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Aboveground Storage Aboveground Storage

Tank Integrity Seminar Tank Integrity SeminarReview of Review of

API Standard 653 API Standard 653

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History of API Standard 653History of API Standard 653

Three incidents focused the United State Three incidents focused the United State ss

attention on above ground storage tanksattention on above ground storage tanks

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Incident 2Incident 2

January 2, 1988, a 96,000 barrel Aboveground

Storage Tank in Pennsylvania failed. Thecatastrophic failure spilled about 1 milliongallons of oil into the Monongahela River.

The spill affected the water supply of millions of people and moved control of abovegroundstorage tanks to the top of the congressionalagenda.

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In 1988, a floating roof drain on a storage tank in

California failed and dumped about 1,000,000gallons of diesel fuel into a California waterway.

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History of API 653History of API 653

After the Ashland incident: After the Ashland incident:

Several congressional and state hearingsSeveral congressional and state hearings which cast doubts on the suitability of which cast doubts on the suitability of

aboveground storage tank constructionaboveground storage tank constructionstandards.standards. The hearings highlighted the fact that repair The hearings highlighted the fact that repairstandardsstandards did not exist.did not exist.

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API API s Storage Tank Task Forces Storage Tank Task Force

Review proposed state and federal legislationReview proposed state and federal legislationDevelop APIDevelop API s position on Relevant Issuess position on Relevant Issues

Conduct a tank universe study Conduct a tank universe study Quantify AST releasesQuantify AST releasesDetermine current industry practicesDetermine current industry practices

Judge the adequacy of current standard Judge the adequacy of current standardEnsure that the needed standards are producedEnsure that the needed standards are produced

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To respond to the need for industry standards for To respond to the need for industry standards for

AST ASTs, API elected to write 3 new standards.s, API elected to write 3 new standards. API RP 651 API RP 651 Cathodic Protection of AbovegroundCathodic Protection of Aboveground

Petroleum Storage TanksPetroleum Storage Tanks API RP 652 API RP 652 Lining of Aboveground PetroleumLining of Aboveground Petroleum

Storage Tank BottomsStorage Tank Bottoms

API Std 653 API Std 653 Tank Inspection, Repair, Alteration, Tank Inspection, Repair, Alteration,and Reconstructionand Reconstruction

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API 653 API 653 Section 1Section 1

This standard covers: This standard covers:

Carbon and low alloy steel tanks built to API Standard650 and its predecessor 12C.Provides minimum requirements for maintaining theintegrity of welded or riveted, non-refrigerated,atmospheric pressure, aboveground storage tanks

After they have been placed in serviceIt covers the maintenance inspection, repair, alteration,relocation, and reconstruction

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The scope is limited to: The scope is limited to: Tank foundationBottomShellStructureRoof

Attached appurtenances, andNozzles

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13

API 653 API 653

Suitability for ServiceSuitability for Service

Section 4Section 4

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Suitability For ServiceSuitability For Service

When the results of a tank inspection show that a When the results of a tank inspection show that achange has occurred from the original physicalchange has occurred from the original physical

condition of that tank, an evaluation shall be madecondition of that tank, an evaluation shall be madeto determine its suitability for continued use.to determine its suitability for continued use.

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Factors to ConsiderFactors to Consider

Internal corrosion due to the product stored orInternal corrosion due to the product stored or water bottoms. water bottoms.

Water, 2 to 3 feet

Product

This is used to control productleakage through the bottom,

where the product is lighter than water and a bottom leak isdetected.

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External corrosion due to environmentalExternal corrosion due to environmentalexposure.exposure.

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Stress levels and allowable stress levels.Stress levels and allowable stress levels.

Properties of the stored product.Properties of the stored product.

Metal design temperature.Metal design temperature.

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Suitability For ServiceSuitability For ServiceExternal roof live load, wind, and seismicExternal roof live load, wind, and seismicloadings.loadings.

Tank foundation, soil, and settlement Tank foundation, soil, and settlementconditions.conditions.

Chemical analysis and mechanical propertiesChemical analysis and mechanical propertiesof the materials of construction.of the materials of construction.

Distortions of the existing tank.Distortions of the existing tank.Operating conditions such as filling/emptying Operating conditions such as filling/emptying rates and frequency.rates and frequency.

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Suitability for ServiceSuitability for Service

Fixed Roof

Roof Support Members

Rafters

Girders

Columns

Bases

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Suitability for ServiceSuitability for ServiceFloating Roofs

PontoonsCracks

PuncturesPlates

Corrosion

Pitting

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Change of ServiceChange of ServiceInternal PressureInternal Pressure

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Change of ServiceChange of ServiceExternal PressureExternal Pressure

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Change of ServiceChange of ServiceOperation at Elevated TemperatureOperation at Elevated Temperature

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Change of ServiceChange of ServiceOperation at a lower temperature than originalOperation at a lower temperature than original

designdesign

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Change of ServiceChange of ServiceNormal and Emergency Venting Normal and Emergency Venting

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Tank Shell Evaluation Tank Shell Evaluation

The evaluation should include: The evaluation should include:

Analysis for intended design conditions Analysis for intended design conditions

Shell plate thicknessShell plate thicknessMaterialMaterial

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The evaluation should include: The evaluation should include:

Anticipated loading conditions Anticipated loading conditions

Head pressureHead pressure

Wind loads Wind loads

SettlementSettlement Attachment loads Attachment loads

Internal & external pressureInternal & external pressure

Seismic loadsSeismic loads

Roof loadsRoof loads

Nozzle loadsNozzle loads

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If requirements cannot be satisfied:If requirements cannot be satisfied:Corroded areas repairedCorroded areas repaired

Allowable liquid level reduced Allowable liquid level reduced

Tank retired Tank retired

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Actual Thickness Determination Actual Thickness Determination

Thickness Averaging Thickness Averaging Step 1:Step 1: The Authorized Inspector shall The Authorized Inspector shall

determine the minimum thickness, tdetermine the minimum thickness, t 22

Step 2:Step 2: To calculate the mysterious To calculate the mysterious LL

a. Determine ta. Determine t22

(The least thickness, in(The least thickness, ininches, in an area of corrosion, exclusiveinches, in an area of corrosion, exclusiveof pits.)of pits.)

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b.b. Calculate L = 3.7 times the square root of Calculate L = 3.7 times the square root of the Diameter of the tank, times tthe Diameter of the tank, times t 22,,

OrOr

Note "L" is not to be more than 40"Note "L" is not to be more than 40"2

tD3.7L =

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LL = The maximum vertical length, in inches,= The maximum vertical length, in inches,over which hoop stresses are assumed toover which hoop stresses are assumed to"average out"average out around local discontinuities.around local discontinuities.

The actual vertical length of the corroded area The actual vertical length of the corroded areamay exceed "L".may exceed "L".

DD = Tank diameter, in feet.= Tank diameter, in feet.


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A tank 38 feet tall, 150 feet diameter, displays A tank 38 feet tall, 150 feet diameter, displaysa large area of corrosion. The corroded areaa large area of corrosion. The corroded areameasures approximately 23 inches wide andmeasures approximately 23 inches wide and21 inches in height. The inspector has21 inches in height. The inspector hasdetermined the least thickness, in the area of determined the least thickness, in the area of

corrosion to be 3/16 or .187 inches.corrosion to be 3/16 or .187 inches.Calculate the "L" length.Calculate the "L" length.

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L = 3.7L = 3.7 DtDt 22

L = 3.7L = 3.7 (150 X .187)(150 X .187)

L = 3.7L = 3.7 28.0528.05

L = 3.7 X 5.30L = 3.7 X 5.30

L = 19.61 inches or 19 5/8 inches approx.L = 19.61 inches or 19 5/8 inches approx.

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What do you do with the What do you do with themysterious "mysterious " LL" length?" length?

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4.3.2.1 c4.3.2.1 c Then, the Authorized Inspector shall Then, the Authorized Inspector shall

visually or otherwise decide which vertical plane(s) visually or otherwise decide which vertical plane(s)in the area is likely to be the most affected byin the area is likely to be the most affected bycorrosion. Profile measurements shall be takencorrosion. Profile measurements shall be takenalong each vertical plane for a distance, L. In thealong each vertical plane for a distance, L. In the

plane(s), determine the lowest average thickness, plane(s), determine the lowest average thickness,tt11, average over a length of L, using at least five, average over a length of L, using at least fiveequally spaced measurements over length L.equally spaced measurements over length L.

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Shell EvaluationShell Evaluation

Locate L to get minimumLocate L to get minimum

ttavg avg , which is t, which is t11

Minimum of 5 equally Minimum of 5 equally

spaced measurementsspaced measurementsttminmin = Minimum acceptable= Minimum acceptable

thickness, (in) for eachthickness, (in) for eachcourse, tcourse, tminmin shall not be lessshall not be lessthan 0.100 inchesthan 0.100 inches

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SE

HDGt

6.2min

=

( )SE

DG H t

16.2min

=

For locally thinned or any otherlocation of interest

For determining the minimumacceptable thickness for an entire

shell course

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Maximum Allowable StressMaximum Allowable Stress (PSI)(PSI)

Table 6 Table 6 --11

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Joint Efficiencies Joint Efficiencies

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Joint Efficiencies Joint Efficiencies

h ll l

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Pitting CorrosionPitting Corrosion

d i i

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Hydrostatic TestingHydrostatic Testing

H t = Height from the bottom of the shell course underconsideration to the hydrostatic test height when

evaluating an entire shell course; or

Height from the bottom of length L, (see 4.3.2.1) for themost severely thinned area in each shell course to thehydrostatic test height

Height from the lowest point within any other locationof interest to the hydrostatic test height

St = Maximum allowable hydrostatic test stress in psi, use thesmaller of 0.88Y or 0.472T for bottom and secondcourse; use the smaller of 0.9Y or 0.519T for all othercourses

16.2

min +=

D

Et S H t

t

D

Et S H t

t

6.2min=

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Minimum Thickness Calculation forMinimum Thickness Calculation for

Welded Tank Shell Welded Tank Shell

Sample problem for minimum thickness of aSample problem for minimum thickness of a welded tank shell. welded tank shell.

A 190 ft diameter tank has a pit that measures 5/16 A 190 ft diameter tank has a pit that measures 5/16inches deep in the first course, what is the mininches deep in the first course, what is the minthickness, if the fill is 42 ft and the specific gravitythickness, if the fill is 42 ft and the specific gravityis 0.6? (The pit is not in a weld seam or HAZ.)is 0.6? (The pit is not in a weld seam or HAZ.)

ttminmin == 2.6DHG2.6DHG

SESE

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Minimum Thickness Calculation forMinimum Thickness Calculation for

Welded Tank Shell Welded Tank Shell

ttminmin == 2.6DHG2.6DHGSESE

S =S = Maximum allowable stress in pounds perMaximum allowable stress in pounds persquare inch; use Table 4square inch; use Table 4 --11..

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Minimum Thickness Calculation for WeldedMinimum Thickness Calculation for Welded Tank Shell Tank Shell

Explanation of Sample Question (ConExplanation of Sample Question (Con t)t)ttminmin == 2.6DHG2.6DHG

SESEttminmin == 2.6 X 190(42)(.6)2.6 X 190(42)(.6)

23,600 X 123,600 X 1

ttminmin == 12,448.812,448.823,60023,600

tmin = .527 inches (13.4 mm)tmin = .527 inches (13.4 mm)

Ultrasonic Thickness of the ShellUltrasonic Thickness of the Shell

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Raw Shell Thickness Data

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Averaged ThicknessData over L c


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Consider corrosion rateConsider corrosion rate

Changes Inspection IntervalChanges Inspection Interval

May need to alter operations of the tank May need to alter operations of the tank

May need to consider mitigative measuresMay need to consider mitigative measures

DistortionsDistortions

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Shell distortions include:Shell distortions include:

OutOut --of of --roundnessroundness

Buckled areasBuckled areas

Flat spotsFlat spots

Peaking and banding at welded joints.Peaking and banding at welded joints.


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Shell distortions can be caused by many conditions such as:Shell distortions can be caused by many conditions such as:

Foundation settlement,Foundation settlement,

OverOver -- or underor under --pressuring,pressuring,

High wind,High wind,

Poor shell fabrication, orPoor shell fabrication, or

Repair techniques, andRepair techniques, and

So forth.So forth.


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Shell distortions shall be evaluated on anShell distortions shall be evaluated on anindividual basis to determine if specificindividual basis to determine if specificconditions are considered acceptable forconditions are considered acceptable forcontinuing tank service and/or the extent of continuing tank service and/or the extent of

corrective action.corrective action.

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Peaking and Banding Peaking and Banding

Result of:Result of: Improper plate fitImproper plate fit --upup

Too much heat input from welding from oneToo much heat input from welding from one

sideside

Improper root opening between platesImproper root opening between plates

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Peaking and Banding Peaking and Banding Possible Problems:Possible Problems:

Plate flattening or deformationPlate flattening or deformation

Increased residual stress levelsIncreased residual stress levels

Potential for fatigue failure if areaPotential for fatigue failure if area worksworks during product load/unloadduring product load/unloadconditionsconditions

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Sweep BoardSweep Board -- HorizontalHorizontal

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Shell PenetrationsShell Penetrations

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The condition and details of existing shell The condition and details of existing shell

penetrations (nozzles,penetrations (nozzles, manwaysmanways, cleanout, cleanoutopenings, etc.) shall be reviewed when assessing openings, etc.) shall be reviewed when assessing the integrity of an existing tank shell.the integrity of an existing tank shell.


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Details such as type and extent of:Details such as type and extent of:reinforcementreinforcement

weld spacing weld spacing thickness of components (reinforcing plate, nozzle neck, bolting thickness of components (reinforcing plate, nozzle neck, bolting flange,flange,and cover plate)and cover plate)

are important considerations and shall be reviewed for structuraare important considerations and shall be reviewed for structura lladequacy and compliance with the applicable standard.adequacy and compliance with the applicable standard.

Any noncompliance, or deterioration due to corrosion, must be Any noncompliance, or deterioration due to corrosion, must beassessed and repair procedures established where appropriate orassessed and repair procedures established where appropriate or thethetank rerated, as necessary.tank rerated, as necessary.

Tank Bottom Evaluation Tank Bottom Evaluation

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Tank Bottom Evaluation

Tank bottom inspection strategies shall provide

suitable data whichDetermine tank bottom integrity

Each aspect of corrosion phenomena andother potential leak or failure mechanismmust be examined

Tank Bottom Evaluation Tank Bottom Evaluation

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Periodic assessment of the tank bottom integrity

shall be performed in addition to the internal

inspections specified in 6.4

Leak detection

Monitoring systems

D o u b l e b o t t o m s L i n e r s u n d e r t a n k b o t t o m

L e a k d e t e c t i o n p i p e s

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Causes of Bottom FailureCauses of Bottom Failurea.a. Internal pitting and pitting rates in the anticipatedInternal pitting and pitting rates in the anticipated

service.service.b. Corrosion of weld joints .b. Corrosion of weld joints .

c.c. Weld joint cracking history. Weld joint cracking history.d. Stress placed on the bottom plates by roof supportd. Stress placed on the bottom plates by roof support

loads and shell settlement.loads and shell settlement.

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Causes of Bottom FailureCauses of Bottom Failuree.e. Underside corrosionUnderside corrosion

f.f. Inadequate drainage resulting in surface waterInadequate drainage resulting in surface waterflowing under the tank bottom.flowing under the tank bottom.

g. The lack of an annular plate ring when required.g. The lack of an annular plate ring when required.h. Uneven settlementh. Uneven settlement

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Causes of Bottom FailureCauses of Bottom Failure

i.i.

Roof support columns or other supports welded toRoof support columns or other supports welded tothe tank bottom.the tank bottom.

j.j. Rock or gravel foundation pads with inadequatelyRock or gravel foundation pads with inadequately

filledfilled --in surface voids.in surface voids.k. Nonhomogeneous fill under the tank bottom.k. Nonhomogeneous fill under the tank bottom.l.l. Inadequately supported sumps.Inadequately supported sumps.

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Sketch Plate Bottom LayoutSketch Plate Bottom Layout

Sketch Plate BottomSketch Plate Bottomusually lap weldedusually lap welded

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Annular Bottom Plate Ring Annular Bottom Plate Ring

Annular Bottom Plate Annular Bottom Plate Annular Bottom Plate Annular Bottom PlateRing Usually ButtRing Usually Butt Ring With a LapRing With a Lap

Welded Welded Welded Floor Welded Floor


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Cathodic Protection for Tank BottomsCathodic Protection for Tank Bottoms API RP 651 API RP 651

Internal Lining Protection of Tank BottomsInternal Lining Protection of Tank Bottoms

API RP 652 API RP 652

Bottom Leak DetectionBottom Leak Detection

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If tank bottom is to be replacedIf tank bottom is to be replaced

Consideration given to installing a leak Consideration given to installing a leak

detection systemdetection system

Minimum Thickness for Bottom PlatesMinimum Thickness for Bottom Plates

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One Acceptable Method:One Acceptable Method: (Deterministic Method)(Deterministic Method)

MRT = (Minimum of RTMRT = (Minimum of RT bcbc or RTor RT ipip ) ) OO rr(StP(StPrr + UP+ UP rr ) )MRT = minimum remaining thickness at the end of interval O r. This value must meet the

requirements of Table 6-1 and 4.4.7.4 and 4.4.8

O r = In-service interval of operation not to exceed that allowed in 6.4.2RT bc = minimum remaining thickness from bottom side corrosion after repairs

RT ip = minimum remaining thickness from internal corrosion after repairs

StP r = maximum rate of corrosion no repaired on the top side. StP r = 0 for coated areas of the

bottom. The expected life of the coating must equal or exceed Or to use StP r = 0.UP r = maximum rate of corrosion on the bottom side. To calculate the corrosion rate, use the

minimum remaining thickness after repairs. Assume a linear rate based on the age of thetanks. UP r= 0 for areas that have effective cathodic protection

Minimum Thickness for Bottom PlatesMinimum Thickness for Bottom Plates

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Probabilistic MethodProbabilistic Method

Used when sample scans are madeUsed when sample scans are made

Statistical analysis is performedStatistical analysis is performed

Extreme Value Analysis (EVA)Extreme Value Analysis (EVA)

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Minimum Thickness for Bottom PlatesMinimum Thickness for Bottom Platesin the Critical Zonein the Critical Zone

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in the Critical Zonein the Critical Zone

Perform a stress analysisPerform a stress analysis

original bottom plate thicknessoriginal bottom plate thickness

50% t50% tminmin of bottom shell courseof bottom shell course

Not less than 0.100 inches.Not less than 0.100 inches.

Bottom Plate RepairBottom Plate Repair

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Pit welding Pit welding

Overlay welding Overlay welding

Lap patching Lap patching Followed by inspection and testing Followed by inspection and testing

The repair of pits by non The repair of pits by non -- welded repairs welded repairscannot be used to increase RTcannot be used to increase RT ipip

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Bottom Plate ExtensionBottom Plate Extension

Not Less than0.1 Inch

3/8"Min.

Tank Shell

Tank Bottom(Inside)

Bottom Extension(Outside)

The thickness of theThe thickness of theprojection of the bottom plateprojection of the bottom platebeyond the shell as measuredbeyond the shell as measuredat the toe of the outsideat the toe of the outsidebottombottom --toto --to shell fillet weldto shell fillet weld

shall not be less than 0.1 inch.shall not be less than 0.1 inch.The projection of the bottomThe projection of the bottomplate beyond the outside toe of plate beyond the outside toe of the shellthe shell --toto --bottom weld shallbottom weld shall

be at least 3/8 inch.be at least 3/8 inch.

Magnetic Flux LeakageCoil Sensors

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Hall Effect Sensors

Technology adapted from Smart Pig Technology

Minimum Thickness for Annular Plate RingMinimum Thickness for Annular Plate Ring

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Due to strength requirements, the minimumDue to strength requirements, the minimumthickness of annular plate ring is usually greaterthickness of annular plate ring is usually greaterthan 0.100 in.than 0.100 in.

Unless a stress analysis is performed, the annularUnless a stress analysis is performed, the annularplate thickness shall be:plate thickness shall be:

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Tanks in service with a product specific gravity Tanks in service with a product specific gravity of of 1.0 or greater1.0 or greater, which require annular plates, which require annular platesfor other than seismic the thickness shall not befor other than seismic the thickness shall not beless than:less than:


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Tanks requiring annular plates for seismic Tanks requiring annular plates for seismicconsiderations, a seismic evaluation shallconsiderations, a seismic evaluation shall

be performed using the applicablebe performed using the applicablestandard.standard.

Tank Foundation Evaluation Tank Foundation Evaluation

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Causes of foundation deteriorationCauses of foundation deterioration

SettlementSettlementErosionErosion

Cracking Cracking

Calcining Calcining

Attack by alkalis and acids Attack by alkalis and acids


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Concrete pads, ringwalls and piers showing Concrete pads, ringwalls and piers showing

evidence of spalling, structural cracks, or generalevidence of spalling, structural cracks, or generaldeterioration shall be repaired to prevent waterdeterioration shall be repaired to prevent water

from entering the concrete structural andfrom entering the concrete structural and

corroding the reinforcement steel.corroding the reinforcement steel.


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Appendix B of API 653 provides Appendix B of API 653 provides

methodologies of tank bottommethodologies of tank bottomsettlement evaluationsettlement evaluation

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88

API 653 API 653Brittle FractureBrittle Fracture

Section 5Section 5

Brittle FractureBrittle Fracture

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Material ToughnessMaterial Toughness

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Defect ToleranceDefect Tolerance

Fracture InitiationFracture Initiation


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Propagation

Typically only a problem for gas pipelines

Can be a concern on aboveground storage

tanks

Propagating Brittle Fracture in a Gas Pipeline

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Propagated Ductile

F t i G

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Fracture in a GasPipeline

Basic Concepts in Fracture Control and ArrestFracture Toughness Testing

T i l CVN

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Typical CVNtesting rig

Calibrated hammer swingsthrough and breaks specimen.

Angle of swing on follow-through indicates amount of absorbed impact energy.

Low angle = high absorbed energy = high toughness and

vice-versa.

Basic Concepts in Fracture Control and ArrestBasic Concepts in Fracture Control and ArrestFracture Toughness TestingFracture Toughness Testing

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DropDrop -- Weight Tear Test (DWTT), thickness Weight Tear Test (DWTT), thicknessequal to pipe wall x 3 inches wide, 0.2equal to pipe wall x 3 inches wide, 0.2--inchinchnotch pressed, or machined chevron.notch pressed, or machined chevron.


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CVNSpecimen

DWTSpecimen


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API 5L specified orientation of impact test specimens

Coupon Size10mm by 10mm

2mm v-notch

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Ductile

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Ductile

Brittle

Typical profile of fractured CVNspecimens. Note deformation atedges of ductile specimen, lack of

deformation on brittle specimen.

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101

Full size CVNs

2/3-size CVNs -size CVNs

Basic Concepts in Fracture Control andBasic Concepts in Fracture Control and Arrest Arrest

Effect of Load Rate: Initiation &Effect of Load Rate: Initiation &

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Effect of Load Rate: Initiation &Effect of Load Rate: Initiation &PropagationPropagation

High load rate shiftsHigh load rate shiftstransition temperaturetransition temperaturedownward ~downward ~ 60 F60 F

Initiation is a staticInitiation is a staticprocess whileprocess whilepropagation is apropagation is adynamic processdynamic process

Basic Concepts in Fracture Control andBasic Concepts in Fracture Control and Arrest Arrest

Effect of Load Rate: Initiation &Effect of Load Rate: Initiation &

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Effect of Load Rate: Initiation &Effect of Load Rate: Initiation &PropagationPropagation

If TIf T opop< FITT, pipe< FITT, pipesusceptible to brittle (low susceptible to brittle (low stress) fracturestress) fracture

If FITT< TIf FITT< T opop< FPTT,< FPTT,initiation is ductile, butinitiation is ductile, butmay propagate as brittlemay propagate as brittlefracturefractureFracture arrest only Fracture arrest only assured by Tassured by Topop> FPTT> FPTT


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Mechanical DamageMechanical Damage

Compresses grain sizeCompresses grain sizeMaterial becomes brittleMaterial becomes brittle

Defect tolerance decreasesDefect tolerance decreases

Fracture initiationFracture initiation

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Typicalmechanical

damage

Typical mechanicaldamage

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Note creases in pipe wall(left); cracking, and crushed microstructure (below).

API 653 Brittle Fracture API 653 Brittle Fracture

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Designed to provide a procedure for theDesigned to provide a procedure for the

assessment of tanks for suitability forassessment of tanks for suitability forcontinued use or change of service withcontinued use or change of service withrespect to the risk of brittle fracture.respect to the risk of brittle fracture.

Does not supplement or replace theDoes not supplement or replace therequirements of Section 10 for the hydrorequirements of Section 10 for the hydro --testing of repaired, modified, ortesting of repaired, modified, orreconstructed tanks.reconstructed tanks.

API 653 Brittle Fracture API 653 Brittle Fracture

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The procedure applies to both welded and The procedure applies to both welded andriveted tanks; however, the procedure isriveted tanks; however, the procedure isbased primarily on experience and databased primarily on experience and data

obtained from welded tanks.obtained from welded tanks.

API 653, Brittle Fracture API 653, Brittle Fracture

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Failure has occurred shortly after:Failure has occurred shortly after:

Erection during hydrostatic testingErection during hydrostatic testingor on the first filling in cold weatheror on the first filling in cold weather

A change to a colder serviceA change to a colder service

A repair or alterationA repair or alteration


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History indicates that once a tank hasHistory indicates that once a tank has

shown the ability to withstand theshown the ability to withstand thecombined effects of maximum liquidcombined effects of maximum liquidlevel (highest stresses as duringlevel (highest stresses as duringhydrohydro --test) and lowest operatingtest) and lowest operatingtemperature without failing, the risk of temperature without failing, the risk of

failure due to brittle fracture withfailure due to brittle fracture withcontinued service is minimal.continued service is minimal.


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AnyAny changes in tank use must bechanges in tank use must beevaluated to determine if it increasesevaluated to determine if it increasesthe risk of failure due to brittle fracture.the risk of failure due to brittle fracture.

If the change is to a more severeIf the change is to a more severeservice, consider the need for aservice, consider the need for ahydrostatic test to show fitness for thehydrostatic test to show fitness for themore severe service.more severe service.


The following aspects should be considered:The following aspects should be considered:

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The following aspects should be considered: The following aspects should be considered:

a. The possibility of repairs/alterationsa. The possibility of repairs/alterationshaving occurred since the originalhaving occurred since the originalhydrostatic test and that these repairs mayhydrostatic test and that these repairs may

not meet requirements of this standard.not meet requirements of this standard.bb .. General deterioration of theGeneral deterioration of the tanktank sincesince

original hydrostatic test occurred.original hydrostatic test occurred.

Assessment Procedure Assessment Procedure

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Tanks may also be shown to meet the Tanks may also be shown to meet the

toughness requirements of APItoughness requirements of APIStandard 650 (seventh edition orStandard 650 (seventh edition or

later) by impact testing couponlater) by impact testing couponsamples from a representativesamples from a representative

number of shell plates.number of shell plates.

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If theIf the tanktank shell design thickness is

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No reported brittle fracture tank failuresNo reported brittle fracture tank failures

have occurred at shell metal temperatureshave occurred at shell metal temperatures 6060 F.F.

Heating the contents can add assuranceHeating the contents can add assuranceagainst brittle fracture.against brittle fracture.


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I d i d l bI d t i d l b t t t

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Industry experience and laboratory testsIndustry experience and laboratory tests

have shown that a membrane stress inhave shown that a membrane stress intank shell plates of at least 7tank shell plates of at least 7 ksiksi isisrequired to cause failure due to brittlerequired to cause failure due to brittlefracture.fracture.


k d f l l dT k d f l li d

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Tanks constructed from steels listed Tanks constructed from steels listed

in Figure 2in Figure 2 --1 of API Standard 650 can1 of API Standard 650 canbe used in accordance with theirbe used in accordance with theirexemption curves, provided that anexemption curves, provided that anevaluation for suitability of service inevaluation for suitability of service inconformance with Section 4 of thisconformance with Section 4 of thisstandard has been performed.standard has been performed.


T k f b i d f l fT k f b i d f l f

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Tanks fabricated from steels of Tanks fabricated from steels of

unknown toughness thicker than inchunknown toughness thicker than inchand operating at a shell metaland operating at a shell metaltemperature below 60temperature below 60 F can be usedF can be usedif theif the tanktank meets the requirements of meets the requirements of FigureFigure 55--2.2.


Th i i l i l hi k fTh i i l i l thi k f

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The original nominal thickness for The original nominal thickness for

thickestthickest tanktank shell plate shall be usedshell plate shall be usedfor the assessment.for the assessment.

For unheated tanks, the shell metalFor unheated tanks, the shell metaltemperature shall be the design metaltemperature shall be the design metaltemperaturetemperature asas defined in 2.2.9.3 of defined in 2.2.9.3 of API 650API 650


Th i k f f il d t b ittlTh i k f f il d t b ittl

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The risk of failure due to brittle The risk of failure due to brittle

fracture is minimal once a tank hasfracture is minimal once a tank hasdemonstrated that it can operate at ademonstrated that it can operate at aspecified maximum liquid level at thespecified maximum liquid level at thelowest expected temperature withoutlowest expected temperature withoutfailing.failing.


AAn l ti b f de al ation can be performed tt

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AnAn evaluation can be performedevaluation can be performed toto

establish a safe operating envelopeestablish a safe operating envelopefor afor a tanktank based on the past operatingbased on the past operatinghistory. This evaluation shall behistory. This evaluation shall bebased on the most severebased on the most severecombination of temperature and liquidcombination of temperature and liquid

level experienced bylevel experienced by the tank duringthe tank duringits life.its life.


The evaluation mayshowthatthe tankThe evaluation mayshowthatthe tank

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The evaluation may show that the tank The evaluation may show that the tank

needs to be rerated or operated differently;needs to be rerated or operated differently;several options exist:several options exist:a.a. Restrict the Liquid level.Restrict the Liquid level.

b. Restrict the minimum metal temperature.b. Restrict the minimum metal temperature.

c. Change the service to a stored product withc. Change the service to a stored product with

a lower specific gravity.a lower specific gravity.d. Combinationsd. Combinations of a, b, and c, above.of a, b, and c, above.


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The owner/operator can also make a The owner/operator can also make amore rigorous analysis to determine themore rigorous analysis to determine therisk of failure due to brittle fracture byrisk of failure due to brittle fracture by

performing a fracture mechanicsperforming a fracture mechanicsanalysis based upon establishedanalysis based upon establishedprinciples and practices.principles and practices.


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AnAn assessment shall be madeassessment shall be madeto determine if the change into determine if the change in

service places theservice places the tanktank atatgreater risk of failure due togreater risk of failure due to

brittle fracture.brittle fracture.

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131

API 653 API 653InspectionInspection

Section 6Section 6

Section 6Section 6 -- InspectionInspection

F b id d

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Nature of stored productNature of stored productResults of visual maintenance checksResults of visual maintenance checks

Corrosion allowances and corrosion ratesCorrosion allowances and corrosion rates

Corrosion prevention systemsCorrosion prevention systems

Factors to be considered


Factors to be consideredFactors to be considered

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Conditions at previous inspections

Methods & materials of construction Location of tanks

Risk of pollution


Factors to be consideredFactors to be considered

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Leak detection systems

Change in operation mode

Jurisdictional requirements

Changes in service Existence of RPB

Inspections from Outside the Tank Inspections from Outside the Tank

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Routine InRoutine In --Service InspectionsService InspectionsExternal InspectionExternal Inspection

Ultrasonic Thickness InspectionUltrasonic Thickness Inspection

Cathodic Protection SurveysCathodic Protection Surveys


Routine InRoutine In --Service InspectionsService Inspections

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pp

External condition of the tank External condition of the tank Close visual inspectionClose visual inspection

From the groundFrom the ground



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p

Who can perform this inspection? Who can perform this inspection?

Owner/Operator



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How Often?How Often?

Consistent with the conditions at the

particular site.

Not to exceed 1 Month



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What do you look for? What do you look for?

Shell distortions

Settlement

Corrosion



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What do you look for? What do you look for?

Foundation settlement Coating deterioration

Insulation deterioration

Appurtenances



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What do you do with this? What do you do with this?

Document for follow-up action by anauthorized inspector


External InspectionExternal Inspection

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Who can perform this inspection? Who can perform this inspection?

Authorized Inspector



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Must be conducted at leastMust be conducted at least

5 Years5 YearsQuarter corrosion rate life of the shellQuarter corrosion rate life of the shell



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Insulated tanks need to insulationInsulated tanks need to insulation

removed only to the extent necessary toremoved only to the extent necessary todetermine the condition of the exteriordetermine the condition of the exterior

wall of the tank or roof. wall of the tank or roof.


Ultrasonic InspectionUltrasonic Inspection

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Means of determining the rate of Means of determining the rate of

uniform general corrosionuniform general corrosionProvide an indication of the shellProvide an indication of the shell

integrity integrity



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The extent shall be determined by the The extent shall be determined by the

owner/operatorowner/operator



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IntervalInterval

5 Years when corrosion rate is not known5 Years when corrosion rate is not known

The smaller of The smaller of

RCA/2NRCA/2N15 Years15 Years



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Internal inspection of the tank shell canInternal inspection of the tank shell can

substitute for a program of external UTsubstitute for a program of external UTmeasurements.measurements.



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Periodic Surveys of the cathodicPeriodic Surveys of the cathodic

protection system shall be conducted inprotection system shall be conducted inaccordance with API RP 651.accordance with API RP 651.



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The owner/operator shall assure The owner/operator shall assure

competency of the personnel performing competency of the personnel performing surveys.surveys.

Internal InspectionInternal Inspection

Internal inspection is primarily required to:Internal inspection is primarily required to:

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p p y qp p y q Ensure that the bottom is not severely

corroded

Gather the data necessary for the minimumbottom and shell thickness assessments

Identify and evaluate any tank bottomsettlement


The Authorized Inspector Must: The Authorized Inspector Must:

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p

Conduct a visual inspection

Assure the quality and completeness of NDE


Inspection Intervals:Inspection Intervals:

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Determined by corrosion rates

Not to exceed 20 years If corrosion rates not available, 10 years


Minimum PlateMinimum PlateThickness at NextThickness at Next Tank Bottom/Foundation DesignTank Bottom/Foundation Design

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Thickness at Next Thickness at NextInspectionInspection

Tank Bottom/Foundation Design Tank Bottom/Foundation Design

0.1000.100 Tank bottom/foundation design with no means for Tank bottom/foundation design with no means fordetection and containment of a bottom leak detection and containment of a bottom leak

0.0500.050 Tank bottom/foundation design with means to Tank bottom/foundation design with means toprovide detection and containment of a bottomprovide detection and containment of a bottomleak.leak.

0.0500.050 Applied tank bottom reinforcing lining, >0.05 inch Applied tank bottom reinforcing lining, >0.05 inchthick, in accordance with API RP 652.thick, in accordance with API RP 652.


Risk Based Inspection (RBI):Risk Based Inspection (RBI):

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Alternative to Standard Inspection Programs

Establish acceptable minimum bottom thickness Can increase or decrease 20 year criteria

Inspection ChecklistInspection Checklist

API Appendix CAPI Appendix C

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Non-mandatory Sample

Illustratescomponents that

should beconsidered

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157

API 653 API 653 Tank Repair and Alteration Tank Repair and Alteration

Section 9Section 9

GeneralGeneralNew RequirementsNew Requirements

All repair work must be authorized by the authorizedinspector or an engineer

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Authorization for alterations to storage tanks that comply with API Std 650 may not be given without priorconsultation with an Engineer

The authorized inspector will designate inspection hold

points and minimum documentation to be submitted uponjob completion. The authorized inspector may give prior generalauthorization for limited or routine repairs as long as therepairs will not require hydrostatic testing or do not requirean engineering evaluation.

GeneralGeneral

New RequirementsNew Requirements

All proposed design, work execution, materials, welding

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All proposed design, work execution, materials, welding procedures, examination, and testing methods must beapproved by the authorized inspector or by an engineer.

The authorized inspector or an engineer shall approveall specified repair and alteration work at the designatedhold points and after repairs and alterations have beencompleted in accordance with the requirements of this

standard.

GeneralGeneral

New RequirementsNew Requirements

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qq

Appendix F summarizes the requirements by Appendix F summarizes the requirements by method of examination and providesmethod of examination and providesacceptance standards.acceptance standards.

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Weld Joint Design. Weld Joint Design.

Shell replacement plate shall be butt welded toexisting shell plate material, except for lapped shell

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repairs.Require complete penetrationRequire complete penetrationRequire complete fusionRequire complete fusion

Weld joints shall be per API Std 650. Lap weldedjoints may be repaired according to the original

standard.

Shell Plate RepairsShell Plate Repairs

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9

Weld Joint Design. Weld Joint Design.

To reduce potential for To reduce potential for

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distortion of an existing tank, fitdistortion of an existing tank, fit--up, heat input, and welding up, heat input, and welding sequence must be considered.sequence must be considered.

LapLap -- Welded Patch Plates Welded Patch Plates

Lapped patch shell repairs are an acceptable form of Lapped patch shell repairs are an acceptable form of repair under the conditions outlined in 9.3.2 to 9.3.4,repair under the conditions outlined in 9.3.2 to 9.3.4,

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only when specified by the owner.only when specified by the owner.


May be used for the closure of holes cause by May be used for the closure of holes cause by removal of existing shell openings or theremoval of existing shell openings or the

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removal of severely corroded areas.removal of severely corroded areas.May be used to reinforce areas severely May be used to reinforce areas severely

deteriorated shell plates.deteriorated shell plates.May be used to repair small leaksMay be used to repair small leaks


Shell Plate thickness

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ShapeShapeRounded, circular, oblong, square or rectangularRounded, circular, oblong, square or rectangular

All corners shall be rounded except those that All corners shall be rounded except those thatintersect the shellintersect the shell--toto--bottom. Min radius is 2 in.bottom. Min radius is 2 in.RepadRepad details from API Std 650 are also acceptabledetails from API Std 650 are also acceptable


May cross an existing seam weldMay cross an existing seam weldMust be ground flushMust be ground flush

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Patch must extend at least 6 in past the weld.Patch must extend at least 6 in past the weld.Figure 9Figure 9--1 used as the basis for placement1 used as the basis for placement


May intersect theMay intersect theT T

Tank Shell

W

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ShellShell-- To To --Bottom weldBottom weldprovided details of provided details of Figure 9Figure 9--2 are met.2 are met.

Repair Plate

Trim repair plate to clear Shell-to-bottomweld

W3/16

3/16

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UT The existing shell plateUT The existing shell plate

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Shall not be lapped onto lapShall not be lapped onto lap -- welded shell welded shellseams, riveted shell seams, other lapseams, riveted shell seams, other lap-- welded welded

repair plates, distorted areas, or unrepairedrepair plates, distorted areas, or unrepairedcracks or defectscracks or defects

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Repair of Defective WeldsRepair of Defective Welds

Cracks, lack of fusion, and rejectable slag or porosity Cracks, lack of fusion, and rejectable slag or porosity shall be removed by completely gouging and/orshall be removed by completely gouging and/orgrinding and the resulting cavity properly prepared for

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grinding and the resulting cavity properly prepared for welding. welding.Excessive weld reinforcementExcessive weld reinforcement

UndercutUndercutCorroded weld jointsCorroded weld joints

Arc Strikes Arc Strikes

Repair of Shell PenetrationsRepair of Shell Penetrations

In Compliance with API Std 650In Compliance with API Std 650

ff

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Reinforcing plates may be addedReinforcing plates may be addedMeet dimension requirements of API Std 650Meet dimension requirements of API Std 650

Figure 9Figure 9--3A and 93A and 9--3B for acceptable details3B for acceptable details


New shell penetrationsNew shell penetrations

R i f API S d 650R i f API S d 650

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Requirements of API Std 650Requirements of API Std 650

Penetrations larger than 2 in NPS shall installedPenetrations larger than 2 in NPS shall installed

with the use of an insert plate if with the use of an insert plate if Shell plate thickness >Shell plate thickness > inin

AND AND

Shell plate material does not meet current DMTShell plate material does not meet current DMT

Shell w/ insert plate

Modified reinforcement plate

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Modified reinforcement plate


New Shell Penetrations Insert RequirementsNew Shell Penetrations Insert Requirements

Mi Di t f i t l t 2 di t fMi Di t f i t l t 2 di t f

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Min. Diameter of insert plate = 2 x diameter of Min. Diameter of insert plate = 2 x diameter of the penetration + 12 inchesthe penetration + 12 inches

When reinforcing plates are used, the min When reinforcing plates are used, the mindiameter of the insert plate shall equal thediameter of the insert plate shall equal thediameter of the reinforcing plate + 12 inchesdiameter of the reinforcing plate + 12 inches


New Shell Penetrations Insert RequirementsNew Shell Penetrations Insert Requirements

If i t g l i f t l t d ig i dIf i t g l i f t l t d ig i d

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If an integral reinforcement plate design is used,If an integral reinforcement plate design is used,the thickness at its periphery and for a distance of the thickness at its periphery and for a distance of 2t shall be the thickness of the tank shell, 4:1 taper2t shall be the thickness of the tank shell, 4:1 taper

Spacing of welds shall conform to Figure 9Spacing of welds shall conform to Figure 9--11

The insert plate shall be butt The insert plate shall be butt -- welded welded

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Alteration of Shell Penetrations Alteration of Shell Penetrations

Existing shell penetrations may be modified if Existing shell penetrations may be modified if

th lt d d t il l ith thth lt d d t il l ith th

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the altered details comply with thethe altered details comply with therequirements of API Std 650requirements of API Std 650

When install a double bottom, it may become When install a double bottom, it may becomenecessary to alter the existing shellnecessary to alter the existing shell

penetrationspenetrations


The existing reinforcing The existing reinforcing plate may be trimmed toplate may be trimmed toincrease the spacing increase the spacing b h ldb t th ld

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between the weldsbetween the weldsprovided that theprovided that the

modified detail compliesmodified detail complies with API Std 650. with API Std 650.


The existing reinforcing plate may be removed The existing reinforcing plate may be removed

and a new reinforcing plate installedand a new reinforcing plate installed

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and a new reinforcing plate installedand a new reinforcing plate installedPart of stress relieved assembly Part of stress relieved assembly

Care taken not to damage existing shellCare taken not to damage existing shell


The existing penetration may be moved by The existing penetration may be moved by

cutting the section of the shell containing thecutting the section of the shell containing the

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cutting the section of the shell containing thecutting the section of the shell containing thefitting and reinforcing plate, and raising thefitting and reinforcing plate, and raising theentire assembly to the correct elevation.entire assembly to the correct elevation.

Repair of Tank BottomsRepair of Tank Bottoms

Patch PlatesPatch PlatesMinimum dimension is 12 inchesMinimum dimension is 12 inches

May be reduced to 6 inches if:May be reduced to 6 inches if:

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May be reduced to 6 inches if:May be reduced to 6 inches if:it does not overlap a bottom seamit does not overlap a bottom seamnot place fully or partially over an existing patch platenot place fully or partially over an existing patch plateExtends over corroded area by 2 inExtends over corroded area by 2 in

Repair of Tank BottomsRepair of Tank Bottoms

Patch PlatesPatch PlatesShall not be placed over:Shall not be placed over:

areas of global dishingareas of global dishing

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areas of global dishing areas of global dishing local dishing local dishing distorted areas greater than permitted by Appendix Bdistorted areas greater than permitted by Appendix B

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9

Repairs within the Critical ZoneRepairs within the Critical Zone

Patch Plates are permitted provided thePatch Plates are permitted provided thefollowing additional requirements are metfollowing additional requirements are met

Maximum thickness isMaximum thickness is inin

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Maximum thickness isMaximum thickness is inin Toughness requirements of API Std 650 Section Toughness requirements of API Std 650 Section2.2.9 are met2.2.9 are met

The plate is tombstone shaped The plate is tombstone shaped



Perimeter welds shall be twoPerimeter welds shall be two--pass minpass minE i d di 12 1 7 2 d 12 1 7 3E i d di t 12 1 7 2 d 12 1 7 3

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Perimeter welds shall be twoPerimeter welds shall be two pass minpass minExamined according to 12.1.7.2 and 12.1.7.3Examined according to 12.1.7.2 and 12.1.7.3Installation of a weldInstallation of a weld--on patch plate by button patch plate by butt -- welding welding

to an adjacent existing patch plate is not permittedto an adjacent existing patch plate is not permitted



WeldWeld--on patch plates over existing patches are noton patch plates over existing patches are notallowed in the critical zoneallowed in the critical zone

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Weld Weld on patch plates over existing patches are noton patch plates over existing patches are notallowed in the critical zoneallowed in the critical zone The bottom plate under the perimeter patch plate The bottom plate under the perimeter patch plate

shall meet the thickness requirements of 4.4shall meet the thickness requirements of 4.4


No welding or weld overlays are permittedNo welding or weld overlays are permitted within the critical zone except for widely within the critical zone except for widely

scattered pitsscattered pits.

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scattered pits. Weld Weld--on patch is not permitted if the bottomon patch is not permitted if the bottomplate thickness at the toe of the shellplate thickness at the toe of the shell --toto--bottombottom

weld will be less than the minimum thickness weld will be less than the minimum thicknessrequired at then next internal inspectionrequired at then next internal inspection


Weld Weld--on patch is not permitted for serviceon patch is not permitted for servicetemperatures > 200temperatures > 200 F for carbon steel or 100F for carbon steel or 100 FF

for stainless steelfor stainless steel

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for stainless steelfor stainless steelIf extensive repairs are required, then theIf extensive repairs are required, then the

bottom plate shall be removed and replace withbottom plate shall be removed and replace withnew new


The use of weld The use of weld --on patch plates not meeting on patch plates not meeting these requirements if the repair method hasthese requirements if the repair method has

been reviewed and approved by an engineer.been reviewed and approved by an engineer.

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been reviewed and approved by an engineer.been reviewed and approved by an engineer.

Replacement of Entire Tank BottomReplacement of Entire Tank Bottom

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The shell shall be slotted with a uniform cut The shell shall be slotted with a uniform cutmade parallel to the tank bottom.made parallel to the tank bottom.

The new bottom plate shall be extended outside The new bottom plate shall be extended outside

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ppthe shell as required by API Std 650 and all rulesthe shell as required by API Std 650 and all rules

for weld spacing shall be followedfor weld spacing shall be followed


Existing shell penetrations shall be raised if theExisting shell penetrations shall be raised if theelevation if the elevation of the new bottom cutselevation if the elevation of the new bottom cuts

through the reinforcing plate or if the weldthrough the reinforcing plate or if the weldi t gi i API Std 650 tspace req irements gi en in API Std 650 are not

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g g pg g pspace requirements given in API Std 650 are notspace requirements given in API Std 650 are notmet.met.


New rules for reduced weld spacing on shellNew rules for reduced weld spacing on shellnozzles for some tanks.nozzles for some tanks.

SMYSSMYS 50,000 PSI50,000 PSIh b h h ll4 i h i b h h ll b ld db ld d

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4 inches min between the shell4 inches min between the shell--toto--bottom weld andbottom weld andnearest penetration attachment weldnearest penetration attachment weldFor self reinforced penetrations greater of 3 inchesFor self reinforced penetrations greater of 3 inchesor 2.5tor 2.5t


New rules for reduced weld spacing on shellNew rules for reduced weld spacing on shellnozzles for some tanks.nozzles for some tanks.

ShellShell--toto--bottom weld is welded with low bottom weld is welded with low --hydrogenhydrogenelectrodeselectrodes

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electrodeselectrodes The toes of the welds are to be blend The toes of the welds are to be blend --ground.ground.MT before and after hydroMT before and after hydro


New bearing plates for floating roof supportsNew bearing plates for floating roof supportslegs and for the cone roof columnslegs and for the cone roof columns

Installation of the new bottom shall meet theInstallation of the new bottom shall meet thei f API S d 650i f API S d 650

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requirements of API Std 650requirements of API Std 650

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Repair Fixed RoofsRepair Fixed Roofs

Repair of Fixed RoofsRepair of Fixed RoofsSupported Cone RoofsSupported Cone Roofs

Self Self --Supporting RoofsSupporting Roofs

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Floating RoofsFloating Roofs

Repair of Floating RoofsRepair of Floating RoofsExternal Floating RoofsExternal Floating Roofs any method is acceptableany method is acceptable

Internal Floating RoofsInternal Floating Roofs in accordance with original drawings orin accordance with original drawings or

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in accordance with original drawings orin accordance with original drawings orCompliance with Appendix H of 650Compliance with Appendix H of 650

Repair of Leaking in Pontoons (Steel)Repair of Leaking in Pontoons (Steel)Rewelding orRewelding or

Patch PlatesPatch Plates

Seal RepairsSeal Repairs

Section 9.13 Repair orSection 9.13 Repair orReplacement of Floating Replacement of Floating

Roof Perimeter SealsRoof Perimeter Seals

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Hot TapsHot Taps

Requirements for Hot TapsRequirements for Hot TapsRequirements for tanks with known and unknown toughnessRequirements for tanks with known and unknown toughness

Unknown Toughness limited to 4 N.P.S.Unknown Toughness limited to 4 N.P.S.Known Toughness limited to 18 N.P.S.Known Toughness limited to 18 N.P.S.

P d t t l t 3 ft b th h t t i t ll tiP d t t l t 3 ft b th h t t i t ll ti

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Product at least 3 ft above the hot tap installationProduct at least 3 ft above the hot tap installationLow Low --hydrogen electrodeshydrogen electrodes

Thickness limitations based on nozzle size Thickness limitations based on nozzle sizeUT checks requiredUT checks required

Not permitted in vapor spaceNot permitted in vapor space API Publication 2201 API Publication 2201

How would you repair this?

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Tank Bottom Corrosion Tank Bottom Corrosion

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Hot Asphalt Tank Hot Asphalt Tank

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Tank BottomInspection Report

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Over Pressure Event

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Over Pressure Event

Area of top shellcourse damage.

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Areas of bottom plate lifting.These locations were directly

below the areas in the cone roof where the over-pressurizationhad damaged the roof plates.

Over Pressure Event

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Deformed Roof Plates.

Columns are not plumb.

P

L

U

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M

B

L

I

NE.

Shell Failure.

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Twisted Roof Structure.

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