SULFURIC ACID TANK INSPECTION INSPECTION By By By By Jeff Kitchen Jeff Kitchen Tank Engineering And Management Consultants, Inc.
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SULFURIC ACID TANK INSPECTIONINSPECTION
ByByByByJeff KitchenJeff Kitchen
Tank Engineering And Management Consultants, Inc.
Introduction
Jeff W. KitchenJeff W. KitchenVice President of TEAM ConsultantsVice President of TEAM ConsultantsVice President of TEAM ConsultantsVice President of TEAM ConsultantsNACE Certified Corrosion TechnologistNACE Certified Corrosion TechnologistAPIAPI 653 C tifi d T k I t653 C tifi d T k I tAPIAPI--653 Certified Tank Inspector653 Certified Tank InspectorAPIAPI--570 Certified Piping Inspector570 Certified Piping Inspector
Tank Engineering And Management Consultants, Inc.
Introduction
TEAM Consultants is currently under the TEAM Consultants is currently under the same ownership as Pennsame ownership as Penn--Pro Engineering.Pro Engineering.pp g gg gTEAM has been in business since 1983TEAM has been in business since 1983Originally founded by James EOriginally founded by James E PandolphPandolphOriginally founded by James E. Originally founded by James E. PandolphPandolph, , P.E..P.E..
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Corrosion in Sulfuric Acid Tanks
Corrosion = The deterioration of a Corrosion = The deterioration of a substance or it’s properties because of a substance or it’s properties because of a
i i h i ii i h i ireaction with it’s environment.reaction with it’s environment.Anytime you store liquids in a metal Anytime you store liquids in a metal
i h h i di fi h h i di fcontainer you have the ingredients for container you have the ingredients for corrosion.corrosion.
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Corrosion in Sulfuric Acid Tanks
Sulfuric acid ( HSulfuric acid ( H22SOSO44 ), in carbon steel ), in carbon steel tanks, reacts with iron in the shell to form a tanks, reacts with iron in the shell to form a ,,ferrous sulfate product and hydrogen ferrous sulfate product and hydrogen according to the reaction:according to the reaction:ggFe (iron) + HFe (iron) + H22SOSO44 (sulfuric acid) (sulfuric acid) --> FeSO> FeSO44(ferrous sulfate) + H(ferrous sulfate) + H22 (hydrogen)(hydrogen)(ferrous sulfate) H(ferrous sulfate) H22 (hydrogen)(hydrogen)
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Corrosion in Sulfuric Acid Tanks
TheThe FeSOFeSO44 formsforms aa protectiveprotective layerlayer betweenbetweenthethe acidacid andand tanktank wetwet surfacessurfaces..ManyMany conditionsconditions deterioratedeteriorate thisthis protectiveprotectivefilmfilm –– suchsuch asas flow,flow, liquidliquid turbulence,turbulence,dil idil i hh idid i hi h ddi i lddi i l hi hhi hdilutingdiluting thethe acidacid withwith additionaladditional water,water, highhightemperature,temperature, oror agitationagitation..Wi hWi h ii filfil hh ll ii bjbjWithoutWithout protectiveprotective film,film, thethe steelsteel isis subjectsubjecttoto acceleratedaccelerated andand localizedlocalized corrosioncorrosion..
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Corrosion metal loss in acid storage tanks.Corrosion metal loss in acid storage tanks.gg
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Tank Construction StandardsVerticalVertical TanksTanksVerticalVertical TanksTanks
APIAPI 650650 -- TanksTanks areare usuallyusually ventedvented..HoweverHowever AppendixAppendix FF allowsallows smallsmallHowever,However, AppendixAppendix FF allowsallows smallsmallinternalinternal pressurespressures upup toto 22..55 psigpsig..APIAPI 620620 AppliesApplies toto designdesign pressurespressuresAPIAPI 620620 -- AppliesApplies toto designdesign pressurespressureslessless thanthan 1515 psigpsig..EqualEqual oror moremore thanthan 1515 psigpsig containerscontainers useuseEqualEqual oror moremore thanthan 1515 psigpsig containerscontainers useuseASMEASME SectionSection VIIIVIII –– PressurePressure VesselVesselCodeCode
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CodeCode..
Tank Construction StandardsAPIAPI 650650 asas de elopedde eloped forfor oiloil storagestorageAPIAPI 650650 waswas developeddeveloped forfor oiloil storagestorage(specific(specific gravitygravity <<11..00,, typicallytypically 00..7575 -- 00..9595))..TheThe specificspecific gravitygravity ofof 9393%% andand 9898%%TheThe specificspecific gravitygravity ofof 9393%% andand 9898%%sulfuricsulfuric acidsacids areare 11..83548354 andand 11..84378437respectivelyrespectively.. SulfuricSulfuric acidacid isis aboutabout doubledoublep yp ythethe weightweight ofof thethe lighterlighter oilsoils..AA sizablesizable corrosioncorrosion allowanceallowance isis typicallytypicallyyp yyp yaddedadded forfor sulfuricsulfuric acidacid serviceservice..
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Tank Construction StandardsHori ontalHori ontal TanksTanksHorizontalHorizontal TanksTanks
SectionSection VIIIVIII ofof ASMEASME BoilerBoiler && PressurePressureVesselVessel CodeCodeVesselVessel CodeCodeULUL--142142 isis NOTNOT suitablesuitable forfor sulfuricsulfuric acidacid..ItIt onlyonly appliesapplies toto nonnon corrosivecorrosive materialsmaterialsItIt onlyonly appliesapplies toto nonnon--corrosivecorrosive materialsmaterialswithwith aa specificspecific gravitygravity ofof 11..00 oror lessless..
Tank Engineering And Management Consultants, Inc.
Tank Inspection StandardsVerticalVertical TanksTanksVerticalVertical TanksTanks
APIAPI StandardStandard 653653 (Tank(Tank Inspection,Inspection,RepairRepair AlterationAlteration andand Reconstruction)Reconstruction)Repair,Repair, Alteration,Alteration, andand Reconstruction)Reconstruction)CoversCovers carboncarbon andand lowlow alloyalloy steelsteel tankstanksbuiltbuilt toto APIAPI StandardStandard 650650 andand itsitsbuiltbuilt toto APIAPI StandardStandard 650650 andand itsitspredecessorpredecessor 1212CC
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Tank Inspection StandardsHori ontalHori ontal TanksTanksHorizontalHorizontal TanksTanks
APIAPI StandardStandard 510510 (Pressure(Pressure VesselVesselInspectionInspection Code)Code)InspectionInspection Code)Code)IntendedIntended forfor pressurepressure vessels,vessels, butbut hashas thethebestbest criteriacriteria forfor formedformed headsheads thickthickbestbest criteriacriteria forfor formedformed heads,heads, thickthickplates,plates, supportsupport saddles,saddles, etcetc..
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Tank Inspection MethodsUltrasonic Thickness Meas rementsUltrasonic Thickness Meas rementsUltrasonic Thickness Measurements Ultrasonic Thickness Measurements (UTM’s)(UTM’s)
Pay careful attention to location andPay careful attention to location andPay careful attention to location and Pay careful attention to location and direction of testing.direction of testing.Take more UTM’s around typical highTake more UTM’s around typical highTake more UTM’s around typical high Take more UTM’s around typical high product level AND sludge line near tank product level AND sludge line near tank bottombottombottom.bottom.
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Example:Example:
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Tank Inspection MethodsUltrasonic Thickness Meas rementsUltrasonic Thickness Meas rementsUltrasonic Thickness Measurements Ultrasonic Thickness Measurements (UTM’s)(UTM’s)
Pay careful attention around nozzles andPay careful attention around nozzles andPay careful attention around nozzles and Pay careful attention around nozzles and vents, and directly on piping and flanges.vents, and directly on piping and flanges.It is important to combine visualIt is important to combine visualIt is important to combine visual It is important to combine visual inspection with UTM locations.inspection with UTM locations.
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Example:Example:
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Example:Example:
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Tank Inspection MethodsFloor Scanning in Vertical TanksFloor Scanning in Vertical TanksFloor Scanning in Vertical TanksFloor Scanning in Vertical Tanks
Magnetic Flux Leakage (MFL) only Magnetic Flux Leakage (MFL) only works up to ½” plate thicknessworks up to ½” plate thicknessworks up to ½” plate thickness.works up to ½” plate thickness.SLOFEC (Super Low Frequency Eddy SLOFEC (Super Low Frequency Eddy Current) will work on thicker materialsCurrent) will work on thicker materialsCurrent) will work on thicker materials.Current) will work on thicker materials.Spot UTM’s may be a suitable and Spot UTM’s may be a suitable and cheaper alternativecheaper alternativecheaper alternative.cheaper alternative.
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Tank Inspection MethodsLocation of Cracks In and Near WeldsLocation of Cracks In and Near WeldsLocation of Cracks In and Near WeldsLocation of Cracks In and Near Welds
Sulfuric Acid will tend to attack the heat Sulfuric Acid will tend to attack the heat affected zone (HAZ) on weld seamsaffected zone (HAZ) on weld seamsaffected zone (HAZ) on weld seams.affected zone (HAZ) on weld seams.Typically use Magnetic Particle (MT) or Typically use Magnetic Particle (MT) or DyeDye PenetrantPenetrant (PT) for finding cracks(PT) for finding cracksDye Dye PenetrantPenetrant (PT) for finding cracks.(PT) for finding cracks.
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Indirect Causes of Corrosion andIndirect Causes of Corrosion and Failure
External and Piping CorrosionExternal and Piping CorrosionExternal and Piping CorrosionExternal and Piping Corrosion
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Indirect Causes of CorrosionCorrosion behind exterior insulationCorrosion behind exterior insulationCorrosion behind exterior insulationCorrosion behind exterior insulation
Insulation material will “wick” rainwater, Insulation material will “wick” rainwater, condensation etc and hold it near thecondensation etc and hold it near thecondensation, etc., and hold it near the condensation, etc., and hold it near the tank shell, eventually leading to coating tank shell, eventually leading to coating failure and corrosion.failure and corrosion.failure and corrosion.failure and corrosion.Sulfuric acid drips and leaks can also get Sulfuric acid drips and leaks can also get trapped between insulation and tank shell trapped between insulation and tank shell t apped betwee su at o a d ta s et apped betwee su at o a d ta s ecausing dilution of the acid and causing dilution of the acid and accelerated corrosion.accelerated corrosion.
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Tank Engineering And Management Consultants, Inc.
Tank Engineering And Management Consultants, Inc.
Indirect Causes of FailureCorroded Vent Pipes and ValvesCorroded Vent Pipes and ValvesCorroded Vent Pipes and ValvesCorroded Vent Pipes and Valves
Vent piping will corrode, which could Vent piping will corrode, which could plug the vent and over pressure the tankplug the vent and over pressure the tankplug the vent and over pressure the tank.plug the vent and over pressure the tank.In the following example, a check valve In the following example, a check valve in the vent system corroded shut leadingin the vent system corroded shut leadingin the vent system corroded shut, leading in the vent system corroded shut, leading to over pressuring the tank during a fill to over pressuring the tank during a fill operation.operation.ope at o .ope at o .
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Tank Engineering And Management Consultants, Inc.
Tank Engineering And Management Consultants, Inc.
Tank Engineering And Management Consultants, Inc.
Interior Coating Inspection
Importance of Inspection Before During andImportance of Inspection Before During andImportance of Inspection Before, During, and Importance of Inspection Before, During, and after Coatings Applicationafter Coatings Application
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Interior Coating InspectionInspection Before and During CoatingInspection Before and During CoatingInspection Before and During CoatingInspection Before and During Coating
All sharp edges must be ground smooth.All sharp edges must be ground smooth.P f ti i d tP f ti i d tProper surface preparation is mandatory.Proper surface preparation is mandatory.For heat cured coatings, proper For heat cured coatings, proper t t di t t b dh d tt t di t t b dh d ttemperature gradients must be adhered to.temperature gradients must be adhered to.
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Coating failure due to improper application.Coating failure due to improper application.g p p ppg p p pp
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Tank Engineering And Management Consultants, Inc.
Interior Coating InspectionHoliday Testing InspectionHoliday Testing InspectionHoliday Testing InspectionHoliday Testing Inspection
Use NACE RP0188 for procedures and Use NACE RP0188 for procedures and standardsstandardsstandards.standards.Proper and thorough holiday test is Proper and thorough holiday test is criticalcriticalcritical.critical.A holiday test is generally not effective A holiday test is generally not effective on a coating that has already been inon a coating that has already been inon a coating that has already been in on a coating that has already been in service.service.
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Inspection Interval CalculationsAPIAPI 653 uses (T653 uses (T actact TT minmin ) /) / CorrCorr Rate toRate toAPIAPI--653 uses (T 653 uses (T actact –– T T minmin ) / ) / CorrCorr Rate to Rate to determine next inspection date. Corrosion determine next inspection date. Corrosion rate is established by previous inspectionrate is established by previous inspectionrate is established by previous inspection rate is established by previous inspection data.data.APIAPI--570 (Pipe) uses same formula, but570 (Pipe) uses same formula, butAPIAPI 570 (Pipe) uses same formula, but 570 (Pipe) uses same formula, but schedules next inspection at HALF schedules next inspection at HALF remaining life.remaining life.For severe localized corrosion applications, For severe localized corrosion applications, I prefer using the APII prefer using the API--570 method.570 method.
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SUMMARY AND CONCLUSION
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Summary
Thorough and proper inspection is critical.Thorough and proper inspection is critical.Visual inspection of both sides is extremelyVisual inspection of both sides is extremelyVisual inspection of both sides is extremely Visual inspection of both sides is extremely helpful.helpful.Use visual to guide UTM locationsUse visual to guide UTM locationsUse visual to guide UTM locations.Use visual to guide UTM locations.Don’t wait for a leak to start inspection!Don’t wait for a leak to start inspection!
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CONCLUSIONCONCLUSION
Tanks for listening!Tanks for listening!
Tank Engineering And Management Consultants, Inc.
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