Tan k In s p ec t i o n Techniques
Ult ltra rason sonic ic Thic hickne kness ss of the Shell
Raw Shell Thickness Data
Averaged Thickness Data over Lc
z
Magnetic Flux Leakage z z
z
Coil Sensors Hall Effect Sensors
Technology adapted from Smart Pig Technology
MFL Tank Inspection
Distribution of Flux in a Plate With a Soil Side Defect
Types of Sensors z
Coils z
Passive Devices
z
Faradays Law
z
Measures Change in the Flux Field
z
Speed of Scanning is Important
Types of Sensors z
Hall Effect Sensors z
Solid State Device
z
Absolute Magnitude of Flux Density
z
More Sensitive
z
More Noise
z
Temperature Sensitive
Calibration z z
Manufacturers Recommendations Simulate Tank Conditions Coating z Plate Thickness z Temperature z Material Properties z
z
API 653 Appendix G
Tank Surface Preparation
“What an inspector cannot see can’t be effectively inspected.” Additionally, items such as vacuum box inspections are severely compromised if tank bottom and weld seams aren’t properly cleaned.
The visual portion of the API-653 inspection is critical.
The following are typical examples of what we encounter:
Here are some examples of good surface preparation using either brush blast or ultrahigh pressure water:
Limitations of MFL Scanners z
Bottom Plate Lap Welds
z
Weld Tacks
Limitations of MFL Scanners
•Shell •Surface Condition
Limitations of MFL Scanners
z
Plate Curvature
Change in Plate Thickness A thinner plate causes more flux lines to appear above the plate
Defect Orientation
Defect Orientation
Keys to a Good Inspection z
z z z
Well trained, experienced inspectors/operators Proper cleanliness of tank floor Understand limitations and plan your options Proper equipment
Late 1994 – 1995 Industry Conducted a “ PERF” Study on MFL/MFE Floor Scanning Equipment Results 1. Identified a few obviously inferior pieces of equipment, but…the key finding was “the Major Factor in a Quality MFL/MFE Inspection was the Inspector/Operator”by a wide margin. A couple of key major oil companies began testing “qualifying” 2. inspector/operators. 3. API has now moved toward testing and will offer a certification program based upon Appendix G.
Training and Certification Continued z
z
ASNT, Level II Ultrasonic Training and Certification Know Your Vendor’s Training and Certification Programs a) Ask for internal documentation b) Require in your purchasing process Appendix G. basic certification c) Rely on specialists – J ust because someone can operate a D-meter and has an API 653 certification does not mean they know tanks
Conclusion z
MFL has physical limitations
z
Successfully used for inspections every day
z
Scanner Operator should understand limitations
U.T. Prove-Up of Tank Bottom
z
z
Use Ultrasonic Thickness to determine remaining thickness of bottom indications. Flaw dectector to size defects and other anomalies.
SLOFEC (Saturated LOw Frequency Eddy Current)
SLOFEC Corrosion testing of material thicknesses up to 35 mm and more z Much higher detectability than conventional MFL techniques, especially on thicker walls z Testing through surface coatings of 8 mm and more z No physical coupling of the sensors z
Magnetic Particle Inspection
z
Consider z z
z z z z
Inside Corner Weld Outside Corner Weld Sump to Bottom Sump Welds Nozzles Reinforcement Pads
Leak Testing z
Vacuum Box Test z z
z
Bottom Lap Welds Bottom Repairs
Pressure Test z z z
Reinforcement Pads False Bottom Sump Tank Hydro Test
Helium Leak Detector
Helium Leak Detector Wand
Alternative Internal Inspection z
In-Service Robotic Inspection
In-Service Internal Inspections z
Sampling of tank bottom thickness z
z
Utilize Statistical Methods z
z
2 to 15 percent of the bottom inspected
Extreme Value Analysis
Not a substitute for an out-of-service inspection
Risk Assessment
Risk Assessment Considers both the Likelihood and the Consequences of Failure Risk Assessment is not a new idea, but has recently become more formalized
RBI Background z
z z z
1985 ASME was commissioned to create a “guidance document”– published 1991 1993 - API began development on RBI 2000 - API-581 - RBI (Base Resource Document) 2002 - API-581 Appendix O “Tank RBI”
Advantages of RBI z z
z
z z
(0.2.5.1)
Introduces a another scheduling option Consistent approach for calculating remaining life Consistent approach for determining Consequence of Failure Focus inspection effort to reduce Risk Improved record keeping
Risk Assessment Strategies Absolute Risk Attempts to Quantify the Actual
Probability of a Failure Type Relative Risk Calculates an Index Score Which Is
Compared to Scores of Other Segments
Ris isk k Ass A sse ess ssme ment nt
Relative Risk Is Equal to: Relative Probability Times
P erceiv erceived ed Con Cons sequ equences ences
Ris isk k Ass A sse ess ssme ment nt
z
Calculate relative probabilities of failure
z
Calculate perceived consequences
z
Calculate relative risk & rank segments
Relative Risk Assessment Components: •
Algorithm
•
Data
•
Software
Risk Assessment
z
Identify Possible Failure Modes z
z
Service History, DOT Incident Data, Experience
Identify Possible Consequences z
Public, Environment, Business
Risk Assessment Algorithms z
z
z
Failures causes can typically be classified Failures often result from the interaction of several factors Group the variables by failure mode and organize into an algorithm
Develop Algorithms
z
Data (Variables) z
What data are available
z
What data are relevant
z
What data need to be collected
Relative Risk Assessment z
z
Create variables that describe pipeline attributes Organize variables into an algorithm corresponding to failure modes
z
Assign weighting factors
z
Perform sensitivity analysis
Ranking by Relative Risk The risk is never zero
z
The more you do, the lower your relative risk
z
Basic Tank RBI Methodology
Three basic components:
z
z z z
z
Roof Shell Bottom
Looking for INDIVIDUAL Risk and COMBINED Risk
Example z z z z z
Roof = High Shell = Low Bottom = Low Combined Risk = High What can be done to reduce RISK?
Quantitative Analysis
(0.2.5.3)
Need to know “future risk” z Assume bottom corrosion rate and run calculator for different years z Tabulated this data into a spreadsheet z From the data list tanks based on risk z
Risk Matrix y r o g e t a C y t i l i b a b o r P
Consequence Category
Summary Tank Data Example
T-1
T-2
T-3
T-4
T-5
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
Btm
24
24
24
24
24
24
21
21
17
17
13
13
Shell
19
19
19
19
19
19
19
19
19
19
19
19
Roof
14
14
14
8
8
8
8
4
4
4
4
4
Btm
24
24
24
24
24
24
21
21
17
17
13
13
Shell
22
22
22
22
22
22
22
22
22
22
22
22
Roof
19
19
15
15
15
9
9
6
6
2
2
2
Btm
24
24
24
24
24
24
21
21
17
17
13
13
Shell
19
19
19
19
19
19
19
19
19
19
19
19
Roof
25
25
25
25
25
23
23
23
20
20
20
16
Btm
25
25
25
25
25
25
23
23
23
23
23
23
Shell
22
22
22
22
22
22
22
22
22
22
22
22
Roof
12
12
12
12
12
10
10
10
5
5
5
3
Btm
22
18
18
14
14
8
8
8
4
4
4
4
Shell
19
19
19
19
19
19
19
19
19
19
19
19
Roof
22
22
22
22
22
22
18
18
18
18
18
18
11
7
4
2
1
16
13
8
6
3
20
17
14
9
5
23
21
18
15
10
25
24
22
19
12
Required Data z
Design: z
Service, size, type, courses, year, new bottom, roof, years in service, diked, ……
Required Data z
Consequence: z
Fluid type, detection time, ignition source, environmental risk, spill area, inventory (lbs), date in service, effective age per component, pressure, potential release, bottom type…
Required Data z
Probability: z z z z z
Shell Int / Ext corrosion type / rate Bottom Int / Ext corrosion type / rate Bottom stock-side protection Roof condition Last internal inspection……..
Conclusions from Quantitative Analysis Had to create a judgment value for an analytical task z Adjusting the data will adjust the Risk z The bottom “corrosion rate”was the single biggest driver of Risk z Learned that the calculator is not a crystal ball. z
0.2.1
Nex t Tw o RB I Ty p es z
z
Qualitat ualitativ ive e – too sub subject jectiv ive e and and open to interpretation Combo Use the same basic analytical data Tank has a S econdary Con Containment z Tan z
L et ’ s Go Ba B ac k In Ti Ti m e Early 80’s A refinery realized they needed to know if they had a tank leakage problem Tried every technique known to man plus a z Tri few more to determine if a tank might be leaking z
Old Tank Bo Bott ttom oms s 60’ 0’s s applied applied F iberglas iberglass s z Up till 80’s very few bottoms were replaced Their analysi sis s showed that many of the F G z The bottoms may be leaking even after a good inspection z
Of 300 Tanks is One Leaking? z
z
Researched all forms of pipeline and tank testing / inspection. Developed the “secondary containment” bottom system.
How A Tank Leaks z
API-581 Appendix O z
99.72% chance the tank will “weep” before “leak”. (Table 2)
z
z
1983-1993 – 0.9% bottom leak
(Table 3)
After 20 years – Heavy oil some corrosion beneath coating – Finished none
Combination Conclusions z z
z
Weep before leak Bottom condition may be determined based on product type: Crude, Finished, and all others Beginning of learning curve
Conclusion z z z
z
Develop a methodology for Consequence Develop a written process Develop a process to “verify”your methodology Some tanks are eligible for RBI!
Similar Service
Similar Service Assessment:
What is Similar Service Assessment? The process by which corrosion rates and inspection intervals are established for a candidate tank using corrosion rates and other relevant service history from a control tank for the purpose of establishing the next inspection date.
Similar Service Assessment: Why Have a Similar Service Appendix?
To provide industry with performancebased guidance on conducting a similar service assessment.
Currently, there is no definition of similar service and no clear guidance on conducting a similar service assessment.
Similar Service Assessment: “If it looks like a duck, walks like a duck, and talks like a duck…
…then it’s probably a duck.”
Similar Service Assessment:
Similar Service Assessment:
How is a Similar Service Assessment Done?
Collect data for control and candidate tanks. Conduct assessment using Data Sheet from Appendix H. Determine if Similar Service can be used for candidate tank. Determine the corrosion rates to apply to the candidate tank. Establish the next internal inspection date for the candidate tank. Document internal inspection date for candidate tank. As additional data becomes available, validate corrosion rate established for candidate tank. Determine if additional inspection data changes the inspection date for the candidate tank.
Similar Service Assessment: Collect data for control and candidate tanks Conduct similar service assessment using data sheet Determine if similar service can be applied to candidate tank Determine the corrosion rate to be applied to the candidate tank Establish next internal inspection date for the candidate tank Determine if additional inspection data changes inspection date for candidate tank
Document revised internal inspection date for candidate tank Validate revised inspection date for candidate tank as additional information is available
Similar Service Assessment:
Control Tank Tank(s) for which corrosion rates and other relevant service history are known and documented.
Candidate Tank Tank for which corrosion rates are not known
Similar Service Assessment: CANDIDATE TANK(S) CONTROL TANK
900 Miles
Similar Service Assessment: Product Side
Side exposed to stored liquid or gas product
Soil Side Side exposed to supporting soil, concrete, or other material
Similar Service Assessment:
Similar Service Assessment Criteria
Year tank erected
Bottom material
Shell material
Corrosion allowance, bottom and shell
Bottom lining type, thickness and age
Cathodic protection
Similar Service Assessment:
Similar Service Assessment Criteria (cont’d) Double bottom? Soil material in contact with bottom plate Soil or material type pH, Alkalinity Moisture Salinity Resistivity Oil type (If oiled sand fou ndation) Soil /material cleanli ness Soil gradation Chlorides Sulfates
Similar Service Assessment:
Similar Service Assessment Criteria (cont’d)
Ambient conditions Current service conditions
Product classification Specific gravity of liquid Reid vapor pressure at 60 F Normal operating temperature Inert gas blanket, if used Water bottom, if used Sulfur content Length of time in service Product corrosivity
Previous service conditions
Similar Service Assessment: Similar Service Assessment Criteria (cont’d) Product classification Additional considerations
MFL or MFE data for tank bottom Ultrasonic thickness measurement data Fiber optic monitoring system data Cathodic protection monitoring tube data Tank bottom integrity testing data Maintenance procedures, including frequency and method of tank cleaning
Similar Service Assessment: TABLE 1.0 Classification
Description
Example
A
Low Sulfur Light Oils (<1% sulfur)
No. 2 fuel oil, diesel, kerosene, jet fuel, gasoline
B
High Sulfur Light Oils (>1% sulfur)
Unfinished heating oil, distillate
C
Sweet Sulfur Heavy Oils (<1% sulfur)
Heavy gas oil & sweet residual
D
Sweet Sulfur Heavy Oils (>1% sulfur)
Sour residual
E
Slops & Process Waters
See description
F
Finished Lube Oils
Automotive, diesel and aviation oil
G
Sludges
Acidic, non-acidic
H
Crude Oils
Light volatile oil (Class 1), Non-sticky oil (Class 2), Heavy sticky oil (Class 3), Non-fluid (heavy crude, high paraffin) (Class 4)
I
Additives
Gasoline performance additives
J
Solvents
Ketones, alcohol, toluene, xylene, glycols, glycol ethers
K
Chemicals
Phosphoric, sulfuric, hydrochloric, formic, and nitric acids
Similar Service Assessment:
Similar Service Assessment:
What is the Objective of the Assessment?
Establish corrosion rates and inspection intervals for a candidate tank using corrosion rates and other relevant service history from a control tank for the purpose of establishing the next inspection date.
The concept is shown graphically on the next slide…….
Similar Service Assessment: Tank was new in 1970 Original bottom thickness = 1/4” At 20 years, thickness = 0.05” Metal loss = .25 - .05 = 0.20” Corrosion rate = .2*1000/20 = 10mpy New 1/4” bottom installed in 1990 In same service*, the new bottom can be expected to corrode at the same rate, from which a retirement date can be calculated. * All other factors being equal
Similar Service Assessment:
Example of Use of Similar Service Assessment Data Sheet
Similar Service Assessment: Section 1.0 - Tank Bottom Product Side Assessment
Tank Characteristic
Control Tank
Candidate Tank
Match ?
Year Tank Erected
1984
1986
No
Bottom Material
A36
A36
Yes
Corrosion Allowance
None
1/16”
No
Bottom Lining Type
None
None
Yes
Bottom Lining Thickness Bottom Lining Age
N/A
N/A
Yes
N/A
N/A
Yes
Similar Service Assessment: Current Servi ce Conditions
Control Tank
Candidate Tank
Match?
Current Product Name
No. 2 Fuel Oil
No. 2 Fuel Oil
Yes
Product Classification
1
1
Yes
Specific Gravity of Product
0.87
0.87
Yes
Normal Operating Temperature
60 F
60 F
Yes
Water Bottom?
No
No
Yes
Sulfur Content
< 1%
< 1%
Yes
Time in This Service
10 Years
15 Years
No
Product Corrosivity
Mild
Mild
Yes
Similar Service Assessment: Previous Service Conditions
Control Tank
Candidate Tank
Match?
Previous Product Name
Gasoline
Diesel Fuel
No
1
1
Yes
Specific Gravity of Product
0.80
0.85
No
Normal Operating Temperature
50 F
60 F
No
Water Bottom?
No
No
Yes
Sulfur Content
< 1%
< 1%
Yes
11 Years
6 Years
No
Mild
Mild
Product Classification
Time in This Service P
d
tC
i it
Y
Similar Service Assessment: Section 2.0 - Tank Bottom Soil Side Assessment
Tank Characteristic
Control Tank
Candidate Tank
Match?
Year Tank Erected
1984
1986
No
Bottom Material
A36
A36
Yes
Corrosion Allowance
None
1/16”
No
Double Bottom?
None
None
Yes
Similar Service Assessment: Soil / Material Characteristics
Control Tank
Candidate Tank
Match?
Crushed stone & sand
Crushed stone & sand
Yes
Soil pH
6.7
7.1
No
Soil Alkalinity
No
No
Yes
Soil Moisture
15%
20%
No
Soil Salinity
Insignificant
Insignificant
Yes
Soil Resistivity
3500 ohm-cm
3000 ohm-cm
No
Diesel Oil
None
No
Some sulfate contaminants
No known contaminants
No
Soil Type
Oil Type – If Oiled Sand Cushion Soil Cleanliness
Similar Service Assessment: Current Operating Conditions
Control Tank
Candidate Tank
Match ?
Ambient
Ambient
Yes
Cathodic Protection
Yes
Yes
Yes
Ponding/Water
Yes
No
No
Control Tank
Candidate Tank
Match ?
Ambient
Ambient
Yes
Cathodic Protection
No
No
Yes
Ponding/Water
Yes
No
No
Normal Operating Temperature
Previous Operating Conditions Normal Operating Temperature
Similar Service Assessment:
Similar Service Assessment Conclusions:
Does this assessment include additional assessment documentation? Based on the criteria reviewed in this Similar Service Evaluation Is Or Is Not recommended for this tank. The corrosion rate to be applied to the product side of this tank is ______ mpy. Comments
Similar Service Assessment: Similar Service Assessment Documentation: THE DATA SHEET SHALL BE MAINTAINED IN THE RECORD FILE AS PER 6.8. ASSESSED BY:___________________ DATE:___________ APPROVED BY:__________________ DATE:___________ (tank owner/operator)
“ TANKPAC” - Condition Monitoring for Storage Tank Bottoms Acoustic Emissions
Information pr ovided by:
Tank bottoms are the only structural part of a tank with no access for inspection during operation
TANKPAC™ - In-Service Condition Assessment of Tank Bottoms Case Study for MHG Sales Growth ….A $2-7K Traditional NDT test that just became a $40-45K complete inspection package with zero competition
•Traditional NDT (Visu al and MFL after op ening • Ac ou st ic Emi ss ion TANKPAC™ •Complete API-653 • Au to mat ed Ul tras on ics (LSI) •Risk Based Inspection (RBI)
Failure of time-based maintenance Hot oil tank, 140 deg.C
Internally inspected 12 months prior to failure, including UT+MFL. This collapse was due to a narrow band of annular ring corrosion. When the ring split the very rapid loss of hot liquid pulled a vacuum collapsing the tank shell.
Failure of time-based maintenance 50m CRUDE OIL TANK
One of 40+ holes in the tank floor, although the tank was not leaking during service, only the sludge and debris were sealing the floor. Attempts to resuspend the sludge have resulted in major leakage on many occasions.
Failure of time-based maintenance Naptha Tank
Leaking 100 cubic metres per day through a 1cm hole. Operations noticed losses after a week, but no visible product, which was disappearing into ground. When the plates were cut the cavity under the floor was several cubic meters in size.
Failures of time-based maintenance z
z
z
z z
z
1mm diameter pinhole leak in a 25m diesel tank, where epoxy coating failed. Collapse of a 25m sulphur tank due to annular-to-shell corrosion. 200 cubic meters per day leakage in a 75m crude tank, 100 cu.m/hour in a 97m crude tank... Many more examples……. Tanks removed from service, cleaned, sludge dumped, tank inspected…...and no repairs required….. If time based internal inspection worked……. this would not be happening…....
Summary and Requirements z
Summary: z z z z
z
Access to tank floors for inspection is difficult and costly. Leakage is no longer environmentally acceptable. Risk of catastrophic failure with severe annular ring damage. Cleaning costs can be >$200,000, + environmental waste problem. >> If no repairs are required these costs are wasted <<
Requirements: z
z
z
To identify tanks which do NOT yet require internal inspection and repair, this prevents the waste of maintenance resources and protects the environment. To determine the relative condition of damaged floors so that a correct priority for internal maintenance may be set. To do the above with as little disruption to operations as possible.
“ TANKPAC” Development History z
z z z
z z
z
1989 PAL approached by customers, discussion on requirements for tank floor condition assessment. 1990 First AE trials on tank floors, Esso, BP, . 1992 User group formed, grew from 5 to 20+ Co’s. 1996 User group became part of EEMUA, ~30 Co’s (Engineering Equipment Material Users Association) experience now >600 tank floor tests, feedback on internal inspection of >150 tanks, procedure at rev.4. 1997 Procedure accepted by Saudi Aramco. 1998 Results of TANKPAC “correlation study”presented at ECNDT by Shell/Dow etc. >1000 tests now completed. 1999 EEMUA recommendations to members.
Basis of Operation •Corrosion of steel causes Acoustic Emission (Yuyama, Condello etc).
^Number of emissions
•This is detected by sensors on the outside of the tank. •Emission reaching three sensors is located. Shown right: one hour of emission from a tank with very severe corrosion, characteristics of emission change with scaling.
time Signal amplitude >>
Corrosion of Internal Zinc Anodes •Internal sacrificial anodes corrode in place of tank floor. •Zinc blocks can be 1m in size. •Oilfield production tanks use sacrificial anodes-very active until used. •Special procedures used to separate anode corrosion from floor corrosion.
Location of remaining active anodes
TANKPAC: outline procedure z z
z z
Tank is isolated and allowed to settle. Sensors are attached to the tank wall around the entire circumference, ~1m above annular. One row, or two rows where condensation or high noise is possible. The tank is monitored, duration is ~1-2 hours. The data is processed to eliminate unwanted noise. z
z
z z z
Note: effect of noise is conservative >increases grade.
The result is graded per procedure for the “overall”grade on an “A”(“good”) to “E”(“bad”) scale. Location of 3+hit sources by triangulation. Location and grading of 3+hit “potential leak”sources*. Discussion and recommendations. *Shell EWGAE paper
Sens nsor or Mou ount ntin ing g and and Cali libr bra ati tion on z
z
z
Sensors are mounted ~1m above bottom knuckle or above sludge. P aint aint smoothed or removed removed if not adherent. A pencil lead fracture is used for calibration. z
z
Thi This is detectable at up to 70 metres on large product tanks.
All sensors are checked after mounting.
Ac A c o u s t i c So Sou u r c es d et etec ectt ed z
z
Sources of interest: z Spalling of corrosion products. z Leak noise: flow interruption,or turbulence. Extraneous noise to be removed: z Roof movement noise. z Structural movement. z External and pipe-borne noise. z Condensation. z P article article impact impacts s. z Valve leakage.
Inp nput uts s t o Gr ade and and Recommendations z
“Overall” activit activity y level, “A”“A”-good good condition, “E”-bad condition, “B”, “C”, “D”, interm intermediate ediate condit conditio ions ns:: z z z
z
z
z
Diameter, product, sludge height. Normalise using: number of sensors, data filtered, threshold. Special procedures for sacrificial anodes, soft rubber lining.
Locate overall data: z The The ~5-30% which “hits” s”> >3 sen sensor sors, any concentrated sources? S eparate, eparate, locat locate, e, and grade grade “pot “potent ential ial leak” data: data: z More severe local damage, “A” A”tto “E” scale. Retest recommendation based on above factors.
Recommendations Matrix “Overall”Grade A
B
C
D
E
“PLD”Grade
4
4
2
(2)
(1) (n/a)
A
4
4
2
(2)
(1)
B
4
4
2
2
(1)
C
2
2
1
1
1
D
2
1
1
1
1
E
1
1
1
1
1
Clearly leaking tanks often unable to grade, (should be opened anyway).
Limitations z
Detects and grades active corrosion only.
Not suitable for assessing the internal condition of tanks which are cleaned mechanically or chemically as this “resets”the condition, (underside OK). Use history!! Small leaks may be masked by active floor corrosion. Large leaks will mask overall floor condition. Activity from active corrosion under insulation may mask floor condition. Location may be unreliable on very active D/E tanks due to simultaneous sources, (the tank needs opening anyway!). Not all tanks can be tested, due to noise/condensation etc. Complex procedure requires extensive training + control. z
z z z z
z z
Quality Control and Training z
Documentary quality control system under ISO 9002: z z z z z
z
Engineer training and certification: z z z z
z
Trained and certified engineers. Controlled TANKPAC procedures. Controlled TANKPAC Field worksheets . Quality plan for each test. Digital storage of data and full traceability. ASNT II general AE TANKPAC procedure class and field training. TANKPAC written and practical examination. TANKPAC minimum experience requirement (~50 tanks).
PAC level III review of and approval of report.
Overall AE Grade vs. % of tanks for crude and product tanks from major sites 45 40 35 30 25 20 15 10 5 0
% of tanks
ALL SITES IN SURVEY sample size 598 tanks 6/96 %CRUDE %PROD. %ALL
A
B
C
D
E
TANKPAC GRADE
Reliability: TANKPAC “ overall” grading versus repairs required* * P.van de Loo/Shell, B.Hermann/Dow, ECNDT 1998 Follow-up results versus AE-grades, normalised per AE-grade population of 157 tanks (Shell, Dow-Stade, DSM, PKE, Total and P AL database)
120 100 ) 80 % ( e v i t 60 a l e R
40 20 0 A
B
C
D
E AE-grade
FU 1/2 Minimal damage: no repairs FU 3 Damage: some repairs FU 4 Significant damage: major repair/new floor
Naptha Tank-Before: “ E” grade, and after repair: “ A” grade
3-D view of “ E” grade crude tank and damage found
110m GRP lined Crude Oil Tank: TANKPAC and MFL
Hot Fuel Oil Tank 50m z z z
z
“E”grade overall. Annular ring very active. Dug underneath annular ring in most active areas: Up to 8mm loss of metal on z 15mm annular plates Tank shut down immediately, avoiding failure (see next slide).
Leaking Naptha Tank z z
z z
z
100 cu.m/day loss No visible indication of a leak Faint smell only TANKPAC test at 2% sensitivity due to noise-2 mins. only: 1cm hole found at location shown
