoted to pipeline systems. A basic education needs to be followed by both experience and continuous trainmq.. Note that training alone is not sufficient: 'Just because you 're trained for something, doesn't mean you're prepared for it '. Anonymous. It is of interest to list the modules on the University of Newcastle's masters proqram in pipeline engineering, to show how wide a pipeline engineer's knowledge needs to be. The modules are: •
Fundamentals of Pipeline Engineering;
•
Design and Construction;
•
Asset Management;
•
Economics for Pipeline Engineers;
•
Hydrocarbon Processing and Production;
•
Corrosion and Corrosion Control;
•
Materials and Fabrication
•
Dynamics of Offshore Installations;
•
Pipeline Structural Integrity;
•
Civil and Geo-technical Engineering;
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•
Safety and Environmental Engineering.
Obviously, it is a pipeline engineer's responsibility to ensure that any design or integrity assessment is correct. He/she should use the best possible practices available , check calculations, inputs and assumptions, and use all available data. These will include historical, current and circumstantial data (inspection data, operations records, maps, etc.). An appreciation of the wider practical issues, and an understanding of all engineering aspects of the problem are required. This will require excellent data management support and internal communications. 'Reasonab le Person' and 'Reasonable Care ' Section 5.3 discussed 'standard of care '. The legal profession also uses the phrases: 'reasonable care' and 'reasonable person'. 5.5.1 'Reasonable Care' and 'Accidents' Accidents happen ... but many 'accidents' should not be described as 'accidents'. If an 'accident' has preventable causes, it may become a criminal case! And the fact that the engineers involved in the 'accident' did not intend an accident to occur, is not a defence. Was it an 'accident waiting to happen? It is a question of 'reasonable care' : did the engineer(s) exercise 'reasonable care '? In the USA 'reasonable care' [12] is .. . 'the amount of care that a reasonably prudent person would use in similar circumstances' and we can easily relate this requirement back to our standard of care. If an engineer does not exercise this 'reasonable care ' he/she may face prosecution. 5.5.2 The 'Reasonable ' Person The standard of conduct that the law imposes can perhaps best be understood in terms of the hypothetical "reasonable person" [14]. The law presumes that there is a standard of behaviour that a person of 'ordinary prudence , skill and care' would follow in all situations, so as to avoid creating unreasonable risks of harm to others. When dealing with professionals, or persons of superior learning or skill (such as engineers) , the law imposes an even higher standard of care and diligence. In effect, it hypothesises a "reasonable engineer," whose conduct is guided by his or her special knowledge and expertise. In all instances, however, it is a jury of lay people who must decide whether challenged behaviour was, or was not, reasonable.
The Engineer and the Law The previous sections have covered both 'standard of care' and 'reasonab le person'. These are society's expectations and requirements for engineers , and these are the legal tests.
5.6.1 The Guilty Verdict... Legal systems , laws and responsibilities vary around the world , but Section 5.4.1 summarised how an engineer may face litigation if he/she has been negligent. Senior staff or directors of engineering companies may be liable to prosecution if they can be shown to have committed an offence: •
with their consent or connivance; or
•
it was attributable to any neglect on the part of the officer/manager.
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The test will be subjective: has the officer/manager deliberately turned a blind eye to something, or deliberately ran a safety risk? To prove guilt, the defendant must be proven: •
personally guilty of manslaughter; and
•
be identified as the company's directing mind and will, on the subject: this 'identification principle' is the problem area.5.6.2 Pipelines in the USA
Any major incident involving critical private infrastructure will be the subject of close law enforcement scrutiny. In the USA, for pipelines, these law enforcement agencies are: FBI, US Environmental Protection Agency, Department of Transportation, US Coast Guard. These agencies will consider any incident causing environmental damage or injuries as criminal cases. An incident would be considered a crime if this 'harm' was linked to 'culpable conduct' [12}. The following evidence would show 'culpable conduct': •
history of repeat violations;
•
deliberate behaviour;
•
efforts to conceal;
•
tampering with monitoring devices;
•
activities such as false statements, obstruction, etc.
Companies 10 would face charges after the prosecutors have considered: •
was the offence serious (e.g. great harm)?
•
were wrong-doings common in the company and corporate?
•
was management aware of this?
•
is there is a history of offences?
•
did the company quickly identify and report the incident and respond to it effectively?
•
has the company a 'compliance program' in place, and is it being applied diligently (e.g. were wronq-doers quickly disciplined)?
• would innocent shareholders or employees suffer disproport ionately?5.6.3 This is a Real Issue! Pipeline engineers need to be very careful [15]... in 2003, a new level of personal liability was reached in the USA when a federal judge sentenced two pipeline engineers to jail time, following an explosion of a gasoline pipeline in Bellingham, Was hington in 1999. It was the first time ever that pipeline employees had received jail time in connection with a pipeline accident. A former company official was sentenced to six months in jail, while a control room manager received 30 days in prison and 30 days of home detention. A third employee , whose job involved monitoring the section of pipeline that ruptured, received a one-year probation and 150 hours of community service. It was alleged that the accident resulted from inadequate pipeline inspections following excavation work done five years earlier.
10 In the USA a corporation can be charged with wrong doings - and the executives can be liable. This is because corporations act through the actions of individua ls. Therefore, individuals can be liable to prosecution.
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6.
DISCUSSION
6.1 Globalisation
We are experiencing 'globa lisation' that allows the economic integration of all world trading reg ions (21), and the oil and gas business is a key part of this change: we can work in Houston today and Chad tomorrow . This means that the pipeline business and pipeline engineers have to adapt to this change and come to terms with the ethical issues it raises . In a world where oil and gas is, and will be, extracted from poor and sometimes corrup t countries, and where oil and gas majors cont inue to make record profits , engineers have to work to th e highest ethical standards . Engineers hav e to take a balanced view of their business and their own values, but certa inly eng ineers should not be aga inst mult i-national companies making a profi t, the expansion of their business, or to globalisation: as Kof Annan, the UN secretary-general said , 'The poo r are not poor because of too much gfobafisation , but because of toot little. '. Kofi Annan speaks with authority , but we must be carefu l with our globalisation : the new weal th it can create can have both immed iate and long term negat ive effects: for example , if we create highly paid jobs in the oil and gas business we may reduce the attractiveness of becoming doctors or teachers in that coun try . Similarly, a short term focus on oil and gas riches may lead to long term harm in other industries. 6.2 Growth in the Developi ng World Pipelines will be a key growth area as we expand our energy infrastructures around the world ; consequently , pipeline engineers have key roles in our energy future. The world already consumes over 28,000,000,000 barrels (1 barre l = 159litres) of oil per year . A 11 barrel of oil is currently (2005) about $US50: so, the oil business is worth $1.4 x 10 per year! And we are expanding the oil and gas business: we are plann ing pipelines in new regions , and pipelines will be needed in many countries in the future , as these countries either have unused energy reserves , or energy needs . These are the regions pipeline eng ineering companies and engineers will be working in the future. Surpris ingly, it is the deve loping world that is going to acco unt for the growth in energy demand . Cons ider the huge increase in the price of a barrel of oil in 2004 : this major increase was not due to demand in the develop ed world: it was due to demand in the developing world [16]:
Regi on
Increase in dem and for oil, 1973
USA
+16%
European Union (EU)
~6%
Developing Countries
+203%
2003
Table 4. Increase in Demand for Oil in the Developed and Devel oping World . The deve loping countries are now (200 3) consu ming over 25 million barrels of oil per day , compared to about 20 million barrels per day in the USA, and about 14 million barrels in the EU.
r
This increase will continue; for example, Afghanistan is a very poor country , but it has 120 billion cubic metres of gas reserves, and 125 million tons of coal reserves . However, curren tly, 85% of
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wood,
the energy needs of Afghanistan are met by 'biomass!" energy , i.e, fuel animal dung and agriculture waste. Fuel wood accounts for about 75% of the energy needs (cooking and heating) in rural areas, where most of the Afghanistan population lives . Soon, pipeline enginee rs will be working in Afghanistan, developing these reserves , but will the Afghan people benefit, or the oil and gas majors? Do the Afghan people have a say in these developments? Will protection of historical cultures, safety, and the environment, be the prime development conside ration s? We need to show corporat e responsibility in these developing countries. Indeed ou r oil and gas majors are now addres sing such issues ; for examp le, BP has agreed with the government of Azerbaijan that both sides will ensure greater transparency over tax and royalty payments from BP's huge Baku-Tbilisi-Ceyhan pipeline. BP is also investing in agricul tural programmes to help local communities, and helping local companies to bid for contracts on the pipeline (22). National Grid Transco, a major distributor of electricity and gas in the UK, is using Aborigine workers on its project that is laying undersea cable from Melbourne to Tasmania (22). Engineers can be encouraged by such shows of corporate social responsibility.
6.3 Balanced View All engineers have responsibilities, but their prime responsibility is to 'safety'. They are bound by the legal system in their country of residence or operation , but also have to satisfy the following criteria in all aspects of their work: •
professional (institutional requirements);
•
legal ('standard of care'); and
•
ethical (moral).
So ... what can an engineer do to ensure he or she is behaving in an ethical manner, and for an ethical company? The first thing to do is to understand your company's values . Are you working for a company that gives good , fair value? Or do they try and squeeze the biggest profit, and look for gullible customers? 0 0 they have an ethics policy, and work to it? Does the company appreciate the wide responsibilities it has to all its stakeholders? Do you admire your bosses and colleagues for huma n values such as honesty, mentoring , intellect, hard work, wisdom, friendliness, fairness, etc ., or is the only admiration in their position and salary? Some compa nies are actively addressing staff concerns over ethical issues; fo r example, National Grid Transco, a major gas and electricity business in the UK, has cons ulted its 14,000 workforce and is working to a 'Framework for Responsible Business Practice' that provides details of its corpora te responsibili ties (22). The next thing an engineer needs to do is check his/her own values in the workplace: integrity, honesty, charity, etc.. Consequently, an engineer has to balance all ethical issues and decide on participation on a career, job or project. This may not be easy; an engineer working for a company that makes missiles could view the missiles as a weapon that ensures equity and peace in the world,
11 'Biomass' is organic materia l which has stored sunlight in the form of chemical energy. Biomass fuels include wood, wood waste , straw, manure, sugar cane , and many other by-products from a variety of agricultural processes .
© Penspen 2007
22
r:
whereas commu nities destroyed by the weapon can only see it as it is - a weapon of mass destruction. It is the same in the oil and gas business. The service sector in the pipeline busin ess is often faced with 'difficult' decisions in pricing jobs, and winning contracts in some countries and some companies. This problem has been aro und for many years and gives some elements of the service sector a really chequered history. And do not think the oil and gas majors are witho ut a chequered history. Anyone working for an oil and gas major who has never heard of the infamous 'Seven Sisters' shoul d quickly type that phrase into thei r search engi ne now....
6.4 Beware the Mon ey Trap ... We can be driven to unethical acts , or 'conflicts of interest' by greed: we want more money. On January 2, 2000, the New York Times reported , "Most partners {at] the world 's largest accounting firm violated rules prohibiting conflicts of interest by possessing investments in companies for which they performed 'independent audits'." An estimated 86.5 percent of the 2,698 partners had at least one such violation , for a total of 8,064 cases. Does mone y bring happ iness? There is mounting , clear evidence that it does not (18, 19, 20)1 First consider wha t you 'want' and wha t you 'need'. There is a big difference: when we see a sports car , or an expensive hand bag, 'desire' takes over and the distinct ion is lost. W e want the brief pleasu rable moment of acquisition. In many wa ys, we now have an excess of everything , excep t happiness! Most research supports the conclusion that money and material things are only weakly asso ciated with leading a good life. As income rises, the sense of happiness (now usually called 'wellbeing') rises. But only to a point. .. once a 'middle class ' level is reached, money is not linked to happiness. Con clusion? Needs can be satisfied , but 'wants' never can! We NEED foo d, clothes, medical care, tran sport , etc.. Once you have attained these needs , you are satisfied. Unfortun ately, the more you WANT, the more likely you are to feel disgruntled. W e can identify with this: I 'want' Pame la Anderson , but I 'need ' my wife ! The more you acquire, the more likely you are to feel controlle d by your possessions; for exampl e, if you buy an expensive car , you need money to run it, and this spend ing may affect your 'needs'. Plus, you will be obsessed with any scratch on it! Actually, these conclusions are not new; the Greek philosopher Epicurus believed that to be happy a person requ ires: food, water, shelter , warmth , friendship, and freed om of thought. He advocated a simple life. He believed we all have the capacity for a happy life, but we 'poison' our lives with needless anxieties and fears . So ... money , it turns out, is not the answer: once we have eno ugh to pay fo r life's basics, such as food and a roof over our heads: more money adds little to our happiness. Therefore , do not sell your ethics!
6,5 Wh at Turns an Eth ical Person into an Unet hical Person?W e will end by asking a question ... 'how can good, honest, ethical, people become unethical and dishonest in their work? We are often surprised when we hear about individ uals , who in their normal day-to-day lives are good and honest, but they have been shown to be the opposite in thei r professional lives .
© Penspen 2007
23
There are many reasons why people act unethically at work: it could be based on greed (financial incentives), ambition, or envy. These people have a problem - they are inherently unethical. or easily corrupted and require help. Ethical people wake up in the morning , and they are ethical throughout their day, regardless of what they do during that day. These people have no problems with ethics: they are inherently ethical. However, even the saints amongst us can behave unethically. Why? One reason is that people may fall under the 'spell' of a large corporation, and believe that actions that benefit the corporation , are ethical. Consider this extract from an article in the Economist in May 2004: u •• • the corporation is a psychopath. Like all psychopaths, the firm is singularly seft-interested: its purpose is to create wealth for its shareholders ... like all psychopaths, the firm is itrespoositite, because it puts others at risk to satisfy its profit-maximising goal. harming employees and customers. and damaging the environment.
The corporation manipulates everything. It is grandiose, always insisting that it is the best, or number one. It has no empathy, refuses to accept responsibility for its actions and feels no remorse. It relates to others only superficially. via make-believe versions of itseft manufactured by public-relations consultants and marketing men. In short... the corporation is clinically insane .... "
© Penspen 2007
24
7.
CONCLUSION
In a world where oil and gas is, and will be, extracted from poor and someti mes corrupt countries, where the fuels pipelines transport lead to climate change, where the oil and gas majors continue to make record profits, and where litigation is increasing, pipeline engineers must practice to the highest ethical standards.
Our responsibilities and ethics will require constant attention: this paper has provided a simple guide.
ACKNOWLEDGEMENTS The author would like to thank Pens pen Ltd. , UK , for permission to publish this pap er. The paper is based on the author's lectures on Engineering Ethics at the University of Newcastle, UK. It is
the final paper in a series of four papers (see also 1, 2, 21) that have covered management, change and ethical issues in engineering. For more details , or if you require a course on ethics in engineering, contact the author ([email protected]).
REFERENCES 1.
P. Hopkins 'The Challenge of Change in Engineering', Journal of Pipeline Integrity, Vol.
1, No 2, 2002. 2.
P. Hopkins, 'Surviving Change in the Pipeline Business', WTIA International Pipeline Integrity and Repairs Conference . Sydney, Australia. We lding Technology Institute of Australia. 9th March 2004.
3.
l. l. Lowery, 'Loyalty WoNW.lowery.tam u.edu.
4.
onlineethics.org.
5.
www.api.orq .
6.
WoNW.defra.gov.uk/environmentlclimatechange/O 1.htm
7.
http://www. metoffice.com/research/hadleycentre
8.
http://WoNw.environment-agency.gov.uk.
9.
http://www.t otal.com/csr2002/en/deve loppementidown load/fs04_GHG.pdf.
10.
Anon., 'The Cost of Generating Electricity'. Royal Academy of Engineering. UK . 2004.
11 .
Anon.. The Restatement (Second) of Torts, Pages 74-75, 1979.
12.
S P Solow , 'US Pipelines Face Increased Criminal Threat from Environmental Scrutiny', Oil and Gas J. Dec 22, 2003.
13.
Taken from Brazier v. Skipton Company (1962) His Lordship Winn, J. UK. www.ukopa.co.uk.
14.
Anon ., 'ASME Training Module C - Legal', Section C3, 'Torts'. American Society of Mechanical Engineers.
15.
a J Dykes , 'Entrepreneurial Contentiousness Marks Recent Trends In Pipeline Litigation ', Pipeline and Gas Journal. January, 2004 . p.22.
16.
D Wood. Materials World, January 2005. Pages 8-9.
© Penspen 2007
and
Professional
25
Rights',
Texas
A&M
University .
Heightened
17.
Anon ., 'Roles and Responsibilities of Chartered Engineers', Engineering Council, Document Ref: 2.1.1. Issue No: 2. SARTOR 3rd Edition Part 2 Document. 23 June 1998.
18.
G Easterbrook. 'What Money Can't BUY'. Sunday Times. December 28, 2003. p.5.3.
19.
G Easterbrook. 'The Progress Paradox: How Life Gets Better While People Feel Worse'. Published by Random House. USA.
20.
P Martin, 'Making Happy People', Published by the Fourth Estate. 2005.
21.
P Hopkins, 'Time to Change?', Pipes and Pipelines Journal, September-October 2000.
22.
Anon.,
© Penspen 2007
'Companies
that
Count',
26
Sunday
Times,
UK.
April
3rd
2005.
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Tutorials in Pipeline Defect Assessment
By Phil Hopkins & Andrew Cosham Penspen Group, UK
Rev 2003/1
Page 1 of Error! Boo km ar k not defined .
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TUTORIAL l ' LEAK/RUPTURE· WILL A PART WALL DEFECT FAIL AS A LEAK OR AS A RUPTURE?
1.
PROBLEM
A 305 mm (12") outs ide diameter pipeline with a nominal wall thickness of9.5 mm (0.374"), and grade X52 2, conveying natural gas, contains a defect of length 135 mm (5.31") . The local wall thickness, adjacent to the defec t, is 9.4 mm (0 .370"). The current operating pressure is 104 bar (150Spsi) , the design pressure is l S I bar (2625psi). The problem is to determine whether or not this defect will fail as a leak or a rupture.
2.
FITNESS FOR PURPOSE EQUATIONS
Predicting whether or not a part wall defect tails as a leak or a rupture is equivalent to calculating whether a through wall defect of an identicallength will fail. The standard equation for predicting the failure stress of a through wall defect is:
a j !(j =Ar
1
M~ I +O{~J if
~
1.l 5SM YS I
Pj
P,
failure pressure
(Jr
hoop stress at failure
M
bulging factor
a
flow strength
d
maximum depth of part wall defect
1 Note that some of these tutorials/worked examples use either actual or simplified pipe geometries. to ease the calculations. For example, linepipe is not usually supplied with an OD of 12" (it IS usually supplied as 12.75") . 2 Pipeline grades relate to the specified minimum yield strength (SMYS) of the linepipe steel. The grade X52 means an SMYS of 52000 lbf/in2• To convert from Ibflin 2 10 l\inun 2, multiply by 0.006895. Other conversions:
TOUGHNESS: lJ=0.738ftlb . PRESSURE CO;\VERs ro,,' U1\ITS: I bar = 14.5psi = 105 MPa = lU5 ::--J/m 2 = 0. I::--limm 2 STRESS CONVERSIO:-J U::--J ITS ' I hi = IUOU psi = 1000 Ibfiin2 = 6.R9 MPa = 6.R9 MN/m2 = fi.R9l\imm 2
Rev 2003/1
Page 1 of 15
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defect axial length pipe wall thickness
R
outside radius of pipe
SMYS specified minimum yield stress
If the hoop stress is greater than the predicted failure stress of the through wall defect. then the part wall defect is predicted to fail as a rupture (i.c. the length of the defect extends on failure). If the hoop stress is less than the predicted failure stress, then the part wall defect is predicted to tail as a leak.
Notes: I.
A variety of different definitions of the Folies factor exist. A li gure in the handout for the solution indicates how these different Folies factors effec t the results ofthe calculatio ns.
2. A variety of definitions of flow stress arc available. but in this case it is assumed that the flow stress is appro ximately 1.15 x S\1 YS.
Rev 2003/1
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TUTORIAL 2 WILL MY PART WALL DEFECT FAIL?
1.
PROBLEM
A 305mm ( 12") outside diameter pipeline with a nominal wall thickness of9.5 nun (0.374"), and grade X52, conveying natural gas, contains a ' flat bottomed' corrosion defect of dep th 3.X mm (0. 15") and length 135 mm (5.3 1"). The local wall thickness, adjacent to the defec t, is 9.4 mm (0.37"). The curren t maximum allowable operating pressure (MAOP) is !CM bar (1508psi). The pipeline is des igned to operate at 72 percent SMYS. The pre-commissioning hydrotesr pressure corresponded to a hoop stress equal to 100 percent SMYS (based on the nominal wall thickness). The problem is to determine whether or not the defect should be repaired. 2.
FITNESS FOR PURPOSE EQUATIONS
The standard equation for predicting the failure stress of a part wall is:
I - (~ ) 1-
d) _, (t,lf
cH=I +O{~J (j ~
l.l SSMYS
where: P,
failure pressure
af
hoop stress at failure
~1
bulging factor
a
flow strength
d
maximum depth of part wall defect
2e
defect axiallength pipe wall thickness
R
outside radius of pi pc
Rev 2003/1
Pa ge 3 of 15
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SMYS speci fied minimum yield stress
Note: I.
The ratio of defect dept h to wall thickness [d't) in the above eq uation ca n be replaced by the cross sectional area of the defect (A) di vided by the area of the pipe wall occupied by the defect. i.e. (A/(2e.t» . However. for a flat bottomed defe ct this reduces to (d.2c)/(t.2c), o r d /t.
2. A varicry of diffe rent definitions of the Folia.. factor cxist.. 3. A variety o f defin itions of flow stress arc avai lable, but in this ease it is assu med that the flow stress is approximately 1.15 x SMYS.
Rev 2003/1
Pag e 4 of 15
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WORKED EXAM PL E 3
ASSESSING THE RESULTS OF AN INTELLIGENT PIG RUN
1,
PROBLEM
A 305mm (1 2"') outside diameter pipeline with a nominal wall thickness of9 .5 mm (0.374"), and grade X52, conveying natural gas, has recently been inspected using an intelligent pig. The current maximum allowable operating pressure (t\IAO P) is 104 bar (1508psi). The pipeline is designed to operate at 72 percent SMYS. The precommissioning hydrotcst pressure correspo nded to a hoop stress equal to 100 percent SMYS (based on the nominal wall thickness). A number of corrosion defects have been detected in the pipeline, a summary of the corrosion defects, and any associated comments, is given below:
Depth, mm (in)
Lengt h, m m (in)
Local wall thickness, 111m (in)
Comments
3.H(0. 15" )
135 (5.3" )
9.4 (0.37")
Flat bottomed defect.
4 (0. 16")
304( 12")
8.6 (0.34")
Vel)' irregular shape.
3.2 (0,13'")
305 (12" )
9,2 (0.36")
May be associated with a scam weld.
5.2(0.2")
268 (10.6")
9 (0.35")
Two smaller sized defects are close by.
6 (0.24")
2 13 (8.4")
9.2 (0.36")
May be associated with a dent.
5 (0.2")
197 (7.8" )
9.2 (0.36")
None
3. 1 (0. 12" )
348 ( 13.7")
10. 1 (0.4")
This is in an offtake section of the line that is heavily pressure cycled.
2.5 (0. 1")
441 (1 7.4")
10.310.41" )
NOlle
4.3 (0.17")
292 ( 11.5")
10.3 (0.4 1")
In section of pipeline liable to earthquakes.
The operator has reduced the operating pressure to 47 bar (682psi), because of the inspection results. The problem:
1. Consider the comments. What do they mean. and how would they affect the assess ment? 2. Closer inspection of the defects show them all to be tlat-bottomed defects, not associated \vith welds. dents. other defects. or in pressure cycled lines or earthquake regions. Calculate the failure pressure of the corrosion defects, and comment on whether or not they should he repaired. 3. Which of the defects arc acceptable? What would be the implications of the operator seeking to raise the operat ing pressure to the design pressure?
Rev 200311
Page 5 of 15
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4. 1I0w should the defects be repaired, if thought to be significam" 5. Ilow would the length of time that the defects would take to fail be estimated? How would inspection intervals be set for these defects, if they were to be lcf in the pipeline? 6. \Vas the operato r right in reducing the pressure to 47 bar (6S2psi)?
A plot of the defect depth (expressed as a fraction of the nominal wall thickness) and the defect length is given below .
DEFECT DEPTH I WALL TIIICK."IE SS (nom)
1
0.9 0.8 0.7 T
0.6 T
0.5
T
T
0.4
T
T
T
0.3
T T
0.2 0.1
a
a
100
200
300
400
500
DEFE CT LENG T II. mm
Rev 2003/1
Page 6 of 15
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WORKED EXAMPLE 4 CORROSION
1.
PROBLEM
A corroded area of length 100 mm (3.94") and maximum depth 6.4 mm (0.25") has been found in a pipeline The pipeline geometry is 6 10 mm (24") outside diameter, 14.3 mm (0.562") wall thickness, grade X52. The design factor of the pipeline is 0.72. Calculate the failure stress using the original B31.G criterion, and the modified R3 1.G criterion . Determine whether or not the corrosion damage is acceptable.
2.
BASIC EQUATION
ANSIIASl\lE B31.G
1- - 231d a r =a I~ ~d _l_ 3 1 At -
1
l
Jb!ln1. I
)1U2- JatWge )f [;i!a(P,? lub1tl ~7 cl (tuM es
/M(Pp)CV 1(/
M~ 1+ 0 8( ~r (j ~
1.1 x SMYS .... ~
where:
~
· s i)..OJO
1VJe r 0
rTr
hoop stress at failure, Nmm"
a
flow stress
D
pipe diameter, mm
)1
QU.
ClfJ,.Ch.,
0i r U-
I {ctSD (ui!Yar
no D
.{,tdtV ,
ja tlC1
pipe wall thickness, mm d
defect depth, mm
I
axial length of defect, mm
l\lodificd B31.G
Rev 2003/1
Page 7 of 15
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d 1 0 _ _- .85 --;-1,-- ] _""1 1 _'o'J ',
1
.11 =
j
I )' -
1+ 0.627"\JDi
j
' 2 w,,"
I )' ,1.13 10for ( Ft5i I )' 550.0
0.00337,\ .; DI
for
( ~r > 50 0
if = SMYS + I Oksi where: OJ"
hoop stress at failure, Nmm?
a
flow stress
D
pipe d iameter. rnm pipe wall thickness. mm
d
defect depth. rnm
f
axiallength of defect. rnrn
.r>
Rev 2003/1
Page 8 of 15
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TUTORIAL 5 CORROSION
1.
PROBLEM
An area of corros ion o f length 190 mm (7.5") and max imum depth 5.0 mm (0 .2") has been found in a pipeline. The pipeline geometry is 762 mm (30") o utside diameter. 11 .9 mm (0 .469") wall thickness. grade X52 . Th e des ign fac tor o f the pipelin e is 0.72. The current max imum operati ng pressure is 70 bar ( 10 15psi). Determine whether or not the corrosion damage is acc eptable, and if it is not acceptable then deter mine the maximum safe ope rating pressure.
2.
BASIC EQUATION
~ todificd
IT/ =
1 a
AI =
M
H31.C
7]
' - 0.85 d I 1- OB5- -
1M
1
I )' J I )' 1+0.627'\ ,jOI - 0.00337\ ,jDI
= 0.032( ~r + 3.3
for
( .J~J2 $ 5 0.0
for
( ~r > 50.0
a =SAIl'S + IUksi where:
at
hoop stress at failure , Nmm" (IblYin2)
a
flow stress • . Nmm·2 (lbf/in2)
D
pipe diameter(2R). mm (in ) pipe wall thickness. mm (in)
d
defect depth . mm (in)
I
axial length of defect, 111m (in)
Rev 200311
Page 9 of 15
------
--
-
-
-
-
-
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WORKED EXAMPLE 6
ASSESSING A PLAIN DENT IN A PIPELINE
1.
PROBLEM
A 457mm ( IS") ou tside diameter pipel ine, 12.7 mm (0.5 in.) wall thickness, X52 has been den ted by a mechanical excavator. A detailed inspection of the sire of damage has revea led tha t the den t has a smooth profile and that there is no associated metal loss defects or crack ing. The de nt is not adjacent to a weld. The dent dep th is 3.5% of the pipeline diameter. measured at pressure. The pipeline is pressu re cycled from 52 bar to 86 bar (750 psi to 1250 psi) once a day. The pipeline is 10 years old and has a des ign life o f 50 yea rs. Is the den t acceptable under sta tic internal pressure loading and cycl ic internal pressure load ing? [Use the Fowler (SES) model for assessi ng the fatigue life o f a plain dent]
2.
BASIC EQUATION
Fatigue life of a plain dent:
where: N
fatigue life, cycles
[tt>>.a .p ]
'stress intensification factor' (sec Tab le 1)
tJ.p
cyclic pre ssu re, psi
Spring back correction:
D" 2R
= 1.43 2DrR -
0.0023
2R
nomi nal diamete r of the pipe
Do
dent depth meas ured at zero pressure
Dr
dent depth meas ured at pressure
Rev 200 3/1
Page 10 0115
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Table
J-
[6a]
Values of dP
D/l
A member of Penspen Group
,
foran average operating pressure of 1000 psi".
18
20
25
30
35
40
45
50
1
13.94
13.25
15 00
20.93
29.80
38.68
47.55
56.43
2
19.64
21.18
25.20
32.53
39.87
47.20
5453
61.8 7
3
25.35
29.11
38.34
44 .14
49 .93
55.72
61.51
67.31
4
31.05
37.04
51.49
55 .74
59 .99
64.24
68.50
72.75
5
36.76
4497
64.63
67 .34
70.05
72.77
75.48
78 .19
6
42.46
52 .89
77.78
78.95
80 .12
8129
82.46
83 .63
7
48.17
6082
90.92
8
53.87
68.75
104.1
9
59.58
76.68
117.2
10
65.28
84.61
130.4
11
70.99
92.53
143.5
DoI2R (%)
Taken from: FO\VLERJ .R.; Criteria for Dent Acceptability In Offshon' Pipelines, UTe 73 11, 25 th Offshore 1h Technolo gy Conference. Houston. Texas. 3td. 6 May 1993. pp 481-493. 3
Rev 2003 /1
Pa ge 1 1 0115
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r:
WORKED EXAMPLE 7 ASSESSING DENTS WITH DEFECTS
1.
PROBLEM
A 9l4mm (36") outside diame ter pipeline, 9.9 nun (0.4 in.) wa ll thickness, and grade X52 has been dented and gouged during constructi on. The dent is 70 mm (2.75") deep ., and the gouge is 19.0 percent of the wall thickness. The pipeline is to be operated at 72.0 percent SMYS . Determin e whether or not it is necessary to repair the damage. The Youngs modulus is 30,000,000 1bain 2 The Charpy toughne ss (2/3 size)
IS
56 ftlbf
The area of the fracture surface of a 2/3 Charpy specimen is 0.083 in"
2.
BASIC EQUATION
D
I'
/
CCJ - K , J}] p ~ =~ COS-' [cxp{ l.5 JrE [Y(i_1.8D , )+ Y (100 2 R D")J-' cx [iI 1 a e :Ad 2R " t 2R K Jr
I
2
where:
Y,
=
(d) (d) 2 (d)' + (d)'
1.1 2 - 0.23 --; + 10.6 --;
- 21.7 --;
30.4 --;
r: Rev 2003/1
Page 12 of 15
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Y,
=
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tr 14tr
Ll2 - L39(~) + 732(~r -13
+
K , = 1.9 K,
= 057
(K 1 and K2 are non-linear regressio n parameters) Clf
hoop stress at failure (lbf/in2 )
(T
plastic collapse stress of infinitely long gouge (lbOin!)
A
frac ture Area of Charpy (0.083 in2 for a 2/3 Charpy specimen)
E
Young's Modulus (30,000,000 Ibflin2)
C.
2/3 Charpy toughness (ftlbt)
d
maximum or ave rage depth of part wall defect (in.)
Do
dent depth measured at zero pressure (in.) pipe wall thickness [in.]
R
outside radius of pipe (in.)
Rev 200311
Page 13 of 15
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WORKED EXAMPLE 8
ASSESSMENT OF DEFECTS IN A GIRTH WELD
1.
PROBLEM
A radiograph of a girth weld has revealed lack of sidewal l fusio n in thre e locations. Th ere arc no other defec ts in the weld. Th e pipe line is 6 lOmm (24") outside dia meter, 11.7 mm (0.460 in.) wall thic kness and grade X52. The ope rating pressu re of the pipeli ne i.. 70 bar ( 1015 psi). The defect data is as follows:
Start
End
Lack o f Sidewall Fusion I
02: 15
03:15
Lack o f Sidewall Fusion 2
03 :45
0·1:30
Lack of Sidewall Fusion 3
09:00
09:15
Use the EPRG Guideli nes on the Assessme nt of Defects in Transmission Pipel ine Girth Welds. Ass ume that all o f the requirement for the use of Tiers I, 2 and 3 are met.
Rev 2003 /1
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1 2 :0 0 (Top of Pipe)
Defect No.1 Defect No.3
9:00 - --+-
- - - --
- - - + - -- -- - - - -1--
6:00
3:00
(Bottom of Pipe)
Figure 1 - Sketc h of l.ocarion of Girth Weld Defect s
Rev 2003/1
Page 15 of 15
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WORKED EXAMPLE 9 SETTING EXPERT LEVEL CORROSION ACCEPTANCE CHARTS
1.
PROBLEM
An olTshore pipe line operator is thin king about using an intelligent pig on two o f his pipelines . This is because a new pipeline is being laid, and one of the older pipel ines has not bee n internally inspec ted for 8 years. The operator is thin king of having an inspec tion of the older pipel ine, and at the same lime would like to know if a ' basclinc-l' (or fingerprint) survey o f the new pipeline is worthwhile . Th e ope rator will be applying all the standard corrosio n prote ction and monitoring proce dures to the new pipeli ne. The existing pipel ine is 30 years old. A new, para llcl pipeline carry ing the same produc t (natural gas) is required beca use of increased demand. Th e new pipelin e will be identical to the existing line, in both geometry and in the product it carries. T he p roblems can be su mmarised as follo ws: I. The operator want s to know what the required hyd rotcs t press ure is, if the code requ ires him to test to 90% S ~lYS (based on the nomi nal wall th ickness and the mea n diameter)? 2.
Docs the operator need to run a pig in either of these pipelines?
3. Docs the operator need a baseline survey? -t. What is the size of co rrosion that can accept in these pipel ines?
5. Can an overall co rrosion inspection strategy he produced'?
The pipeline geo metry, material properties and operational parameter s arc as follow s: Ou tside diam eter , 0
500.2 mm (
No minal wal l thickness, t
12 mm
Corrosion allowance
1 nun
Minimum wall thick ness. tmin
I I mm
Material grade
X 65
Spec ified Minimum Yield Streng th
448
Pipeline operating pres sure, Pop
134 barg
Pipeline type
Seamless
Hydrot cst stress level
90010 SMYS
~1 Pa
4 A baseline survey is one carried out shortly atle r a new pipeline is brought Into service. It can reveal co nstruction and fabrication defec ts.
Rev 200311
Page 1 of 12
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The intelligent pig provider states that their pig can detect defects of depth 40% wall thickness. if the length of the defect is less than 3 times the wall thickness. If the defect is longer than this, then defects over 20% wall thickness in depth can be detected. The intelligent pig provider does not guarantee the detection of defects less than 7 mm in length.
2.
METHOD
1. Calculate the hydrotest p ressure:
The bydrotcs t pressure resulting in a hoop stress of 90% of Sl\.1YS is given by the follow.. ing equation (using the mean diameter and the nominal wall thickness):
p
=
207 D- I
where: P
hydrotcst pressure
a
hoop stress (equal to 90% SMYS) nominal pipe wall thickness pipe outside diameter
D
2. Catcutate cor rosion acceptance charts :
i. Stresses to be used:
For the purposes of this assessment. and to simplify the calculations. use the minimum wall thickness of 11 mrn when calculating the stresses at both the design pressure and the hydrorcst pressure.
ii. Failure model to be used: The Battelle failure criterion for a part wall defect should be used for the determination of the maximum tolerab le depth of corrosion. [The ASr>.1E R31.G Appendix , or other methods, could be used, but the following method will give similar answers]
I-(~ )
JI =
ii
=
I +0 26(
~ J'
1.I5S,IIYS
where: Pf
failure pressure
Rev 2003/1
Page 2 of 12
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Of
hoop stress at failure
M
bulging factor
o
flow strength
d
maximum depth of part wall defect
21..'
defect axial length
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pipe wall thickness R
outside radius of pipe
SMYS specified minimum yield stress
Note:
I. The ratio of defect depth to wall thickness (dJt) in the above equation can be replaced by the cross sectional area of the defect (A) divided by the area of the pipe wall occ upied by the defect , i.c. (A/(2e.t ». However, for a flat bottomed defect this reduces to (d.2c)/(t.2c), or tI/1. 2. A variety of different definitions of the Folias factor cxist.. 3. A variety of definitions of flow stress arc available, but in this case it is assumed that the flow stress is approximately 1.15 x SMYS.
The following calculations need to be performed: I.
Calculate the corrosion acceptance levels at the design pressure of 134 barg (using 11 mm wall thickness). Note that these levels will be failure levels, if simply using this pressure and the Battelle failure criterion.
2. Therefore, an appropriate safety factor must be added to the calculatio ns. 3. The easiest way to do this, is to work out the corrosion acceptance levels that would be used on the pipeline if it was working at the hydrotest pressure. This gives a safety factor (the levels give the size of defect that would fail at the hydrotcsr pressure). 4. The defect depth limits (i.c. the depth at which failure occurs) should be calculated over a range of defect lengths at the operating pressure (134 barg) and the hydrotest pressure. The results should be plaited in a graph or in a table.
Rev 2003/ 1
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WORKED EXAMPLE 10 DUCTILE FRACTURE PROPAGATION
1.
PROBLEM
A new natural gas pipeli ne is to be constructed. The pipeline geometry is 36 in. diameter, 12.7 mm (0.5 in.) wall thickness. grade X60. The design pressure of the pipeline is 70 bar. What full size Charpy impact energy should be specified 10 ensure that the pipeline has adequate toughness to arrest a propagating ductile frac ture? [Usc the Battelle equation]
2.
BASIC EQUATION
C.
= 1.5 x 2.382 x IO-, cr ,' ( Rt )'"-
where;
C.
full size Cha rpy V-Notch Energy, J
R
pipe radi us. mm
D
pipe diameter . mm
t
pipe wa ll thickness. mm
(71,
hoop stress. Nnun- 1
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TUTORIAL 11 DUCTILE FRACTURE PROPAGATION
1.
PROBLEM
Consider an existi ng natural gas pipeline. The pipeline geometry is 6lOmm (24") outside diameter, 9.52 mm (0.375 in.) wall thickness, grade X65. The minimum all heat average full size Charpy impact energy of the pipe (from the mill certificates) is 25 J (18ft lb). The ope rating pressure is 80 bar (1160p,i). Will the pipeline arrest a propagating ductile fracture? If not, to what level should the pressure be reduced? [Usc the Battelle equation]
2.
BASIC EQUATION
Cv = 1.5 x 2.382 x 10 -, rr '( II Rt )'" where: C,
full size Charpy V-Notch Energy, J
R
pipe radius, mm
[)
pipe dia meter, rnm pipe wall thickness, mm
all
hoop stress, Nmm-2
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Page 5 of 12
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WORKED EXAMPLE 12 HOW TO USE YOUR KNOWLEDGE OF FITNESS-FOR·PURPOSE, IN SETTING MAINTENANCE AND INSPECTION PRIORITIES.
You have worked on setting inspection level s for corrosion, and this wi ll bc of usc to you . However, how can you help with an ove ra ll inspection and maintenance plan'? How can you asses the benefits of an intelligent pig run with, say, a CP upgrade? A method for determining which inspection and maintenance metho d to usc, and 0 11 which pipeline, is a 'Prioriusation Scheme', These type of schemes arc increasingly being used to guide opera tors on the optimum usc of maintenance and inspection method s. For example, if a pipeline's major cause of dama ge is third party interference , incre ased surveillance or the introd uction of a One-Call Syst em may be appropriate preventative main tenanc e methods. However. if a pipeline is failing due to intern al corrosion, then an internal inspec tion using an intell igent pig would be appropriate.
PIPELINE PRIORITISATlON Overview PIPEU:\ E I.'... O R\I ATI O x
I
Int. corrosi on Ell.t Corrosion Fatigue Stress corrosion cracking Mechanica l damage Loss of ground support Thir d part)' intervention
SUSCl'Plibi lil~'
I
Fac tor
Risk 10 life Dama ge to property Loss of service Cost of failure Environmental effects
SeH' r it), Facto r
Probability
Conscqucnce
Relative risk
o f fail un:
I
PRIO RITY RATI:\G
of fa ilure
I
A Prioritisat ion Scheme considers the proba bility and con sequences o f failure within a group of pipelines (o r sections o r a single pipe line) by systematically assessing the pipelines' design, operation and failure h istory .
Rev 20 03/ 1
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Po ints arc allocated for desig n. operatio n and failure history. High points indicate high risks. For example. the probabi lity of failu re due to externa l corrosion is evaluated by considering the qua lity of the pipe coating. cr system. etc.. and the conse que nces of failure are considered by estimating the density of surroundi ng population. security of supply, etc. Our factors arc qualitatively assessed:
PRIORITISAnON Calculation -I Relative risk = Probability of failure x Co nsequence of failure -I Probability of failure = Sum of all (7) failure probabi lities. Ps -I Ind ividual probabilities = Susceptibility Factor (Su) x Severity Factor (Sv) -I Conseque nces of failure = Sum of all (5) consequences -I Relative risk 0; ( 117)( Su.Sv) x (1/5)(CO
PRIORITI SAnO N Susc eptibility & Seve r it y' ..J P ro bab ility of fa ilure depend s o n susccptib i lit y & seve rity ..J Fo r exa m ple. a p ipeline passin g throu gh heavily po pul a ted area.
is susceptih]e to thi rd party damage . If it is thin w alled . it wi ll re sult in severe dama ge ..J Fo r exam ple, a pipel ine w ith man y scam weld defect s (e.g . a
p ipe line that has fa iled a n um ber o f times 0 11 hyd ro tc st), is suscep tible to fat igue . bu t if the pipe line is no t pre ssure cyc led it w ill no t be sev ere
In this part icular Scheme we arc using 'severity' and 'suscep tibility' to g ivc us further information on the potential problems we may have 111 our line: The calculations are straightforward, but will rely hea.. . ily on knowledge and ex perience:
Rev 2003/1
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PRIORITISAnON Qllalltifj'ill~ Factors.... J Rank external corrosion a scale of 0 to 100 . j Take
into account parameters such as coating type (bare pipe. modem factory cooled, erc.), age & quality, CP availabi lity & efficiency & type, soil type.
J Rank past failure history 10 probability of failure in future J No failure to several/annum and increasing J Rank risk of mechanical damage J Remote (desert") pipe to a short length offshore pipe. in
busy shipping and fishing channel
The great advantage of this Prior itisation scheme is that it can: I.
rank all the pipeli nes within a grou p (or sectio ns of a pipel ine) in term s of probability of failure. and consequences of failure.
It.
determ ine which pipeli ne (or section of a pipeline) is most in need of some type of maintenance measure, and
11 1.
determine wh ich mainten ance measu re to lise.
There is now no need for a pipeline ope rator 10 'guess' which part of his system needs ma intenance. and he no w docs not to have wait for a section o f his system to show signs o f deterioration. The Priority Scheme is a proactive method o f setting maintenance and inspection schedule.
Rev 2003 /1
Page 8 of 12
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We'll now do a Worked Example .
PRIORITISATlON Calculation Score each parameter up to 100 sec
Susceptlbtllty
10
50
10
0
Loss of Third party Tol al ground in1~rv~mion ~urmorl 60 25 0
SC\'c r il)
10
SS
10
0
)0
25
0
100
27S0
100
0
1gOO
625
0
PRO IlABI \. r n
Int Corro,i\>n
Tot al
Exl Corro, ion
Fatig ue
~~~h"n i~a l
Damag e
5375.'7 76'
ro077')
Ri,k to life
[)amag~ prop~rty
CO:-;S f:Q lIf: i\n;S
10
'0 50
Lo"
of Cos t
01 Envi ronmental
failure
,~ rVKC
so
T01<1 1
effects
"
5
18515 37 (O.37)
Re lative risk = 0.077 x 0.37 = 0.028 1,
We'll consider 7 possible failure modes, and calculate their susceptibility and severity for a pipeline . Your tutor will describe the pipeline.
11.
We' ll then multiply our suscep tibility and severity ratings to give a total probability to r each failure mode.
111.
Hav ing calculated each ofthcse totals, we then add the m up to givc a total Probability
rv. \Ve now consider 5 possible consequences of failure. Again, we add these up to obtain our total consequence rating for the pipeline v,
If the numbers arc very big (c.g. > 10( 0) you can divide then by a common number, to make the numbers ' manageable' . Remember that the actual number doesn't matte r - it's how that number wil l compare against other pipeli ne rankings
VI.
Finally, we mu ltiply our Probability and Consequence together 10 obtain our ' relative risk' ranking for the pipeline.
V11 .
The above procedure is repeated for other pipelines, and therefor e all these pipelines can bc compared on the same q ualitative risk bas is.
viii. You can then sec how cha nging inspection and mainte nanc e procedure s can effect the risk ranking of pipelines, and how it changes their position relative to other pipelines .
r:
Wc'Ilnow do a Tutoria l:
Rev 2003/1
Page 9 of 12
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PRIORITlSATIOI\ Tlltorial ..J You are operating three pipelines: .J Pipeline I is 20". 0.375 ", crude oil, operating at 50010 smys, offshore. 35 years old. with a history ofleaks from internal corro sion. It passes throu gh environmentally-sensitive areas . .J Pipeline 2 is gas, 1 year old. 30", 0.75", but has failed at seam welds 5 times on the pre-service hydrotest. It passes through highly populated areas and operates at 30% S\ 1YS, and is heavi ly pressure
cycled. .J Pipeline 3 is gas. 36".0.5". 10 years old. tape wrapped. operating at 72% smys and has failed once by crackin g near a scam weld. but remote from compre ssor stations.
..J Perform a relative risk analysis
Here are so me expanded deta ils:
PRIORITl SATIOl\' Tutorial Data PIPI
PIPELINE 2 Jt,',
"
S'I ~t S S P" OIll 'M COATI!';, ; &
r IrE U:\ E I l ~·,~.J'j·
. ro old. o lf;hor,
I "".. oI.l.",,""'~,
""' '''"'' " ,W ~
C",J<
C",I
10 ... r< o ld. 110" , ", ..
30' .. ",»
j ' ~',.. m ),
n
r IPEUI' E 3 w.os-
~ : ~.
'or.,. ,,,"
n..
t'~ 1 , 1""'~'
N
SH'UU n ot Sl I'Pl Y
. ....IId_.. . -.-
Sf·('l 'RITl
:-;0,.-
Lo<.ol _ _ """.
{'P .. U K
["",nOlO.. ... 'R R\
'>t,- 'J' II-'-,,'CI' IHSTORY
1 .011
\ 1 " " I II ~ ro R Y
n ;n :RI· OPl'RAn o ~
,~
,
."
~
-.
-
- . . . 10<;,1..,· .1IMo, ]0 . .,.. ......
ho
10
' (.,10= d"" 00'0'- <"'''''"'' ,' d,,,,
'*-
s<.ml
f,,'o""
-
;=.>t"",.
0)'1<"'''' ~ .,," to " '" " " ,,".m.1
\\' ;11 b< p"'"",,, 'l' k.,').... ~.
r d ro.-lIollO .......
.~
!>e'",,,,
In
~
••
~
\1...,,,_ ·s "'1"""
~
h,.d<" t."
.m,..
-~-
~~
,,, ,,' <,
There are no differences
Rev 2003/1
R_b..o~lO l'IuudoIof
1k."J. popola'«l
--
....... ... 1"..,...- ,.._ 4 .. _
J<,;!<" ., ,,, .. of 7l %
'''''"'''(>l
(", .. OK
-...
~ ILL-\..' ~ ~
r...,
T'f'<' ",np""d
P 1""1')01<0'
cp .. ()t;
l .. \ l RO' ' '., ~' I
"" ,"" , ~ ,
l
~ ; "~I< f"I"". 'ho,"~"'
'"~ Kl'
~t .. ,m"m """ ",II b< ",,",.'ao.e
1"''' .''
~
any other parameter
Page 10 of 12
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You shou ld now be able to compare these pipe lines, and determine the pipeline that you most need to spend time and money on.
Therefore. Rank your pipel ines in the order 1,2,3.
PRIORIT SATIO N Tutorial- pipeline 1 In I C orr o,io n
1'1l0H"'H l t I T~'
r, I C o ,,,,, ioo
Fali gu"
s r,
M ccha nioa I
of
1. 0" g roun d ,u n o "
D am a g "
T h ir d p o ny i n t,' ,,' o n l i o n
To to l
SUHep'ibi l i t ~·
T ota l
R .. k 10 l ifo
V.mago pr o po"Y
to
Lo"
of
« ,,-i,"
of
CO " fail u r e
Lnv iro "mO"l a l " ff e ""
r ota1
CO'l;SEQt"F.~Cr.S
Rela t i v e ri s k PRIOR I TS AT IOl\ T ut o r i a/ - pipelin e 2 PR tlR ,tRII. IT Y
rot
" " ,'" ". ,
""
c ,,,",," O (" """,,n
n "" q '
of
1. " "
PO " n J
Th " d
r u t ,.
To . . ,
" " ' von,,,,"
'" P P" "
t o) 1.1
". m." ",oP_")
'" ,.L on" ",
of
Co>< f. ilo "
of
" " " , o" moo'"
l' 0 " l
< ffn"
c" "'Qr.'(:.' Rv e La
Rev 2003/ 1
f i
v e risk
Page 11 0112
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P R 10 R I T S A T 10 :'i T il t o r i u l - p ip e/in e J PRIJ U ,\ DI LIT Y
,,,
T,"
(' ," ''',",n (" "" ", ;u"
T " i ~".
sc c
M
l , o" ~
, ,," n d
"
•• . "
Suou p'ibill t y
T h i"r
r"'~
Ln', " .M''''''
T ot. I
S . , . . lt l
T . .. I
R"
~
to Itr.
I) . ... " . p,op."~
'.
L o ..
,u"'
.,
c."
h. lu '.
.,
t.ft ' '''' ... u
.. l
T oUI
.H«h
c o v v r c rr v c r s
R e la t i ,. e r i s k =
Rev 200311
Page 12 of 12
