StandardTest Method Slow Strain Rate Test Method for Screening
Corrosion-Resistant Alloys (CRAs) for Stress Corrosion Cracking in
Sour Oilfield ServiceThis NACE International standard represents a
consensus of those individual members who have
reviewedthisdocument,itsscope,andprovisions.Itsacceptancedoesnotinanyrespect
precludeanyone,whetherhehasadoptedthestandardornot,frommanufacturing,marketing,
purchasing,orusingproducts,processes,orproceduresnotinconformancewiththisstandard.Nothing
contained in this NACE International standard is to be construed as
granting any right, by implication or otherwise, to manufacture,
sell, or use in connection with any method, apparatus, or
productcoveredbyLettersPatent,orasindemnifyingorprotectinganyoneagainstliabilityfor
infringement of Letters Patent.This standard represents minimum
requirements and should in no
waybeinterpretedasarestrictionontheuseofbetterproceduresormaterials.Neitheristhis
standard intended to apply in all cases relating to the
subject.Unpredictable circumstances may
negatetheusefulnessofthisstandardinspecificinstances.NACEInternationalassumesno
responsibilityfortheinterpretationoruseofthisstandardbyotherpartiesandaccepts
responsibilityforonlythoseofficialNACEInternationalinterpretationsissuedbyNACE
Internationalinaccordancewithitsgoverningproceduresandpolicieswhichprecludethe
issuance of interpretations by individual volunteers. Users of this
NACE International standard are responsible for reviewing
appropriate health, safety,
environmental,andregulatorydocumentsandfordeterminingtheirapplicabilityinrelationtothis
standardpriortoitsuse.ThisNACEInternationalstandardmaynotnecessarilyaddressall
potentialhealthandsafetyproblemsorenvironmentalhazardsassociatedwiththeuseof
materials, equipment, and/or operations detailed or referred to
within this standard.Users of this
NACEInternationalstandardarealsoresponsible for establishing
appropriate health, safety, and
environmentalprotectionpractices,inconsultationwithappropriateregulatoryauthoritiesif
necessary, to achieve compliance with any existing applicable
regulatory requirements prior to the use of this standard.
CAUTIONARY NOTICE:NACE International standards are subject to
periodic review, and may be revised or withdrawn at any time
without prior notice.NACE International requires that action be
takentoreaffirm, revise, or withdraw this standard no later than
five years from the date of initial publication.The user is
cautioned to obtain the latest edition.Purchasers of NACE
International
standardsmayreceivecurrentinformationonallstandardsandotherNACEInternational
publications by contacting the NACE International Membership
Services Department, 1440 South Creek Drive, Houston, Texas
77084-4906 (telephone +1 [281]228-6200). Reprinted with Minor
Editorial Changes 2004-08-19 Revised 2004-02-12 Approved 1998-02-23
NACE International 1440 South Creek Drive Houston, Texas 77084-4906
+1 (281)228-6200 ISBN 1-57590-051-3 2004, NACE International NACE
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Foreword
Failuresofmetalsexposedtohydrogensulfide(H2S)-containing(sour)oilfieldproduction
environments have been reported for more than 45 years and have
usually occurred in carbon or
low-alloysteels.1,2Failuresofhigh-strengthsteelsbybrittlecracking(sulfidestresscracking
[SSC])andoflower-strength plate and pipe steels by blistering and
hydrogen-induced (stepwise)
crackinghavealsobeenreported.Asaresult,engineersandscientistshavedevelopedtest
methods to evaluate steels for resistance to failure by these
mechanisms in sour environments. These and other considerations led
to the establishment of NACE Task Group T-1F-9 on Metallic
MaterialsTestingTechniquesforSulfideCorrosionCracking,whichdevelopedNACEStandard
TM01773 in 1977.The task group (now Task Group 085) has continued
to revise that standard.
Anadditionalinterestoftheoriginaltaskgroupwastheapplicationofcorrosion-resistantalloys
(CRAs),primarilystainlesssteelsandnickel-basedalloys,inoilfieldproductionenvironments.Some
of these materials have experienced stress corrosion cracking (SCC)
when exposed to H2S, carbon dioxide (CO2), and brine.Therefore, a
standardized method for screening CRA materials
foruseinoilfieldproductionenvironmentsisofextremeimportancetotheentirepetroleum
industry, and a work group of T-1F-9 (now Task Group 133) was
formed to address this issue.
Severalscreeningmethodswereconsideredbythetaskgroup:autoclavetestswithstatically
stressedspecimens,fracturemechanicsmethods,andtheslow strain rate
(SSR) test
technique.Eachhasadvantagesanddisadvantagesthatmaketheselectionofasingletestmethodfor
standardizationdifficult.However,overthepastseveralyears,theSSRtesthasemergedasa
relativelyquick,simplemethodthatcanbeusedfortheevaluationofmetalsandalloysfor
resistancetoavarietyofenvironmentalcrackingphenomena,includingSCC,hydrogen
embrittlement, and liquid metal cracking.1,2The use of SSR test
methods, particularly in screening
tests,hasbecomemorecommoninmanylaboratoriesforCRAevaluationfordownhole
applications.
TheSSRtestincorporatesaslow(comparedwithconventionaltensiletests),dynamicstrain
applied at a constant extension rate.Extension rates of 2.5 x 10-9
to 2.5 x 10-7 m/s (1.0 x 10-7 to
1.0x10-5in./s)arecommonlyused.Theprincipaleffectoftheconstantextensionrate,in
combinationwithenvironmentalorcorrosiveattack,istoacceleratetheinitiationofcrackingin
susceptible materials.By doing so, the SSR acts in much the same
way as a notch or precrack in
staticallystressedenvironmentalcrackingtests.Failureisobtainedwithinafewdaysfor
commonly used extension rates.
Becauseofitsrelativelyshorttestduration,theSSRtesthasbeenfoundusefulinevaluating
stainlesssteelsandnickel-basedalloysforresistancetoSCCinsimulatedoilfieldproduction
environments at elevated temperatures.4,5By comparison, it has been
observed that it may take thousands of hours of exposure time to
evaluate these materials using more conventional statically
stressed specimens.6,7 In a SSR test, the test specimen is pulled
to failure.One benefit of this method is that the ultimate
failureofthetestspecimenisapositiveresult.Thatis,parameters(includingreductioninarea
andplasticelongation)andvisualobservationscanalwaysbequantified.Theseresultsare
usuallyfurtherquantifiedbycomparisonwiththeresultsofsimilartestsconductedinaninert
environment.Acceleratingthecrackinitiationbythismechanicaltechniquetendstomakethe
SSRtestappeartobearatherseveretestbybeingabletofailmaterialsunderenvironmental
conditionsinwhichnoothertestmethod(atreasonableexposuretimes)canproducefailures.Becausetheexposuretimeisshortandthestrainratesomewhatarbitrary,theresultsofSSR
testing are not intended to be used directly to infer service
performance.It is primarily a screening or ranking method that
should be used in combination with a more extensive laboratory
evaluation
involvingcomplementarytestingforcorrosionandenvironmentalcracking.Areviewofservice
experience should be conducted before material selection decisions
are made. A round-robin testing program was conducted by former
NACE Task Group T-1F-9 during the early
developmentofthisstandardtoevaluatethevariabilityofSSRtestdataandtheinfluencesof
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varioustesting-relatedparameters.Draft#5ofthe proposed test method
was used as the basis
forthisround-robinprogramandatotalofsevencompaniesparticipated.Theresultsofthis
programindicatedthatlargedeviationsintheSSRtestdatawere observed
for some
conditions.However,uponevaluationoftheproceduresusedbytheround-robinparticipants,several
recommendationsforchangesinSSRtestproceduresweremade.Mostoftherecommended
changeswereincludedinthisstandardinanefforttoreducetheamountofdeviationinthetest
results.These changes included: (1)Ground surfaces (not turned) and
finer surface finish on the test specimen gauge section.
(2)Additional specifications regarding testing machine compliance.
(3)Improved calculation technique for reduction in area.
(4)ReferencestoindustrystandardscontainingacceptedproceduresforautoclaveandSSR
testing.
Basedontheabove-mentionedconsiderations,TaskGroupT-1F-9developedthisstandardtest
methodincorporatingtheSSR test to be used by laboratory
investigators for screening CRAs for SCC in sour oilfield
service.This NACE standard was originally developed by Task Group
T-1F-9
in1998underthedirectionofUnitCommitteeT-1FonMetallurgyofOilfieldEquipment.Itwas
revisedin2004byTaskGroup(TG)133onSlowStrainRateTestMethod.TG133is
administered by Specific Technology Group (STG) 32 on Oil and Gas
ProductionMetallurgy and
sponsoredbySTG62onScienceandEngineeringApplicationsandMethodsofCorrosion
Monitoring and Measurement.This standard is issued by NACE under
the auspices of STG 32.
InNACEstandards,thetermsshall,must,should,andmayareusedinaccordancewiththe
definitionsofthesetermsintheNACEPublicationsStyleManual,4thed.,Paragraph
7.4.1.9. Shall
andmustareusedtostatemandatoryrequirements.Thetermshouldisusedtostatesomething
goodandisrecommendedbutisnotmandatory.Thetermmayisusedtostatesomething
considered optional.
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NACE International StandardTest Method Slow Strain Rate Test Method
for Screening Corrosion-Resistant Alloys (CRAs) for Stress
Corrosion Cracking in Sour Oilfield ServiceContents
1.General..........................................................................................................................
1 2.
Reagents.......................................................................................................................
1 3. Test Specimen
..............................................................................................................
1 4. Material Properties
........................................................................................................
3 5. Test Equipment
.............................................................................................................
3 6. Environmental Test Conditions
.....................................................................................
4 7. Mechanical Test Conditions
..........................................................................................
6 8. Test
Procedure..............................................................................................................
7 9. Analysis and Reporting of Test Results
......................................................................
10
References........................................................................................................................
15 Appendix
A........................................................................................................................
16 Appendix
B........................................................................................................................
16 Figure 1: Standard SSR Test
Specimen.............................................................................
2 Figure 2: Schematic Presentation of the Possible Effects of
Strain Rate on Various Types of Cracking Behavior
............................................................................
6 Figure 3: Schematic of Typical SSR Test
System..............................................................
8 Figure 4: Typical Load-Versus-Time Plots for SSR Test of a
Ni-Fe-Cr-Mo AlloyConducted at Extension Rate of 1 x 10-7 m/s (4 x
10-6 in./s) in Several Test Environments
................................................................................................................
9 Figure 5: Schematic Illustration Based on Data for a Super-13 Cr
Stainless SteelShowing Basis for Determining the Plastic Strain to
Failure (Ep) ............................... 11 Table 1:
Description of Test Levels
....................................................................................
5 Table 2: NACE Uniform Material Testing Report FormTesting in
Accordance with NACE SSR Test
.....................................................................................................................
13
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Section 1:General 1.1ThisstandardestablishesaSSRtestmethodfor
screeningCRAmaterials(i.e.,stainlesssteelsandnickel-basedalloys)forresistancetoSCCatelevated
temperatures in sour oilfield production environments.The fact that
this test method is a screening method implies that further
evaluation or additional experience may be required before
materials selection decisions can be made.
1.2Thisstandardspecifiesreagents,testspecimen,test
equipment,determinationofbaselinematerialproperties,
environmentalandmechanicaltestconditions,test procedure, and
analysis and reporting of test results.
1.3Thetestprocedurecanbesummarizedasfollows:A
testspecimenisexposedtoacontinuouslyincreasing
uniaxialtensilestressimposedviaaslowandconstant
extensionrateinthepresenceofanacidicaqueous environment containing
H2S, CO2, and brine at an elevated
temperature.Theductilityparameters(plasticelongation
andreductioninarea)obtainedfromevaluationofthetest specimen along
with visual observation of its gauge section
andfracturesurfacemorphologyareusedasindicatorsof
thematerialsresistancetoSCCinthetestenvironment.Theseresultsarethencomparedwiththeresultsfroma
similartestconductedinaninertenvironmenttoquantify
theresistanceorsusceptibilitytoSCCinthetest environment.
1.4ProceduresforSSRtestingshallbeconsistentwith
thoseprovidedinASTM(1)G129.8Testsinvolvinghigh
pressureand/orhightemperatureshallbeperformedwith procedures
consistent with those provided in ASTM G 111.9
Theonlydeviationsfromtheseproceduresshallbethose specifically
stated in this standard. 1.5Safety Precautions
1.5.1H2Sisanextremelytoxicgasthatmustbe
handledwithextremecare.(SeeAppendixAfora
discussionofsafetyconsiderationsandtoxicityofthis gas.)
1.5.2Precautionsmustbetakentoprotectpersonnel
fromthehazardsofrapidreleaseofhotgasesand
fluidsandexplosionwhenworkingwiththehigh-pressure, high-temperature
test conditions. 1.6This standard is not intended to include
procedures for cyclic SSR testing.However, such procedures are
currently under development and are in use in some laboratories.
________________________________________________________________________
Section 2:Reagents 2.1Reagent Purity 2.1.1The gases, sodium
chloride (NaCl), and solvents
shallbereagentorchemicallypuregradechemicals.Thereasonsforthisreagentpurityarediscussedin
Appendix B. 2.1.2Thewatershallbedistilledordeionizedandof
qualityequaltoorgreaterthanASTMTypeIVin accordance with ASTM D
1193.10Tap water shall not be used.
2.2Inertgasshallbeusedforremovalofoxygen.Inert gas shall mean
high-purity nitrogen, argon, or other suitable nonreactive gas.
________________________________________________________________________
Section 3:Test Specimen
3.1Auniaxialtensiletestspecimenshallbeusedforthis
testbecauseitprovidesforasimplestressstateanda common basis for
comparison of test results.
3.1.1Thetestspecimenshallbemachinedfromthe
materialtobetestedinthemostappropriatelocation and orientation
relative to the specific evaluation being
performed.Thematerialform,however,canoften
placerestrictionsonthetestspecimenlocationand
orientation.Furthermore,thelocationandorientation of the test
specimen can affect the test results. 3.1.2The test specimen shall
be fabricated whenever
possibleinaccordancewiththeconfigurationofthe
standardtestspecimengiveninFigure1.Thelength
ofthetestspecimenhasnotbeenspecifiedto
accommodatethefollowingtwocommontest
configurations:Configuration1thetestspecimenis
entirelyenclosedinthetestvesselwithmetalgrips (pull rods) passing
through the ends of the test vessel; ___________________________(1)
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andConfiguration2thetestspecimenshoulder
sectioniselongatedtopassthroughtheendsofthe
testvesselwithouttheuseofgrips(pullrods)that extend inside the test
vessel. mmin. L125.41.00 L2NS*NS* D13.810.150 D26.350.250 R6.35
min.0.250 min. TNSNS ThreadNSNS * NSNot Specified FIGURE 1 Standard
SSR Test Specimen 3.1.2.1Thegaugesectionofthetestspecimen
shallhavethefollowingdimensions:3.81mm
(0.150in.)diameter(D1)and25.4mm(1.00in.) length (L1).
3.1.2.2Theradiusofcurvature(R)ofthe shoulder section at the ends of
the gauge section shallbeatleast6.35mm(0.250in.)tominimize stress
concentrations and fillet failures.
3.1.2.3Theoveralllengthofthetestspecimen
(L2)isatthediscretionoftheuserbasedonthe test configuration
desired. 3.1.3Ifmaterialsizeorshapedictatestheuseofa
testspecimenotherthanthosegiveninParagraph
3.1.2,detailsofthealternativegeometrymustbe
providedwiththetestresults.Theuseriscautioned
thatthecalculationsofextensionrate,crosshead displacement rate, and
nominal strain rate used in this standard are predicated on the
standard gauge section length specified in Paragraph 3.1.2 and
Figure 1. 3.2Machining
3.2.1Thetestspecimenmustbefabricatedcarefully
toavoidoverheatingandunnecessary cold working of
thegaugesection.Thesurfaceroughnessofthe gauge section shall be
0.25 m (10 in.) or finer.The
preferredmethodofmachiningthegaugesectionof
thetestspecimenshallbebygrinding.Thismethod has been shown to
completely avoid localized grooves
andcold-workedareas.Alternativemethodsof
machiningthetestspecimengaugesectionmaybe
usediftheyhavebeenshowntoproducesimilartest
resultsasobtainedundersimilarconditionsfromtest
specimensinwhichthegaugesectionhasbeen
preparedbygrinding.Theremainderofthetest
specimenmaybefabricatedusingconventional methods.
3.2.2Thefinaltwomachiningpassesonthegauge section should remove no
more than a total of 0.05 mm (0.002 in.) of material.
3.2.3Thegaugesectiondiametershallbeuniform within 0.127 mm (0.005
in.) tolerance.The minimum diametershouldbeinthecenterofthegauge
section with no undercutting of the shoulder radii. Mengfei Guo -
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3.3.1Stamping or vibratory stenciling may be used on
theendsorshouldersectionofthetestspecimenbut not in the gauge
section of the test specimen. 3.4Cleaning
3.4.1Beforetesting,thetestspecimenshallbe degreased in a
nonchlorinated solvent and rinsed with acetone.
3.4.2Thegaugesectionofthetestspecimenshould not be handled or
contaminated after cleaning. 3.4.3All apparatus used in the test
shall be cleaned to ensure an absence of contaminants.
________________________________________________________________________
Section 4:Material Properties
4.1Toassessrepeatabilityofmeasurement,atleasttwo tests in air
should be conducted.In this case, the average value of the
parameters shall be used.However, significant
variationsbetweenthetwoormoresetsofdatawould
suggestmaterialinhomogeneityorproblemswiththetest
equipmentandshouldbeinvestigated.Atleastonetest
specimenshallbepulledinairorothersuitablyinert
environmentundersimilarconditionsoftemperatureand extension rate
and with the same type of test specimen and loading equipment as
those used in the environmental tests
describedinthisstandard.Theresultsfromthistestshall
beusedasthebaselinematerialpropertiesfortheyield
strength,ultimatetensilestrength,timetofailure, elongation, and
reduction in area. 4.1.1Thetestspecimenstobeusedfordetermining
baselinematerialpropertiesshouldbemachinedfrom
adjacentlocationsinthematerialandinthesame
positionandorientationasthetestspecimenstobe
testedintheenvironmenttominimizevariationinthe properties of the
test specimens. 4.1.2Alltestsonaparticularmaterial shall be run on
the same set of test equipment.
4.1.3Theresultsofthesetestsmaynotproducethe
samematerialpropertydataasconventionaltensile
testsperformedwithtestspecimensofdifferentsizes or geometry or at
different strain rates.
4.2Becausemechanicalpropertiescanvarythroughthe thickness of the
material, depending on the material history (e.g., cold-worked
rod), hardness measurements should be
takentoensureconsistencyinbasicpropertiesforthe
differenttestspecimens.Thesehardnessmeasurements
shallbemadebyconductinghardnessscansonthebase
materialorbymeasurementontheblankspriorto
specimenpreparation.Hardnessmeasurementsshallnot be made on the
gauge section of the test specimen.
4.3Anumberofmaterialpropertiesmaycorrelatewith
SCCperformance.Consequently,allpertinentdataon
chemicalcomposition,meltingpractice,conventional
mechanicalproperties,heattreatment(e.g.,aging),and mechanical
history (i.e., percent cold reduction or prestrain) shall be
included with the tensile test data indicated above.
4.3.1Eachheattreatmentandmicrostructureofthe material of a fixed
chemical composition shall be tested as though it were a different
material.
________________________________________________________________________
Section 5:Test Equipment 5.1Test Vessels
5.1.1Thetestvesselsshallbemadeofcorrosion-resistantmaterialsthatareeffectivelyinertinthetest
environment. 5.1.2Testvesselsshallberatedtoanadequate
workingpressuretopermitsafeoperationatthe temperature and pressure
conditions of the test. 5.1.3Testvesselsshallbecapableofbeingpurged
withgasesbeforetestingandresistanttoleakage during the test.
5.1.4Testvesselsshallbesizedtomaintainthe
solution-volume-to-exposed-test-specimensurface area ratio at
greater than 0.3 mL/mm2.
5.1.5Testvesselsandassociatedfixturesshallbe
electricallyinsulatedfromthetestspecimensifthe vessels and fixtures
are made from metals dissimilar to the test specimens.This can
usually be accomplished
usingnonmetallic(polymericorceramic)bushings, coatings, and/or
seals. 5.1.5.1Rigidinsulatingmaterialsthatdonot relax or flow under
load when they are involved in stressing the test specimen shall be
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vessels for use with Configuration 1 test
specimensshallbedesignedwithpullrodstoallow entryintothe test
vessel for application of load on the test specimen while
simultaneously maintaining a
seal.ThetestvesselsforusewithConfiguration2test
specimensshallbedesignedtomaintainaneffective
sealontheshoulderportionofthetestspecimen.Seals with low frictional
characteristics shall be used to
maintainaccurateapplicationofloadonthetest specimen. 5.2Test
Specimen Grips 5.2.1Test specimen grips that load the test specimen
shall be used. 5.2.2Thetestspecimengripsshallbeelectrically
isolatedfromthetestspecimenifthegripsaremade
frommetalsdissimilartothetestspecimens.Alternatively,acceptablenonconductivecoatingsthat
canwithstandthetestenvironmentandmechanical
loadmaybeusedtoisolatethegripsfromthetest environment.
5.2.3Threaded grips exposed to the test environment
shallbeventedtoallowforremovalofentrappedair
duringthedeaerationprocedure.Airentrapmentin threaded grips has
been shown to increase the severity
ofcorrosionandcrackingintestsconductedinsour environments.
5.3Testing Machines 5.3.1Testingmachinesshallbecalibratedand
maintainedtoensuretheaccuracyoftheextension
rate.Theextensionrateshallbewithin2%ofthe intended extension rate.
5.3.2Onlythosetestingmachinesthathavebeen
showntoprovidereliableandreproducibleapplication
ofloadattheintendedextensionrate(typically2.5x 10-9 to 2.5 x 10-7
m/s [1.0 x 10-7 to 1.0 x 10-5 in./s]) shall be used to conduct this
test. 5.3.3For the SSR testing machine used, the slope of
theload-versus-timeplotshouldbemeasured using a
specimenblank(withnogaugesection)inwhichthe
displacementislimitedtothatofthetestingmachine
anditscomponents.Theslopeofthisplotgivesan indication of the system
compliance.Differences in the compliance of various testing
machines or components canleadtovariationsinSSRtestresults.Inmost
cases, these variations can be minimized by using the ratios
described in Paragraph 9.3.5 and by conducting air and environment
tests on the same testing machine or on machines with similar
compliance. 5.3.4Testingmachinesthatpullasingletest
specimenarepreferredbecauseloadframesthattest
multiplespecimensmayimpartshockloadingtothe
remainingtestspecimenswhenoneormoretest specimens fail.Multiple
specimen load frames may be
utilizedonlyifeachtestspecimenhasaseparate loading mechanism or if
it has been demonstrated that
failureofoneormoretestspecimensdoesnot
influencetheresultsfromothertestspecimensunder test at the same
time.
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Section 6:Environmental Test Conditions 6.1The test environment,
including the exact temperature,
pressure,andcompositionoftheaqueousandgaseous phases, must be
specified and recorded. 6.1.1There are two common approaches
employed in SSR testing programs for screening CRA materials for
petroleum applications. 6.1.1.1When CRA materials are to be
evaluated foraspecificserviceapplication,thetest
environmentthatmostcloselysimulatesthe
corrosiveenvironmentfoundinthatspecific
serviceapplicationisspecified.Inthiscase,a
varietyofindividualalloysrepresentingvarious types of CRA materials
are then tested to evaluate their relative performance for that
particular service environmenttoaidinreachingafinalmaterials
selection decision. 6.1.1.2When a number of individual alloys
within a specific type of CRA material are to be evaluated as part
of a general screening exercise, a suitable
testenvironmentthatprovidesappropriate
discriminationofperformanceisselected.Inthis
case,therelativeperformanceofindividualalloys in a general
environment can be evaluated, but the
resultsmaynotbeapplicabletoadifferent
corrosiveserviceenvironment.Table1liststest
levelsforevaluationofmaterialsforsourservice
asshowninNACEStandardMR017511under
proceduresforadditionofnewmaterialsor
processes.Thetestlevelsprovidedinthistable
arenotmandatorytestconditionsandarenot
intendedtorepresentactualserviceconditions.Theyareprovidedtotheuserofthisstandardas
guidance,particularlyifthematerialorprocess
beingevaluatedisballotedforinclusioninNACE Standard MR0175.
6.1.2Bothaqueousandgaseousphasesshallbe present at the specified
test temperature and pressure. 6.2Aqueous Phase Mengfei Guo -
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of the test environment shall
consistofabrinesolutionofspecifiedcomposition.Distilledordeionizedwatershallbeusedtoprepare
thebrinesolution.Theaqueousphaseofthetest
environmentshouldconsistofapproximately80%of the autoclave volume
at the intended test conditions.
6.2.2Sodiumbicarbonateissometimesaddedto
simulatethebicarbonatebufferingfoundinsome
producedformationwater.Itgenerallyincreasesthe
aqueousphasepHandcandecreasetheseverityof
thetestenvironmentfromthestandpointofSCC.Sodium bicarbonate, added
in solid form, is an optional constituent of test environments (see
Table 1other). 6.2.3Elemental sulfur is sometimes added to simulate
severesourconditions,especiallyinconjunctionwith
veryhighH2Spartialpressure.Thepresenceof elemental sulfur generally
increases the severity of the
testenvironmentfromthestandpointoflocalized
corrosionandSCC.12,13Elementalsulfur,addedin
powderedforminamountsupto1g/Lofaqueous
phase,isanoptionalconstituentoftestenvironments (see Table 1other).
6.3Gaseous Phase 6.3.1The gaseous phase of the test environment
shall consist of a mixture of H2S, CO2, and water vapor and
mayalsocontainnitrogen,methane,orinertgas,as required, to reach the
intended total pressure. 6.3.2Thegaseousphaseshallbecharacterizedin
termsofthepartialpressure([totalabsolutepressure
minussolutionvaporpressure]timesmolefraction)of H2S and CO2 at the
test temperature and pressure.
6.3.3ThepartialpressureofH2SandCO2shallbe
maintainedwithin10%ofthespecifiedvalues.The
actualconcentrationofeachgasmaybedetermined
byavarietyofanalyticalmethods.Acommon
procedureistouseamassbalanceasdetailedin Appendix B. 6.4Test
Temperature 6.4.1Thetemperatureofthesolutioninthetestcell
shallbemaintainedto3C(5F)of the specified test
temperature(theaveragevalueduringthetest)for
near-ambienttemperaturetestingand5C(9F)for
elevatedtemperatures(typically,90C[194F]and above). TABLE 1
Description of Test Levels Test LevelIIIIIIIVVVIVII Temperature25
3C (77 5F) 25 3C (77 5F) 25 3C (77 5F) 90 5C (194 9F) 150 5C (302
9F) 175 5C (347 9F) 205 5C (401 9F) CO2 partial pressure, min.
nonenonenone700 kPaabs (101 psia; 6.9 bara) 1,400 kPaabs (203 psia;
13.8 bara) 3,500 kPaabs (508 psia; 34.5 bara) 3,500 kPaabs (508
psia; 34.5 bara) Test Environment H2S partial pressure, min.
(list)TM0177TM01773 kPaabs (0.435 psia; 0.03 bara) 700 kPa abs (101
psia; 6.9 bara) 3,500 kPa (508 psi; 34.5 bar) 3,500 kPaabs (508
psia; 34.5 bara) NaCl content, min. (list)TM0177TM017715%15%20%25%
pH(list)TM0177TM0177 Other(list)nonecoupled to steel
(list)(list)(list)(list) Test Method(s) (list)(list the TM0177
method) (list the TM0177 method) (list)(list)(list)(list) Material
Type and Condition describechemical composition, UNS number,
process history Material Properties describeyield strength, tensile
strength, % elongation, hardness Stress Level and Results
describetest stress level, plastic strain, etc., test results
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Section 7:Mechanical Test Conditions 7.1Extension Rate
7.1.1Thesensitivityofcorrosion-resistantalloysto
hydrogenembrittlementorsulfidestresscrackingis
strain-ratedependentasillustratedschematicallyin Figure2.14
Accordingly, the absence of embrittlement in a constant extension
rate test at a specific strain rate should not be considered as
indicating that the alloy is
fitforservice;failuremaystilloccuratalowerstrain
rate.Themethodisdesignedprimarilyforranking purposes and while
in-house acceptance criteria exist, there is no general consensus.
7.1.2Forranking/screeningpurposes,thechoiceof
strainrateisdesignedtoensurethatthetestis
sufficientlydiscriminating,reasonablyrapid,andgives
acceptablerepeatabilityandreproducibility.Intrinsically,theoptimumstrainratemaybealloy-dependent.Experiencehassuggestedthatastrain
rateof1x10-6s-1givessatisfactoryresultsformany systems, e.g.,
modified 13 Cr steels.When more rapid assessment is required, a
strain rate of 4 x 10-6 s-1 may
beadopted.Thestrainrateof4x10-6s-1cangive
satisfactoryresultsfornickelandausteniticalloys,but for other
systems this may lead to reduced repeatability
andreproducibility.Careshouldbetakentoensure
thatthetestremainssufficientlydiscriminatingforthe purpose. Case
1Stress Corrosion Cracking Case 2Hydrogen Embrittlement or Sulfide
Stress Cracking FIGURE 2 Schematic Presentation of the Possible
Effects of Strain Rate on Various Types of Cracking Behavior
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Section 8:Test Procedure 8.1Test Specimen/Test Vessel Assembly
8.1.1Thegaugesectiondiameter(D1)ofthetest specimen shall be
measured to the nearest 0.025 mm (0.0010 in.) and the value shall
be recorded. 8.1.2Thetestspecimengripsandtheinternal
surfacesofthetestvesselshallbecleanedand
degreased.Careshouldbetakenthereafternotto
handleorcontaminatethegaugesectionofthetest specimen or the test
vessel. 8.1.3Thetestvessel,testspecimen,andgripsshall be
assembled.If the test vessel and the test specimen are dissimilar
materials, electrical isolation between the test specimen/grip
assembly or test specimen and the
testvesselshallbemaintainedtopreventgalvanic
effects.Thisisolationshouldbecheckedwithan ohmmeter prior to and
after testing. 8.1.4Thetestspecimen/gripassemblyortest
specimenshallbealignedwiththetestvesselports
(topandbottom).Alignmentproceduresareprovided in ASTM E 8/E 8M.15
8.2Test Environment Make-Up
8.2.1Theaqueousphase(brinesolution)shallbe deaerated with inert gas
(nitrogen, argon, etc.) prior to
additiontothetestvessel.Thedeaeratedbrine
solutionshallbepreparedinasealedvesselthatis purged with inert gas
for at least 1 h/L of solution at a rate of 100 mL/min.
8.2.2Theaqueousphaseshallbetransferredtothe
testvessel,whichshallbedeaeratedpriortotransfer.Inthelattercase,cyclicapplicationofvacuum(less
than29mmHg)andinertgaspurging(atleasttwo
cycles)providesthemosteffectivemethod.Inertgas purging of the test
vessel can also be effective.If the
deaeratedtestsolutionistransferredintothetest
vesselunderinertgas,nofurtherdeaerationis
necessary.However,redundantdeaeration
proceduresshouldbeusedtoremoveanyoxygen
contaminationthatmayoccurduringthesolution transfer.
8.2.2.1Ifarotaryoilpumpisusedtoobtain vacuum, an oil mist trap
shall be applied between thevacuumpumpandthetestvesseltoprevent oil
contamination in the test.
8.2.3Uponcompletionofthepurging,thetestvessel shall be pressurized
with inert gas to the specified test
pressuretocheckforleakagefromtubing,valves, fittings, and seals.
8.2.3.1Asimpleprocedureforthischeckis application of a mild soap
solution to these areas.Soap bubbles indicate leakage of gas.
8.2.4Theinertgaspressureshallbereleased;then the test gas(es) shall
be added to the test vessel. 8.2.4.1Thegasinthetestvesselmustbe
allowedtoequilibratewiththeaqueousphase.This requires bubbling of
the gas into the aqueous phaseoragitationofthetestvessel.Either
procedure should be conducted at the starting test pressure.
8.2.4.1.1IfpartialpressureH2Senviron-ments below 100 kPa abs (15
psia) are used, thetestvesselshallbeevacuated to remove the inert
gas prior to adding the test gas(es).
8.2.4.2ToobtainH2Spartialpressuresabove
100kPaabs(15psia),liquidH2Smaybeadded on a weight basis.A specified
number of grams of liquid H2S can be added to the test vessel using
a smalltransferpressurevesselthatisweighedto
thenearest0.1gbeforeandafterfilling.This
procedureaddstheweightoftheconstituent needed to produce the
necessary partial pressure under the test conditions.
8.2.4.3Adjustments to achieve the specified test
pressuremaybemadeafterheatingthetest vessel to the desired test
temperature for a single-componentgasphase;however,such adjustments
should not be made for gas mixtures.
8.2.4.4WhenaddinggasescontainingH2S,the
testvesselshallbepressurizedinaventilated laboratory hood.
8.2.5Afterfillingthetestvesselwiththetest environment, any excess
H2S-containing gas should be
releasedthroughasuitablescrubbingsystemto neutralize the H2S.
8.3Testing Machine Set-Up 8.3.1The test vessel containing the test
specimen and testenvironmentshallbeplacedinthetesting
machine.AschematicdrawingofatypicalSSRtest system is given in
Figure 3. 8.3.1.1RefertoAppendixAforguidelineson safely conducting
tests using H2S gas.
8.3.2Thezeropointandcalibrationoftheload-monitoringsystemshallbecheckedandsetforthe
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8.3.3Precautionsshallbetakentopreventthetest specimen from being
compressively loaded by thermal expansion during the heating
operation. 8.3.3.1Atensilepreloadof230to450N(50to
100lb)shouldbeappliedtothetestspecimen prior to heating.This may be
done manually or by using the drive mechanism of the testing
machine. 8.3.3.2Duringheating,thepreloadonthetest
specimenshouldbemonitoredtoensurethatit
doesnotdecreasetozeroorbecome compressive.
8.3.4Duringheating,thepressureinthetestvessel
shouldbemonitoredandcontrolled,ifnecessary,so
thatitdoesnotincreasebeyond the working pressure limits of the test
vessel. 8.3.5Beforestartingthetest,thepressureinthetest
vesselshouldbemonitoredandcontrolled,if necessary, to achieve the
specified test pressure. FIGURE 3 Schematic of Typical SSR Test
System 8.4Test Initiation 8.4.1Before starting the test, a preload
of 230 to 450 N (50 to 100 lb) shall be established. 8.4.2Thetest
temperature and test pressure shall be recorded immediately before
testing. 8.4.3Thetestingmachineshallbeactivatedtostart loading the
test specimen at the desired extension rate. 8.5Test Period
8.5.1Datashallberecordedcontinuouslythroughout
thetestperiodwithasuitablycalibratedstripchart recorder or x-y
recorder, or at frequent intervals of time
usingsuitabledataacquisitionequipmentthatpermits
displayoftheloadorstressonthetestspecimen
versustime,displacement,orstrain.Figure4shows typical
load-versus-time plots for SSR tests. Mengfei Guo - Invoice
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International9 (A) Test conducted in air. FIGURE 4 Typical
Load-Versus-Time Plots for SSR Test of a Ni-Fe-Cr-Mo Alloy
Conducted at Extension Rate of 1 x 10-7 m/s (4 x 10-6 in./s) in
Several Test Environments 8.6Termination of Test
8.6.1Thetestshallbeconsideredterminatedwhen
fractureofthetestspecimenisobservablebya decrease in the load on
the test specimen to near zero.
8.6.1.1Oncethetestspecimenhasfractured,
caremustbetakentorestraintheendsofthe
failedtestspecimenuntilthepressurehasbeen bled off from the test
vessel.This restraint may be
performedeitherinsidethetestvesselorbythe
testingmachineloadframe.Failuretoobserve this procedure may result
in the failed ends of the test specimen being ejected from the test
vessel at highvelocityandreleaseofpressureandH2S-containing gas.
8.6.2Gas pressure in the test vessel shall first be bled off to the
brine solution vapor pressure and then cooled to 38 to 66C (100 to
150F).Cooling the test vessel at test pressure can result in sudden
unexpected leakage. 8.6.2.1AllH2S-containinggasesandsolutions
shallbeneutralizedbyasuitablescrubbing system prior to disposal.
8.6.3The test vessel shall be purged with inert gas to remove any
residual H2S to a safe level.
8.6.4Thetestvesselshallbeopenedandthetwo
sectionsofthetestspecimenremoved.Thisshallbe performed in a
laboratory hood under proper ventilation to reduce the risk of
exposure to any residual H2S.
8.6.5Thetestspecimenshallberinsedwithdistilled water and dried.
8.6.6The test specimen shall be stored in a desiccator or other
suitable noncorrosive environment until further evaluation or
analysis is conducted. H2S CO2SClT kPa abspsiakPa abspsiag/L%CF
A(A)------204400 B2,80040000015204400 C2,8004005,500800115204400
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Section 9:Analysis and Reporting of Test Results
9.1Twobasictypesofresultsshallbeobtainedfromthis SSR test:
(1)Visualexaminationofthetestspecimengauge section for evidence of
cracking. (2)Measurementsoftheductilityparametersofthetest
specimenandcomparisonwiththe baseline material properties
determined in air. 9.2Visual Examination
9.2.1Bothhalvesofthefailedgaugesectionofthe test specimen shall be
visually examined under a low-power optical microscope at a
magnification of at least 20X.
9.2.2Basedonthevisualexamination,oneofthe following classifications
shall be assigned: Class1Normalductilebehavior(comparablewitha
specimen tested in air) with no indication of SCC on the
primaryfracturesurface,andnoindicationof secondary cracking.
Class2Ductilebehaviorwith only slight loss (20%)ofductilityfrom
that of air test.Fissures may develop in the necked region
ofthegaugesectionimmediatelyadjacenttothe primary fracture surface,
but no indication of SCC. Class4EvidenceofSCCinthegaugesectionby
observationofSCContheprimaryfracturesurface and/or secondary
cracking in the gauge section.
9.2.3Metallographicsectioningofthetestspecimen
gaugesectionandobservationat100Xorscanning
electronmicroscopymaybeconducted,ifdesired,to
morefullycharacterizethefailedtestspecimenswith
respecttoSCCbehavior.Thismethodishelpfulin
identifyingClass2orClass3testspecimensas defined in Paragraph
9.2.2. 9.3Evaluation of Ductility Parameters
9.3.1Twoductilityparametersshallbeusedin
evaluatingtheresultsoftheSSRtest:(1)elongation
and(2)reductioninarea.Totaltimetofailureshould
bemeasuredforcomparisonpurposes.Actualtest
specimenelongationcanbemeasuredbasedonits physical extension;
however, this measurement should not be relied on for quantitative
determination. 9.3.2Thechangeincross-sectionalareaofthetest
specimenforcircularfracturesshallbecalculatedas shown in Equation
(1): 100 x DD-D= (%) RA 2I2F2I(1) Where:RA=Reduction in area (%)
D=Initial gauge section diameter in mm (in.) DF=Final gauge section
diameter atfracture location in mm (in.)
9.3.2.1Fornoncircularfracturesurfaces,the change in cross-sectional
area shall be calculated as shown in Equation (2): 100D)] C x(C
-D[= (%) RA 2IFB FA2I (2) Where:CFA=Major axis of fracture surface
in mm (in.) CFB=Minor axis of fracture surface in mm (in.)
9.3.3Thetestspecimenelongationshallbedefined
asthetotalplasticelongationofthetestspecimenat failure.
9.3.3.1Theplasticstraintofailure(EP)shallbe
determinedfromtheload-versus-timeorload-versus-elongationcurvebysubtractingtheelastic
strain at failure from the total strain at failure (see Figure
5).Mengfei Guo - Invoice INV-293193-TFRMKS, downloaded on 1/7/2010
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prohibited.TM0198-2004 NACE International11 0.00 0.05 0.10 0.15
0.200200400600800EtotEelEp -1100 mV in 3.5 wt% NaCl Test in
airStress (MPa)Strain FIGURE 5 Schematic Illustration Based on Data
for a Super-13 Cr Stainless Steel Showing Basis for Determining the
Plastic Strain to Failure (Ep)
Thisparameterhasbeenadoptedbecause,inmost
testing,thedisplacementofthegaugesectionisnot measured
directly.Rather, the crosshead displacement is
measured,andthisincludesacontributionfromthe displacement of the
shoulders of the test specimen and of
theloadtrain.Becausethesecanvaryfromonetest
systemtoanother,thecalculatedstrainonthegauge section of the test
specimen at any time is sensitive to the
testsystem.Theactualstrainrateonthegaugesection
intheelasticloadingregionalsovariesfromonetest
systemtoanother,despitesimilarvaluesofthenominal
strainrate.However,onceyieldingoccurs,mostofthe
increaseindisplacementinthecrossheadisassociated
withtheplasticdeformationofthegauge section and the
differencesbetweentestsystemsshouldbeless
significant.Accordingly,forthosesystemsthatfail
beyondyield,meaningfulcomparisonofdatacanbe made by use of the
plastic strain to failure.
9.3.3.2Ifaload-versus-timecurveisused,EPshall be calculated using
Equation (3): 100LXTLXT= (%)EIPLPLFIFP (3) Where:EP=Plastic strain
to failure (%) X=Extension rate in mm/s (in./s) TF=Time to failure
in seconds TPL=Time to proportional limit in seconds LI=Initial
gauge length, in mm (in.) (usually 25.4 mm [1.00 in.]; see
Paragraph3.1.3)F=Stress at failure PL=Stress at proportional limit
NOTE:Forthecaseinwhichthestressat proportional limit (PL) and the
stress at failure (F) are equivalent, (i.e., no work hardening or
necking priortofailure)theterm [F/PL] in Equation (3) is
equaltooneandcanbeeliminatedfromthe equation.
9.3.3.3Ifaload-versus-elongationcurveisused,EP shall be calculated
using Equation (4): 100 x LExLE(%) EIPLPLFIFp = (4)
Where:EP=Plastic strain to failure (%) EF=Elongation at failure in
mm (in.) EPL=Elongation at proportional limitin mm (in.) Mengfei
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NOTE:Forthecaseinwhichthestressat proportional limit (PL) and the
stress at failure (F) are equivalent, (i.e., no work hardening or
necking priortofailure)theterm [F/PL] in Equation (4) is
equaltooneandcanbeeliminatedfromthe equation.
9.3.4Theplasticstrainatmaximumload (Epmax) shall also be
calculated.Using Equation (3), max (maximum
stress)maybesubstitutedforFandTmax(timeto maximum load) may be
substituted for TF.In Equation (4), max may be substituted for F
and Emax (elongation at maximum load) may be substituted for EF.
9.3.5Thecomparisonoftheductilityparameters
determinedinthetestenvironmentwiththose
determinedinairshallbeconductedusingthe following ratios in
Equations (5) and (6): 100 x EE= R(%) EpApEp(5) Where:EpR=Plastic
strain-to-failure ratio EpA=Plastic strain to failure in air
EpE=Plastic strain to failure in the testenvironment 100 RARA=
RAR(%)AE (6) Where:RAR=Reduction in area ratio RAA=Reduction in
area in air RAE=Reductioninareaintest environment
9.3.6Ductilityratios(i.e.,plasticstrain-to-failureratio
[EpR]andreductioninarearatio[RAR])near100
generallyindicatehighresistancetoenvironmental
cracking,whereaslowvaluesgenerallyindicatelow resistance to
environmental cracking.
9.3.7Testresultsshallbereportedonareportform similar to that shown
in Table 2. Mengfei Guo - Invoice INV-293193-TFRMKS, downloaded on
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Uniform Material Testing Report Form (Part 1)Testing in Accordance
with NACE SSR Test Submitting Company Submittal Date Submitted
byTelephone No.Testing Lab Alloy Designation General Material Type
(A) Melt Practice:open-hearth (OH), basic oxygen furnace (BOF),
electric furnace (EF), argon-oxygen decarburization (AOD). (B)
e.g., cold work, plating, nitriding, prestrain, etc. ChemistryHeat
Number/Identification C Mn P S Si Ni Cr Mo V Al Ti Nb N Cu Other
MaterialProcessing HistoryMelt Practice (OH, BOF, EF, AOD.(A))
Product Form Heat Treatment (Specify time, temp., and cooling mode
for each cycle in process.) Other Mechanical, Thermal, Chemical, or
Coating Treatment(B) Mengfei Guo - Invoice INV-293193-TFRMKS,
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TABLE 2 (continued) NACE Uniform Material Testing Report Form (Part
2)Testing in Accordance with NACE SSR Test Material Specimen
Geometry: Standard Nonstandard Specimen mounting configuration (see
Paragraph 3.1.2): Gauge DiameterGauge Length EnvironmentIII
IIIIVVVIVIIOther (specify) Partial pressure H2S (kPa abs [psia])
Extension RatePartial pressure CO2 (kPa abs [psia]) Total
PressureTemperatureNaCl (wt%)Sulfur (g/L) Bicarbonate (g/L) Other
Material Identification Location(A) Orientation(B) Properties in
Air Values in Environment SSR Ratio(D) Visual Rating (Class)(E)
Y.S.(C) U.T.S. Ep (%) RA (%) Hard- ness Ep (%) RA (%) Epmax (%) EpR
(%) RAR (%) Remarks (A) Location of test specimen taken from test
piece may be OD, mid-radius (MR), center (C), or edge (E). (B)
Orientation may be longitudinal (L), or transverse (T). (C) Yield
strength is assumed to be at 0.2% offset unless otherwise noted.
(D) See Paragraph 9.3.5. (E) See Paragraph 9.2.2. Mengfei Guo -
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References 1.G.Ugiansky,J.H.Payer,eds.,StressCorrosion Cracking:
The Slow Strain Rate Technique, ASTM STP 665 (West Conshohocken,
PA: ASTM, 1979). 2R.D.Kane,ed.,SlowStrainRateTestingforthe
Evaluation of Environmentally Induced Cracking:Research
andEngineeringApplications,ASTMSTP1210(West Conshohocken, PA:ASTM,
1993). 3.NACEStandardTM0177(latestrevision),Laboratory Testing of
Metals for Resistance to Sulfide Stress Cracking
andStressCorrosionCrackinginH2SEnvironments (Houston, TX:NACE
International). 4.D.R.McIntyre,R.D.Kane,S.M.Wilhelm,SlowStrain
RateTestingforMaterialsEvaluationinHighTemperature H2S
Environments, Corrosion 44, 12 (1988):p. 920.
5.A.I.Asphahani,SlowStrainRateTechniqueandits Application to the
Environmental Stress Cracking of
Nickel-baseandCobalt-baseAlloys,inASTMSTP665,Stress
CorrosionCracking: The Slow Strain Rate Technique, eds.
G.M.Ugiansky,J.H.Payer(WestConshohocken,PA: ASTM, 1979):pp.
279-293. 6.R.D. Kane, et al., Stress Corrosion Cracking of
Nickel-BaseAlloysinChlorideContainingEnvironments
CORROSION/79,paperno.174(Houston,TX:NACE, 1979).
7.G.A.Vaughn,J.B.Greer,High-StrengthNickelAlloy Tubulars for Deep,
Sour Gas Well Applications, 1980
SPE-AIMEAnnualMeeting,paperno.9240(Richardson,TX:SocietyofPetroleumEngineers[SPE](2))(NewYork,NY:
AmericanInstituteofMining,Metallurgical,andPetroleum Engineers
[AIME],(3) 1980). 8.ASTMG129(latestrevision),StandardPracticefor
SlowStrainRateTestingtoEvaluatetheSusceptibilityof
MetallicMaterialstoEnvironmentallyAssistedCracking (West
Conshohocken, PA:ASTM). 9.ASTMG111(latestrevision),StandardGuidefor
CorrosionTestsinHighTemperatureorHighPressure Environment, or Both
(West Conshohocken, PA:ASTM). 10.ASTM D 1193 (latest revision),
Standard Specification for Reagent Water (West Conshohocken,
PA:ASTM). 11.NACEStandardMR0175(latestrevision),Metalsfor
SulfideStressCrackingandStressCorrosionCracking
ResistanceinSourOilfieldEquipment(Houston,TX:NACE).
12.S.M.Wilhelm,EffectsofElementalSulfuronthe
StressCorrosionCrackingofNickel-BaseAlloysinDeep Sour Gas Well
Production, CORROSION/88, paper no. 77 (Houston, TX:NACE, 1988).
13.A.Miyasaka,K.Denpo,O.Hiroyuki,Environmental
AspectsofSCCofHighAlloysinSourEnvironments, CORROSION/88, paper no.
70 (Houston, TX: NACE, 1988).
14.C.D.Kim,B.E.Wilde,AReviewoftheConstant
Extension-RateStressCorrosionCrackingTest,inASTM STP 665, Stress
Corrosion Cracking: The Slow Strain Rate
Technique,eds.G.M.Ugiansky,J.H.Payer(West Conshohocken, PA: ASTM,
1979):pp. 97-112. 15.ASTME8/E8M(latestrevision),StandardTest
MethodsforTensionTestingofMetallicMaterials(West Conshohocken, PA:
ASTM). 16.OSHA(4)RulesandRegulations,FederalRegister37, No. 202,
Part II (Washington, DC:OSHA, 1972).
17.N.IrvingSax,DangerousPropertiesofIndustrial Materials (New York,
NY:Reinhold Book Corp., 1984).
18.DocumentationoftheThresholdLimitValues
(Cincinnati,OH:AmericanConferenceofGovernmental Industrial
Hygienists, Inc.). 19.PublicationNU81-123,NIOSH(5)/OSHAOccupational
Health Guidelines for Chemical Hazards, Superintendent of
Documents,U.S.GovernmentPrintingOffice, Washington, DC.
___________________________(2) Society of Petroleum Engineers
(SPE), 222 Palisades Creek Drive, P.O. Box 833836, Richardson, TX
75083-3836. (3) American Institute of Mining, Metallurgical, and
Petroleum Engineers (AIME), Three Park Ave. (17th Floor), New York,
NY 10016-5998. (4) Occupational Safety and Health Administration
(OSHA), 200 Constitution Ave. NW, Washington, DC 20210. (5)
National Institute for Occupational Safety and HealthCenters for
Disease Control and Prevention (NIOSH), 1600 Clifton Rd., Atlanta.
GA 30333. Mengfei Guo - Invoice INV-293193-TFRMKS, downloaded on
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Appendix A Safety Considerations in Handling H2S Toxicity
H2Sisperhapsresponsibleformoreindustrialpoisoning
accidentsthananyothersinglechemical.Anumberof these accidents have
been fatal.H2S shall be handled with
cautionandanyexperimentsusingitshallbeplanned
carefully.Themaximumallowableconcentrationintheair
foraneight-hourworkdayaccordingtotheOccupational
SafetyandHealthAdministration(OSHA)is20partsper
million(ppm),16wellabovetheleveldetectablebysmell.However, the
olfactory nerves can become deadened to the
odorafterexposureof2to15minutes,dependingon concentration, so that
odor is not a reliable alarm system.
Briefly,followingaresomeofthehumanphysiological
reactionstovariousconcentrationsofH2S.Exposureto concentrations in
the range of 150 to 200 ppm for prolonged periods may cause edema
of the lungs.Nausea, stomach
distress,belching,coughing,headache,dizziness,and blistering are
signs and symptoms of poisoning in this range
ofconcentration.Pulmonarycomplications,suchas
pneumonia,arestrongpossibilitiesfromsuchsubacute
exposure.At500ppm,unconsciousnessusuallyoccurs
within30minutesandresultsinacutetoxicreactions.In the 700 to 1,000
ppm range, unconsciousness may occur in
lessthan15minutesanddeathwithin30minutes.At
concentrationsabove1,000ppm,asinglelungfulmay result in
instantaneous unconsciousness, with death quickly
followingduetocompleterespiratoryfailureandcardiac arrest.
Additional information on the toxicity of H2S can be obtained
byconsultingtheMaterialSafetyDataSheetprovidedby the manufacturer
or distributor and from consulting sources suchasDangerous
Properties of Industrial Materials by N.
IrvingSax,17DocumentationoftheThresholdLimit
Values,18andtheNIOSH/OSHAOccupationalHealth Guidelines for Chemical
Hazards.19
Fire and Explosion Hazards
H2Sisaflammablegas,yieldingpoisonoussulfurdioxide
asacombustionproduct.Inaddition,itsexplosivelimits
rangefrom4to46%inair.Appropriateprecautionsshall be taken to
prevent these hazards from developing. Experimental Considerations
Alltestsshallbeperformedinahoodwithadequate ventilation to exhaust
all the H2S.The H2S flow rates shall
bekeptlowtominimizethequantityexhausted.A10%
causticabsorbentsolutionforeffluentgascanbeusedto
furtherminimizethequantityofH2Sgasexhausted.This solution needs
periodic replenishment.Provision should be
madetopreventbackflowofthecausticsolutionintothe
testvesseliftheH2Sflowisinterrupted.Suitablesafety equipment shall
be used when working with H2S.
Particularattentionshouldbegiventotheoutputpressure
onthepressureregulatorsbecausethedownstream
pressurefrequentlyrisesascorrosionproduct,debris,and
otherobstructionsaccumulateandinterferewithregulation at low flow
rates.Gas cylinders shall be securely fastened
topreventtippingandbreakageofthecylinderhead.BecauseH2Sisinliquidforminthecylinders,the
consumptionofthecontentsshouldbemeasuredby weighing the
cylinder.The pressure gauge on the cylinder
shouldalsobecheckedfrequently,becauserelativelylittle
timeelapsesbetweenthetimethelastliquidevaporates
untilthepressuredropsfrom1,700kPa(250psi)to atmospheric
pressure.The cylinder should be replaced by the time it reaches 500
to 700 kPa (75 to 100 psi) because the regulator control may become
erratic.Flow must not be allowed to stop without closing a valve or
disconnecting the tubingatthetestvesselbecausethesolutioncontinues
to absorb H2S and move upstream into the flowline, regulator,
andeventhecylinder.Acheckvalveinthelineshould prevent the problem
if the valve works properly.However, if such an accident occurs,
the remaining H2S must be vented
asrapidlyandsafelyaspossibleandthemanufacturer notified so that the
cylinder can receive special attention.
________________________________________________________________________
Appendix B Explanatory Notes on Test Method Reasons for Reagent
Purity (see Section 2)
Waterimpuritiesofmajorconcernarealkaline-oracid-bufferingconstituentsthatwouldalterthepHofthetest
solutionandorganicandinorganiccompoundsandcould
changethenatureofthecorrosionreaction.Oxidizing
agentscouldalsoconvertpartoftheH2Stosoluble
productssuchaspolysulfidesandpolythionicacids,which may also affect
the corrosion process.
Alkalinematerials(suchasmagnesiumcarbonateand sodium silica
aluminate) are often added to (or not removed
from)commercialgradesofsodiumchloride(NaCl)to Mengfei Guo - Invoice
INV-293193-TFRMKS, downloaded on 1/7/2010 1:16:04 AM - Single-user
license only, copying and networking prohibited.TM0198-2004 NACE
International17
ensurefree-flowingcharacteristics,andthesecangreatly affect the pH.
Traceoxygenimpuritiesinthepurgegasaremuchmore
criticalifthenitrogen(orotherinertgas)iscontinuously mixed with the
H2S to obtain a lower partial pressure of H2S
inthegasandhencealowerH2Sconcentrationinthe solution.Oxidation
products could accumulate, resulting in
changesincorrosionrateand/orhydrogenentryrate(see the paragraph
below on Reasons for Exclusion of Oxygen). Test Specimen
Preparation All machining operations should be performed carefully
and slowlysothatoverheating,excessivegouging,andcold
work,etc.,donotaltercriticalphysicalpropertiesofthe
material.Uniformsurfaceconditioniscriticaltoconsistent SSR test
results. Reasons for Exclusion of Oxygen
Obtainingandmaintaininganenvironmentwithminimum
dissolvedoxygencontaminationisconsideredvery
importantbecauseofsignificanteffectsnotedinfieldand laboratory
studies. 1.OxygencontaminationinbrinescontainingH2Scan result in
drastic increases in corrosion rates by as much as
twoordersofmagnitude.Generally,theoxygencanalso
reducehydrogenevolutionandentryintothemetal.Systematicstudiesoftheparametersaffectingthese
phenomena (as they apply to SCC) have not been reported in the
literature. 2.Small amounts of oxygen or ammonium polysulfide are
sometimesaddedtoaqueousrefinerystreamsin conjunction with careful
pH control near 8 to minimize both
corrosionandhydrogenblistering.Theeffectivenessis attributed to an
alteration of the corrosion product.
Intheabsenceofsufficientdatatodefineandclarifythe
effectsofthesephenomenaonSCC,allreasonable
precautionstoexcludeoxygenshouldbetaken.The
precautionscitedinthisstandardminimizetheeffectsof oxygen with
little increase in cost, difficulty, or complexity. Cautionary
Notes Cleaningsolventssuchas1,1,1-trichloroethane,acetone,
andotherhydrocarbonliquidscanbehazardousifthe
vaporsareinhaledorabsorbedthroughtheskin.Many
chlorinatedhydrocarboncompoundsaresuspectedof being carcinogenic
and should be used only with the proper safeguards. Acid Gas
Compositions Thecompositionofgasesinequilibriumwithbrineat
elevatedtemperaturecanbedeterminedbypressure (mass) balance as
shown in Equation (B1): PT = PH2O + PH2S + PCO2(B1) Where: PT=total
absolute pressure at temperature PH2O=vapor pressure of brine
solution attemperature PH2S=partial pressure of H2S at temperature
PCO2=partial pressure of CO2 at temperature
PTshouldbedeterminedbyusingacalibratedpressure
gaugetomeasurethegaugepressureandthenadding
atmosphericpressure.PH2Oshouldbeobtainedfrom data
tables.Thepartialpressuresofacidgasesshouldbe
obtainedfromtheirmolefractions,asshowninEquations (B2) and (B3):
PH2S = (PT - PH2O) x H2S(B2) PCO2 = (PT - PH2O) x CO2(B3) where
xH2S is the mole fraction of H2S in the test gas mixture and xCO2
is the mole fraction of CO2 in the test gas mixture.
Molefractionsshouldbeobtainedfromcalibratedgas
mixturesorfromanalysisofgassamplestakenbefore and/or after testing
at ambient temperature when the vapor pressure of H2O can be
neglected. Mengfei Guo - Invoice INV-293193-TFRMKS, downloaded on
1/7/2010 1:16:04 AM - Single-user license only, copying and
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