Petroleum Development Oman L.L.C.
Unrestricted Novemer !00"
Document ID: SP-1190 #ilin$ %e&:
Design for Sour Service Specification
%e&'ords: H2S, Sour Gas, Design, Specification, Layout, Classification
This document is the property of Petroleum Development Development Oman, LLC LLC !either the "hole nor any part of this document may #e disclosed to others or reproduced, stored in a retrieval system, or transmitted in any form #y any means $electronic, mechanical, reprographic recording or other"ise% "ithout prior "ritten consent of the o"ner
Authorised for Issue:
Signed& ''''''''''' (nton Slui)terman, *+P CDH - Process +ngineering
The follo"ing is a #rief summary of the most recent revisions to this document (ersion No. ./
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Date )ut*or Septem#er (C Slui)terman 2/// *+P0. !ovem#er (C Slui)terman 2//4 *+P
Scope+,emars PDO1+D1/31/4 re"ritten to ne" format Definitions clarified evalidated and updated references
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INTRODUCTION................................................................................................................................." 5(C6GO*!D4 P*POS+ (!D SCOP+4 CO8PL9(!C+ :9TH TH9S SP+C99C(T9O!4
GENERAL GUIDELINES.................................................................................................................. +;POS*+ ++CTS (!D CH((CT+9ST9CS < D+S9G! PH9LOSOPH= O SO* S+>9C+<
SOUR SERVICE ACILIT! CLASSIICATION............................................................................/ G+!+(L? (C9L9T= CL(SS99C(T9O!? CL(SS99C(T9O! POC+D*+?
DESIGN RE#UIRE$ENTS TO %REVENT &2S RELEASE........................................................ P9P9!G@ S(8PL9!G S=ST+8@ >+!TS (!D D(9!S@ +A*9P8+!T3 OT(T9!G 9 !ST*8+!TSB
DESIGN TO $INI$ISE EECT O &2S RELEASE.................................................................10 :+LL O9+!T(T9O! ./ L(=O*T./ H2S D+T+CT9O! .. CO!TOL OO8S.7 D9SPOS(L O SO* G(S.7
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%!RO%&ORIC $ATERIALS.......................................................................................................... 1
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RELATED *USINESS CONTROL DOCU$ENTS..................................................................... 1"
A%%ENDI+ A: GLOSSARY OF TERMS, DEFINITIONS & ABBREVIATIONS..................................1
Design for Sour Service Specification
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I,trodu-tio,
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*-/rou,d
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9n a significant num#er of cases, produced hydrocar#ons contain hydrogen sulphide in sufficient concentration to pose a potential haard to personnel and euipment The production, transportation and treatment of these hydrocar#ons reuire special care in the design of the euipment and the facilities The operation, maintenance and surveillance shall #e such as to prevent a potentially haardous situation from developing Should such a situation nevertheless occur, the practices should assure the early detection and rectification of the potentially haardous situation The Shell HS+ manual on H 2S in Operations $+P B<1/7.@% provides a good overvie" of the sour service haards considerations
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%urose ,d s-oe This document specifies the design reuirements for facilities designated as Sour Service The scope includes& Characteristics and haards of H2S acilities classification Design reuirements to prevent H2S release Design to minimise H2S release Pyrophoric materials • • • • •
The classification reuirements of this specification shall #e applied retroactively The specification does not cover the reuirements for material selection or materials testing techniues
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Coi,-e 4ith this se-ifi-tio, The user shall o#tain "ritten approval from the Corporate unction Discipline Head $CDH% Process +ngineering for any deviation from this specification
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Design for Sour Service Specification
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Ge,er uidei,es
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E5osure effe-ts ,d -hr-teristi-s
Version 2.0
The eEposure effects and characteristics of hydrogen sulphide are descri#ed in the HS+ 8anual +P1B<1/7.@ The Fey effects are summarised #elo"& Concentration in air . ppm ./ ppm
2// ppm
233ect
Odour or rotten eggs can #e clearly detected *npleasant odour Possi#le eye irritation This is the long term eEposure limit The sense of smell "ill #e lost rapidly and it "ill irritate the eyes and throat Prolonged eEposure $2/ to 7/ minutes% may cause irreversi#le pulmonary oedema, ie accumulation of fluid in the lungs *nconsciousness after short eEposure, #reathing "ill stop if not treated uicFly Diiness, loss of sense of reasoning and #alance >ictims need prompt artificial ventilation and0or cardiopulmonary resuscitation techniues
H2S is highly solu#le in #oth "ater and oil "hich ena#les it to #e carried in solution for considera#le distances from a place of origin to escape in uneEpected areas
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Desi, hiosoh6 for Sour Ser7i-e The Haard and +ffects 8anagement Process $H+8P% should #e applied to the consideration of H2S throughout the design process and facility life The process consists of four #asic steps& $.% 9dentification $2% (ssessment $7% Control $4% ecovery The H+8P approach, and tools to assist its implementation, are descri#ed fully in +P B<1/7// 9n relation to H2S, the principal aspects to #e considered are & $.% 8inimising process stream H2S levels (t concept and front end design stages, process selection should seeF to minimise H2S levels, and avoid generation of process streams "ith very high levels of H2S $2% +nsuring that risFs associated "ith H2S are uantified and recorded The process of facility classification is discussed further in section 7 $7% 8inimising eEposure of operational and maintenance personnel to H2S risF, eg #y designing for unattended plant operation and minimum maintenance reuirements $4% +nsuring that detailed design minimises the risF of H2S release $<% +nsuring that adeuate personnel protection is provided This includes consideration of training, access control, gas detection, personal protective euipment and escape
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Design for Sour Service Specification
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Sour ser7i-e f-iit6 -ssifi-tio,
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Ge,er ( risF assessment methodology has #een developed for use in determining the H2S Classification of all PDO Production facilities $ref eport T0//.0B4 H 2S isF (ssessment 8ethodology and Classification of PDO Production acilities, Sept .BB4% This methodology has #een adopted #y this specification and shall #e applied during the design and operational phase The re1assessment reuirements during the operational phase are covered #y the Hydrogen Sulphide 8anagement procedure, P1./@3
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-iit6 -ssifi-tio, The production facilities shall #e assigned to one of three categories, depending on the concentration of H2S in the gas phase, resulting from reducing the process fluid or process gas to atmospheric pressure& / to 4B ppm S"eet facility
acilities shall #e classified as High isF Sour i f #oth& the concentration of H2S in the gas phase, resulting from reducing the process liuid to atmospheric pressure, eEceeds
•
or gas release only, an empirical relationship #et"een process stream pressure and H2S concentration has #een esta#lished "hich ena#les the determination of "hether a 2// ppm H2S concentration eEists at 2m distance "ithout individual gas dispersion calculations, as follo"s& P J C K .,///,/// "here& P concentration of H2S in the gas phase, resulting from reducing the process fluid to atmospheric pressure C process stream pressure $FPa $g% % or liuid or miEed phase release, individual dispersion calculations shall #e performed
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Cssifi-tio, ro-edure During the design phase, the process engineer shall uantify H2S concentrations and identify the points on the facility "here highest concentrations are anticipated to occur 9f concentrations greater than
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Desi, re8uiree,ts to re7e,t &2S reese The follo"ing guidelines shall #e follo"ed "here a facility is classified as High isF Sour or Lo" isF Sour, to minimise the pro#a#ility of H2S release (ll design considerations should consider the potential for the increase of H2S concentration in process streams over the life of the plant and the pro#a#ility that the classification may change from Lo" isF to High isF Sour over the production life cycle
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%ii, To minimise corrosion, piping should #e designed and installed in such a "ay that dead ends and areas of intermittent flo" are eliminated Dou#le #locF and #leed isolation shall #e provided for High isF Sour facilities Scre"ed fittings shall not #e used in Sour Service langes on piping in Sour Service should #e minimised "herever practical, to reduce the num#er of potential leaF sources 8aterial selection for sour service is addressed separately in +D1/31/2
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Si, s6ste The location of sampling points necessary for future monitoring of facility classification, as per section 7, shall #e determined in consultation "ith Operations during design Samples should #e taFen from the areas of process plant eEpected to contain the highest concentrations of H2S Typically 7 sample points "ould #e eEpected to cover high, lo" and atmospheric pressure levels :here posi#le these sample points have to #e com#ined "ith sample points for other purposes Details of sample points shall #e determined in consultation and agreement "ith Production Chemistry Department, to ensure compati#ility "ith local sample handling facilities Closed system #om# sampling systems shall #e used in High isF Sour service The use of #om# sampling in Lo" isF Sour service should also #e considered "here there is a high Gas Oil atio Sample return lines should #e routed #acF into a lo"er pressure process stream :here this cannot #e achieved the sample return line shall #e flared or vented
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Ve,ts ,d dri,s Depressurising of euipment and process lines in Sour Service should #e to a flare system :here this is not possi#le, venting may #e allo"ed #ut shall #e designed such that personnel cannot #e eEposed to H2S concentrations a#ove ./ ppm Special attention should #e paid to the vents from Glycol egenerator vapour outlets, "hich may contain very high levels of H2S (ll liuid in sour service shall #e piped into a closed drains system, "hich shall #e in accordance "ith specification SP1..2? >ents and drains, "hich are for hydrotesting shall have their outlets #locFed1off #y #lind flanges
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Design for Sour Service Specification
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Rotti, e8uie,t This section provides a checFlist for rotating euipment in Sour Service ( PDO rotating euipment specialist shall #e consulted for all rotating euipment specifications
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C2N4,I#U5)L CO6P,2SSO,S
The design shall #e in accordance "ith D+P 7.2B4/7/1Gen and D+P 7.2B?/721Gen S*a3t seals
The follo"ing mechanical seal types shall #e considered& $a% Dry gas seals $most preferred% for design pressure #elo" .2/ #ar $#% Conventional oil film seals for design pressure a#ove .2/ #ar $c% 8echanical seals $restricted #y speed0pressure% used typically in refrigeration systems and small machines Dry gas seals shall #e provided "ith a s"eet #uffer gas $eg nitrogen% Luricatin$ and seal oil s&stem 3or aove 1!0 ar s&stem.
( com#ined lu#ricating and seal oil system may #e used unless the process gas contain levels of H2S greater than ? mole M, "hich cannot #e adeuately removed #y a sour seal oil reclaimer 9f the H2S concentration is greater than ?M, then separate lu#rication and seal oil systems shall #e provided Seal oil collected in the contaminated seal oil trap shall not #e recycled Such oil shall #e reclaimed $vacuum degassing or air stripping% #efore re1circulating or #e discarded Seal vent
( seal leaF detection system shall #e installed Seal vent gas shall #e directed to (P flare 9f an (P flare system does not eEist, then local venting may #e allo"ed eciprocating compressors seal leaF detection system shall #e installed 5lanFet gas shall #e used for distance piece venting >ent gas shall #e discharged to (P flare 9f an (P flare system does not eEist, then local venting may #e allo"ed Distance piece venting and draining shall #e in accordance "ith D+P 7.2B4/7.1Gen The compressor vendor shall provide $as part of the documentation pacFage% process engineering flo" schemes of lu#ricating and seal oil systems, seal gas and flare and drain connections "hich clearly sho"s ho" the a#ove sour service reuirements have #een incorporated into the design ".".!
5as turines and $as en$ines
Sour gas should not #e used as fuel gas "herever possi#le 9f sour gas is used then& $a% Tur#ine engine materials and pipe"orF shall #e compati#le "ith the sour fuel $#% DupleE filters shall #e installed on the fuel gas inlet to ensure removal of ferrous sulphide $fine #lacF dust% These filters shall have "ater1flushing connections to avoid auto1ignition of pyrophoric iron "hen they are opened $c% uel supply shall #e superheated to vendor specification $d% Tur#ine enclosures shall #e ventilated to ensure a safe "orFing atmosphere $e% StacF height shall #e determined #ased on dispersion of eEhaust gas to ensure that ground level concentrations of SO2 do not eEceed < ppm
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Centri3u$al and positive displacement pumps
9f High isF Sour gas can #e released in the event of a seal leaFage, a seal leaFage detection device should #e installed 9f Lo" isF Sour gas can #e released in the event of a seal leaFage, consideration should #e given to installation of a seal leaFage detection device This device may #e a seal pot "ith a level s"itch or pressure transmitter "ith s"itch, vented to an (P flare The dou#le seal reuirement for the centrifugal pump shall #e governed #y D+P 7.2B/27/1Gen
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I,strue,ts Sour gas shall not #e used as instrument gas Pneumatic instruments in Sour Service shall use instrument air or s"eet gas
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Desi, to i,iise effe-t of &2S reese The follo"ing guidelines shall #e follo"ed to minimise the effect of an H2S release
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9e orie,ttio, :ell site access roads should, "here possi#le, #e located up"ind of prevailing "inds to minimise eEposure risF to personnel approaching them
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L6out 9n selecting a facility site, consideration should #e given to taFing advantage of the prevailing "ind direction, climatic conditions, terrain, transportation routes, and the proEimity of populated or pu#lic areas Clear entrance and eEit routes should #e maintained and confined areas "ithin the facilities should #e avoided Location, spacing, and height of flares or vent stacFs should #e determined #ased on accepta#le gas dispersion calculations
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Plant la&out and spacin$
or plant layout and spacing refer to PDO SP1..2@ 9n addition to this specification the follo"ing design criteria shall #e follo"ed Gas containing H2S may #e heavier or lighter than air, and so can accumulate in lo" or high places (reas of restricted ventilation $#oth high and lo"%, therefore, should #e avoided, so as to allo" sour gas releases to disperse +uipment handling sour fluid shall not #e placed inside a totally enclosed area The seals of rotating and reciprocating euipment "hich are a potential cause of High isF Sour releases shall #e given special consideration in plant layout and spacing to avoid trapping high concentrations of H2S and to taFe fullest advantage of the natural atmospheric dispersal effects (ll "orFing locations should #e euipped "ith at least t"o escape routes in separate directions These shall #e located as far apart as possi#le Locations "here operators maFe routine inspections for H2S release should #e easily accessi#le "hen "earing a compressed air #reathing apparatus +levated platforms shall use stairs only so that there is no hindrance "hen carrying #reather sets or rescuing H2S affected personnel .!.!
#ences
ences referred to in this document are all to stop personnel accidentally entering H2S areas The H2S concentration at the station fence during normal operation shall not eEceed ./ ppm Dispersion calculations shall #e performed for all normal or operational vents High isF and Lo" isF Sour "ellheads located in predominantly Ns"eet fields shall #e fenced Pipelines and flo"lines in sour service do not need to #e fenced .!.
2mer$enc& escape e7its
+mergency escape eEits in Lo" isF Sour and High isF Sour facilities shall #e provided such that escape is possi#le up"ind of $or at "orse, perpendicular to% the prevailing "ind direction (s a minimum, escape gates shall #e provided on opposite sides of the facility
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Design for Sour Service Specification
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8arnin$ si$ns
+ach facility designated as #eing in Sour Service shall have a "arning sign $in #oth +nglish and (ra#ic language% indicating "hether it is classified as High isF Sour or Lo" isF Sour in accordance "ith +D13B1/. The follo"ing signs $as detailed in +D13B1/.% are applica#le&
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.//7(&
Lo" isF Sour Service acility Sign
.//75&
High isF Sour Service acility Sign
:S //4&
H2S Haard :arning Sign
8indsocs
+ach Sour Service designated facility shall have sufficient "indsocFs located so that they may easily #e o#served from any position "ithin the station .!./
)sseml& points
The preparation of a comprehensive +vacuation Plan, including consideration of reuirements for assem#ly points, shall #e incorporated in the design of all High isF and Lo" isF Sour facilities (ssem#ly points shall #e located such that the local H2S concentration during the "orse credi#le accidental hydrocar#on release does not eEceed ./ ppm :here this "ould result in an assem#ly point location at an eEcessive distance from the facility $"hich might create additional pro#lems of access and communication%, a relaEation to a local concentration no greater than
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&2S Dete-tio, The primary o#)ective of fiEed H2S detection is to provide a "arning to prevent entry of personnel into a Fno"n haardous area ( fiEed system does not in itself provide personnel protection and shall not #e considered a su#stitute for entry precautions, personal H2S detection or personnel protective euipment ( iEed Detection system should #e provided around all process plant facilities classified as High isF Sour Consideration should #e given to installation on Lo" isF facilities as part of the overall facility safeguarding philosophy efer to HS+ 8anual +P1B<1/7.@ Section 4. for further guidance on the selection and design of H2S detection systems
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Design for Sour Service Specification
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#i7ed detectors in open air
There are t"o approaches that can #e applied to fiEed H2S detection in open areas& .% H 2S LeaF Detection ( sensor is installed to detect leaFage from a single source "here the H 2S concentration in the fluid is relatively high and 0or there is a relatively high pro#a#ility of a leaF This may #e applied on euipment for "hich an alternative design measure to minimise the pro#a#ility and0or uantity of a release, or to direct it to a safe location, is not readily availa#le 2% H2S (rea 8onitoring Sensors are installed to detect H2S dispersed into the plant area from any source, and thus also cover less liFely sources of release This system may #e applied in areas "here the installation of individual detectors for each potential source cannot #e ) ustified (ll fiEed detectors shall have a range of / 1 2/ ppm, and shall alarm at ./ ppm ..!
#i7ed detectors in enclosed areas
5uildings and enclosures "here personnel can enter during normal operations $eEcept "ell cellars%, located ad)acent to or in High isF Sour or Lo" isF Sour designated facilities, shall contain fiEed H2S detectors set to activate alarms at ./ ppm or control rooms and other #uildings "ith central air conditioning systems, "hich duct the chilled air throughout the #uilding, one fiEed H2S detector shall #e installed in the air conditioning inlet The air conditioning unit shall #e shutdo"n on H2S detection or High isF Sour facilities, gas tight dampers should #e installed on the inlet to the air conditioning unit, to close on detection of H2S or #uildings "here the air conditioning system does not duct air throughout the #uilding $such as standard gathering station control rooms%, fiEed H2S detectors shall #e installed one inside the main entrance and others in the principal rooms $eg the control room and the rest room% ..
)larms
iEed H2S detectors shall alarm audi#ly and visually at the& $.% Station control room panel $2% 8ain entrance to the station $7% H2S detector location $4% emote monitoring centre, if telemetry is installed The alarm shall also #e audi#le throughout the facility under all normal operating conditions These detectors should #e designated for H2S alarm only, and should not normally #e connected to the plant shutdo"n, due to the risF of spurious shutdo"n Consideration may #e given to a shutdo"n action on H2S detection for High isF Sour facilities, as part of an overall Safeguarding Philosophy The alarm accept #utton shall #e on the station control room panel This alarm shall #e distinguisha#le from the station fire alarm On acceptance of alarm at control room, only the audi#le alarm in the control room should silence the visual indication should remain on (t other locations #oth audio and visual alarms shall remain on till H2S level comes do"n #elo" the acceptance level Porta#le H2S detectors #oth electronic and manual devices $"ith small hand pump% are used for H2S detection
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Co,tro roos Control rooms shall #e designed in accordance "ith PDO1+D17/1/4 or Sour Service designated facilities the additional reuirements are &1 $.% (n oEygen resuscitator and spare O2 #ottle shall #e retained in each control room $2% (t least three "all mounted self1contained #reathing apparatus sets for emergency use shall #e installed in each control room These shall #e of at least 7/ minutes duration The a#ove resuscitator, spare O2 #ottle, #reathing apparatus sets and porta#le H2S detector, shall #e supplied as part of the control room pro)ect
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Disos of sour s Sour gas that is to #e disposed of in normal operation shall #e flared lare systems shall #e designed in accordance "ith D+P 3/4<././1Gen The elevation of the flare stacF and the fencing at the #ase shall fulfil the follo"ing criteria& $.%
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%6rohori- teris Pyrophoric iron sulphide can #e formed on the internal surfaces of car#on steel euipment containing H2S 9ron oEide present on the internal surfaces "ill react "ith the H 2S and form pyrophoric iron sulphide Pyrophoric iron sulphide can form even at very lo" H2S concentration $Q /. ppm% as long as the partial pressure of H2S eEceeds the partial pressure of oEygen in the environment >arious engineering options may #e considered to tacFle the iron1sulphide pro#lem, for eEample, use of coated pipe to avoid iron1sulphide formation, use of filters or cyclone separators at the station inlet to remove iron1sulphide fines, freuent pigging to Feep the pipe line clean of iron1 oEide, etc (ny one of these options may #e incorporated into t he design :hile specifying the filter specification the particle sie to #e removed should #e specified depending on the service reuirement 9f a filter or cyclone separator is used to remove iron1 sulphides, "ater1flushing connection shall #e provided to avoid auto ignition "hile removing the pyrophoric de#ris HS+ manual +P B<1/7.@ shall #e consulted to determine the procedure for handling pyrophoric iron sulphide
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Reted *usi,ess Co,tro Do-ue,ts PDO usiness Control Documents
Numer
Preparation Plant Design 8anual
+D1//1.2
8aterials Selection for Sour Service
+D1/31/2
Signs and Sign#oards
+D13B1/.
Hydrogen Sulphide 8anagement
P1./@3
9solation of Process +uipment Specification
SP1..2<
Drain Systems Specification
SP1..2?
Plant +uipment Layout Specification
SP1..2@
9dentification of On1Plot Pipe"orF Specification
SP1..??
S*ell Standards and 6anual
Numer
Centrifugal Pumps
D+P 7.2B/27/1Gen
Centrifugal Compressors
D+P 7.2B4/7/1Gen
eciprocating Compressors
D+P 7.2B4/7.1Gen
otary Type Compressors
D+P 7.2B?/721Gen
Piping Classes 1 5asis of Design
D+P 7.73/../1Gen
Piping General euirements
D+P 7.73/...1Gen
Design of Pipeline Pig Trap Systems
D+P 7.4/./.71Gen
Pressure elief and lare System
D+P 3/4<././1Gen
HS+ 8anual, Overvie"
+P B<1/7//
HS+ 8anual, Hydrogen Sulphide $H2S% in Operations
+P B<1/7.@
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Design for Sour Service Specification
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Ae,di5 A: Glossary of Terms, Definitions & Are!iations (P CDH D+P +D H+8P H2S HS+ PDO Ppm SO2
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(tmospheric Pressure Corporate unction Discipline Head Design and +ngineering Practice +ngineering eference Document Haard and +ffect 8anagement Process Hydrogen Sulphide Health, Safety and +nvironment Petroleum Development Oman LLC Parts per million Sulphur DioEide
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