MISTRAS Group BV

Hofweg 153208 LE Spijkenisse

T: +31 (0)10 245 03 25F: +31 (0)10 245 03 26

E-Mail: info@mistras.nl

Norbert TrimbornM: +31 (0)6 5278 0874

norbert.trimborn@mistras.nl

www.mistras.nl www.mistrasgroup.com

HOT HYDROGENATTACK

INspECTIONs

ExpERIENcE & REFERENcES

WWW.MISTRAS.NL

cONTAcT

Norbert Trimborn

• StudiesofAppliedPhysicsandNDT

• CertifiedinUltrasonic:

-Testinglevel3EN473,ASNTUTLIII,TOFDLIII,PALIII

• SpecialistadvancedNDT:

-TimeofFlightDiffraction(ToFD),PhasedArray(PA),

UltrasonicTesting(UT),GuidedWave(GW),Hot

HydrogenAttack(HTHA),HIC,PipeSupportInspection

• ExperienceindetectionandquantifyingofHTHAoverthe

past25years

TheinspectionmethodologydevelopedbyMistrasgivesan

absoluteindicationofthepresenceofHTHAinparentmaterial,as

longitisabovethe(lowandsafe)detectionthreshold.Decisions

canbemadeimmediately,thereisnoriskofanambiguousresult.

Ifnecessaryinordertomeasuretheprogressofattack,theinspec-

tionmethodologygeneratesdatathatcanbemonitoredveryaccu-

rately,on-line,andattemperaturesofupto450degreeCelsius.

Theinspectionmethodologyusesadvancedtechniquesincluding

TimeOfFlightDiffraction(TOFD),ultrasonicBackscatter,and

velocityratiomeasurements.Thisinspectionmethodologymeets

theHTHAinspectionapproachproposedinAPI941.

Backscatter Technique• Fastscreeningtechniqueforlargeareasthatgivesan

indicationofthepresenceofHTHA

• Note:WillnotdetectHTHAif100%ofthewallthickness

isattacked

Velocity Ratio Technique• Discriminatesbetweenindicationsresultingfrominclusions

frommanufacturing,andindicationsduetoHTHAmicro-cracks

filledwithCH4(Methane)

• Discriminates,between0%and100%attack

• Measuresextentofattack,between0%and100%ofwall

thickness

• Pointmeasurementsarecarriedout

ThepresenceofHydrogeninindustrialplantsisasourceofdamage.

HTHAisonesuchformofdegradationwhichisduetotheformation

ofMethane(CH4)byreactionwithcarboninsteel.HTHAcanoccur

eitherintheparentmaterialorinthewelditselfandmanifestsitselfin

severaltypesofalloys.

TheprobabilityofHTHAdamageinplantisdependentonthepartial

hydrogenpressure,operatingtemperature,andalloy.Methaneformed

bythereactionaccumulatesatinternalvoidsonthegrainboundaries,

whereundercertainconditionsthebuild-upcanproducemicro-cracks.

Intheweldmaterialthisleadsmostlytoaleakbeforebreaksituation

butwhenthedamageisintheparentmaterial,theresultismostly

catastrophicforpeopleandtheenvironment.

Advantages:

• SignificantreductionofriskresultsfromusingtheMistras

inspectionmethodology

• Actionscanbetakenimmediately,astheoriginof

indicationsareclassifiedwithextremelyhighreliability

• Attackcanbedetectedatanearlystagewhentheassethas

alongremaininglifetime

• Theprogressofattackcanbemonitoredaccurately

• Examinationisnon-intrusive,resultinginmajorcostsavings

• Theinspectionmethodologyisbasedonmorethan25years

oftraceableexperience.Todatenoincorrectassessments

havebeenmade

conclusions:

• TheMistrasinspectionapproachisbasedonmorethan25

yearsofexperience

• TheMistrasinspectionapproachhasbeenproventobe

reliableandreproducible

• Clearunambiguouspresentationofresults

• Allgeometriescanbeinspected

• Inspectionconformswithprocedures,usingtrainedand

certifiedOperators

HOT HydROGEN ATTAck (HTHA) ABSOLuTE dETEcTION & MONITORING AdVANTAGES & cONcLuSIONS