Presentation on Presentation on

HYDROGEN INDUCED HYDROGEN INDUCED CRACKING CRACKING

AND AND SULFIDE STRESS SULFIDE STRESS

CRACKINGCRACKINGbyby DENZIL D’ SOUZADENZIL D’ SOUZA

Contents

What is HIC/SSC ? How it occurs? Where is occurs? Standards used by ARAMCO Test Method to check HIC resistance

steel Acceptance criteria

What is HICWhat is HIC

HIC is internal cracks caused in material by HIC is internal cracks caused in material by trapped nascent hydrogen atoms.trapped nascent hydrogen atoms.

Atomic hydrogenAtomic hydrogen, and not the molecule, is the , and not the molecule, is the smallest atom and it is small enough to diffuse smallest atom and it is small enough to diffuse readily through a metallic structure. When the readily through a metallic structure. When the crystal lattice is in contact or is saturated with crystal lattice is in contact or is saturated with atomic hydrogen, the mechanical properties of atomic hydrogen, the mechanical properties of many metals and alloys are diminished many metals and alloys are diminished

2H2H(atoms)(atoms) H H2 (gas)2 (gas)

If the formation of molecular hydrogen is suppressed, If the formation of molecular hydrogen is suppressed, the nascent atomic hydrogen atom can diffuse into the the nascent atomic hydrogen atom can diffuse into the interstices of the metal instead of being harmlessly interstices of the metal instead of being harmlessly evolved as a gaseous reaction product thus producing evolved as a gaseous reaction product thus producing a crack in the material.a crack in the material.

Residual and applied tensile stress not necessary for Residual and applied tensile stress not necessary for HICHIC

Certain chemical species poison this recombination Certain chemical species poison this recombination (e.g. cyanides, arsenic, antimony, or selenium (e.g. cyanides, arsenic, antimony, or selenium compounds). However, the most commonly compounds). However, the most commonly encountered species is hydrogen sulfide (H2S), encountered species is hydrogen sulfide (H2S), formed in many petrochemical process.formed in many petrochemical process.

Sources of hydrogen Sources of hydrogen

In the making of steelIn the making of steelIn processing parts, In processing parts, In welding, In welding, In storage or containment of hydrogen gas,In storage or containment of hydrogen gas,Hydrogen as a contaminant in the environment having Hydrogen as a contaminant in the environment having low low

ph that is often a by-product of general corrosion ph that is often a by-product of general corrosion

Hydrogen embrittlement:Hydrogen embrittlement:

IIngress of hydrogen into a component causing brittle failures at stresses ngress of hydrogen into a component causing brittle failures at stresses below the yield stress of susceptible materials.below the yield stress of susceptible materials.

Methane formationMethane formation

Reduce ductilityReduce ductility

Reduce load bearing CapacityReduce load bearing Capacity

Crack formationCrack formation

Failure below Yield stress by brittle FractureFailure below Yield stress by brittle Fracture

HIC IN WELDING HIC IN WELDING Cold cracking/ HAZ cracking Cold cracking/ HAZ cracking

Source for Hydrogen entrapmentSource for Hydrogen entrapment

MoistureMoisture

Organic CompoundsOrganic Compounds

Occurs 72 hrs later of weldingOccurs 72 hrs later of welding At 450 F H diffuse at rate of 1 inch /hrAt 450 F H diffuse at rate of 1 inch /hr At 220 1 inch / 48 hrAt 220 1 inch / 48 hr Room temp 2 weeksRoom temp 2 weeks PreventionPrevention

Weld surface should free of moistureWeld surface should free of moisture PWHT 400-450 F holding for 1 hr. will redistribute PWHT 400-450 F holding for 1 hr. will redistribute

the H thru diffusion. thus reducing risk of H the H thru diffusion. thus reducing risk of H crackingcracking

Hydrogen Blistering Hydrogen Blistering

Nucleation of Hydrogen gas at internal defectsNucleation of Hydrogen gas at internal defects

Rupture of materialRupture of material

What is sour service ?What is sour service ?Sour service is a environment containing water and Sour service is a environment containing water and HH22S( hydrogen sulfide) with pressure of 50PPMS( hydrogen sulfide) with pressure of 50PPM

If the presence of hydrogen sulfide i.e. sour services If the presence of hydrogen sulfide i.e. sour services causes entry of hydrogen into the component, the causes entry of hydrogen into the component, the cracking phenomenon is often termed “Sulfide Stress cracking phenomenon is often termed “Sulfide Stress cracking (SSC)”cracking (SSC)”

Electrochemical corrosion reactionsElectrochemical corrosion reactions produce H atoms

Chemical ReactionsChemical Reactions H2S(aq) + H2O(l)  H3OH2S(aq) + H2O(l)  H3O++(aq) + HS(aq) + HS--(aq) ((aq) (BisulfideBisulfide) )

--------1--------1

H2O(l) + H2O(l)   H3OH2O(l) + H2O(l)   H3O++(aq) + OH(aq) + OH--(aq)  (aq)  -----------------------2-----------------------2

HSHS--(aq) + H(aq) + H22O(l) <==> HO(l) <==> H22S(aq) + OHS(aq) + OH--(aq) (aq)

SS2-2-(aq)( (aq)( SulfideSulfide) + H) + H22O(l) <==> HSO(l) <==> HS--(aq) + OH(aq) + OH--(aq) (aq) --------3--------3

The sulfide ion then combines with ferrous ions to form The sulfide ion then combines with ferrous ions to form iron sulfide. The metal surface is dissolved.iron sulfide. The metal surface is dissolved.

How are H atoms ions produced ?How are H atoms ions produced ?

Factors influencing SSCFactors influencing SSC

Increase in acidity ( low pH)Increase in acidity ( low pH) Carbon DioxideCarbon Dioxide Increased stressIncreased stress Ambient Temperature (-7 to 49 degree Ambient Temperature (-7 to 49 degree

C)C)

Medium strength steel are more susceptible for HICMedium strength steel are more susceptible for HIC

The most vulnerable are high-strength steels, titanium The most vulnerable are high-strength steels, titanium alloys and aluminum alloys. alloys and aluminum alloys.

a. Blistera. Blisterb. HICb. HICc. SSC (low strength steel)c. SSC (low strength steel)d. (high strength steel)d. (high strength steel)

Non BranchingNon Branching Fast GrowingFast Growing

Standards usedStandards used SAES-A-301 ( Materials Resistant to Sulfide Stress SAES-A-301 ( Materials Resistant to Sulfide Stress

Corrosion Cracking ) Corrosion Cracking ) replaced now replaced now

ISO 15156-2003 Petroleum and natural gas industries ISO 15156-2003 Petroleum and natural gas industries – Materials for use in H– Materials for use in H22S containing environments in S containing environments in oil and gas production.oil and gas production.

It gives requirements and recommendations for the selection It gives requirements and recommendations for the selection carbon and low alloy steels for service in equipment, used in oil carbon and low alloy steels for service in equipment, used in oil and natural gas production and natural gas treatment plants in Hand natural gas production and natural gas treatment plants in H22S S containing environmentscontaining environments

This addresses the resistance of the steel to damage that may be This addresses the resistance of the steel to damage that may be caused by SSC and HICcaused by SSC and HIC

01-SAMSS-016 - 01-SAMSS-016 - Qualification of Pipeline, In plant Qualification of Pipeline, In plant Piping and pressure Vessel Steels for Resistance to Piping and pressure Vessel Steels for Resistance to Hydrogen –Induced CrackingHydrogen –Induced Cracking

SCOPESCOPE

This specification is supplementary to current NACE This specification is supplementary to current NACE TM0284 (Evaluation of pipeline and pressure vessel steels TM0284 (Evaluation of pipeline and pressure vessel steels for resistance of hydrogen induced cracking)for resistance of hydrogen induced cracking)

Not Applicable to seamless pipeNot Applicable to seamless pipe

Applicable for following steel productsApplicable for following steel products

High Frequency welded pipeline per 01-SAMSS-332High Frequency welded pipeline per 01-SAMSS-332

Or / 01-SAMSS-333Or / 01-SAMSS-333

Submerged arc welded pipeline 01-SAMSS-035 and 01-SAMSS-Submerged arc welded pipeline 01-SAMSS-035 and 01-SAMSS-038038

Pressure Vessel Plate per 32-SAMSS-004Pressure Vessel Plate per 32-SAMSS-004

Mandatory requirementsMandatory requirements The steel manufacturer shall guarantee that the pipe

fabrication cold forming processes will not compromise the HIC resistance of the strip/plate.

Pseudo-HIC Resistant steel shall not be used to fabricate equipment intended for sour service application. Steel that passes the HIC test, but has not been initially manufactured to be HIC resistant steel shall not be used.Pseudo-HIC Resistant Steel : Plate/Strip that is not fabricated utilizing the quality control/assurance and fabrication measures to intentionally produce HIC resistant steel.

Form 175-010200 - Inspection and testing requirements - HIC Testing

Appendix B-Test Procedure for Appendix B-Test Procedure for Evaluating HIC in HEvaluating HIC in H22S Saturated S Saturated

Solution ASolution A This test procedure is described in NACE TM0284-2003This test procedure is described in NACE TM0284-2003

Solution A-Solution A- A sodium chloride, acetic acid (NaCl, A sodium chloride, acetic acid (NaCl, CH3COOH) solution saturated with HCH3COOH) solution saturated with H22S at ambient S at ambient temperature and pressuretemperature and pressure

Solution B-Solution B- A synthetic seawater solution saturated with H2S A synthetic seawater solution saturated with H2S at ambient temperature and pressure at ambient temperature and pressure

As per As per 01 –SAMSS-01601 –SAMSS-016 test solution shall be Solution A test solution shall be Solution A

ApparatusApparatus

ProcedureProcedure Each test specimen shall be 100 ±1 mm long by

20 ±1 mm wide.

The test specimen thickness shall be the full wallthickness of the pipe up to a maximum of 30 mm.

3 test specimens shall be taken from eachtest pipe for pipes produced by continuous casting and 6 for ingot casting

3

Sample 1

Sample 2

Sample 3

Plate Rolling Direction

Plate Thickness 30<T<89mm

Plate Thickness T>88mm

pH of solution A : 2.7 ± 0.1

Concentration of H2S measured by iodometric titration, shall be min of 2300ppm

Test duration :96 hrs

Temperature :25 ± 3 °C

Evaluation of Test Specimens Specimen shall be Sectioned Each section shall be polished metallographically and etched All faces to be examined shall be subjected to either wet magnetic particle

testing or macro etching prior to final metallographic polishing Cracks shall be measured as illustrated in Figure

Definitions:

The "Crack Length Ratio"(CLR) is defined as the sum of the lengths of the individual longitudinal cracks divided by the width of the polished specimen face times 100%

CLR =( Σ a ∕ W ) x 100 %

The "Crack Thickness Ratio" (CTR) is defined as the sum of the thickness of crack arrays divided by the thickness of the polished specimen face times 100%

CTR =( Σ b ∕ T ) x 100 %

Reporting Test ResultsReporting Test Results The CLR and CTR results of the control sample shall be reported.

Longitudinal crack – Avg CLR <10%Transverse crack – Avg CTR < 3%

pH of H2S saturated solution before addition of H2s,at the start and end of the test.

Chemical composition of material tested, including Al, B, C, Ca, Cr, Cu, Mn, Mo, Ni, Nb, N, P, Si, S, Ti and V.

Results of cracking evaluation.

Photomicrographs of metallographically -polished (1 micron finish) specimens Magnifications 100x to 500x

Hardness shall not exceed 250 HV. (load 5-10 kg)

THE ENDTHE END

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