NACE MR0175 / ISO 15156
Sour Service Materials Standard
NACE MR0175 (now also published as ISO 15156) is the international standard for materials selection in sour service (hydrogen sulphide exposure) at oil and gas production, refining, and pipeline installations. The standard codifies material qualification, hardness limits, weldment hardness control, and inspection requirements to prevent sulphide stress cracking (SSC), hydrogen-induced cracking (HIC), and stress-oriented hydrogen-induced cracking (SOHIC). Every sour-service piping and equipment item references NACE MR0175.
NACE MR0175 / ISO 15156 (Materials for use in H2S-containing environments in oil and gas production) is the foundational sour service materials standard published jointly by NACE International and ISO. The standard addresses upstream production (Part 2), pipeline transmission (Part 3), and refinery service (covered through the broader framework) for installations exposed to hydrogen sulphide above threshold partial pressures. The standard codifies material qualification (specific grades approved for sour service), hardness limits (typically 22 HRC for carbon steel, 235 HV for low-alloy steel), weldment hardness control (heat treatment requirements), and inspection methods (hardness testing per ASTM E18). See the MTR traceability software and the ASME B31.3 standard reference for the materials and piping workflow.
Sour service definition
Sour service per NACE MR0175 covers environments containing hydrogen sulphide above threshold partial pressures: 0.05 psi (0.34 kPa) for upstream production, varying for refinery and pipeline service. The hydrogen sulphide reacts with hydrogen liberated at the steel surface to cause sulphide stress cracking and hydrogen-induced cracking at sufficient hardness or stress concentrations.
Material qualification
NACE MR0175 qualifies specific material grades for sour service. Common carbon steel grades: SA-516 grade 70 with maximum 22 HRC hardness and additional HIC testing for plate. Common low-alloy steel: SA-387 grade 22 with maximum 235 HV hardness. Stainless steel options include super austenitic and duplex stainless with specific molybdenum content requirements. Each qualified grade has specific chemistry, hardness, and inspection requirements.
Weldment hardness control
NACE MR0175 requires weldment hardness control through post-weld heat treatment (PWHT) on carbon steel and low-alloy steel materials in sour service. PWHT temperature, hold time, and cooling rate per the material specification. Maximum hardness on weld metal, heat-affected zone, and base metal per the standard. Hardness testing per ASTM E18 or E10 confirms compliance.
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Upstream oil and gas production EPC projects (offshore platforms, onshore gas processing, sour gas treating) reference NACE MR0175 extensively. ONGC, Cairn India, Reliance KG Basin, and ADNOC sour service installations operate under NACE MR0175.
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Refinery sour service units (hydrotreating, hydrocracking, sulphur recovery, sour water stripping) operate piping and equipment under NACE MR0175 with periodic hardness verification.
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Indian PSU refineries operate sour service piping and equipment at refinery hydrotreating and hydrocracking units under NACE MR0175. Material certification includes MTR confirming hardness and HIC test results.
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Pipeline EPC projects for sour gas transmission reference NACE MR0175 for material selection and weldment hardness control.
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Brownfield revamp projects extending sour service piping require NACE MR0175 verification on both existing and new material. Mill test report traceability confirms hardness and HIC test results across the installation.
Pathnovo's MTR traceability software extracts mill test reports including hardness and HIC test results for NACE MR0175 sour service verification. Every delivered pipe, fitting, and valve in sour service traces back to the MTR hardness data and the project material specification. Combined with TBE automation, Pathnovo verifies vendor proposals against the NACE MR0175 material requirements.
What does NACE MR0175 cover?
NACE MR0175 (also published as ISO 15156) is the international standard for materials selection in sour service (hydrogen sulphide exposure) at oil and gas production, refining, and pipeline installations. The standard codifies material qualification, hardness limits, weldment hardness control, and inspection requirements to prevent sulphide stress cracking.
What hardness limits does NACE MR0175 specify?
Maximum hardness limits depend on material. Carbon steel: 22 HRC. Low-alloy steel: 235 HV. Stainless steel and duplex have material-specific limits with chemistry requirements (molybdenum content, etc.). Hardness limits apply to base metal, weld metal, and heat-affected zone with hardness testing per ASTM E18 or E10.
What is HIC testing?
HIC testing (Hydrogen-Induced Cracking testing per NACE TM0284) verifies plate material resistance to hydrogen-induced cracking in sour service. The test exposes a plate sample to a NACE sour environment for 96 hours and measures crack length ratio, crack thickness ratio, and crack sensitivity ratio. Required for sour service carbon steel plate above specified thickness.
What sour service applications use NACE MR0175?
Upstream oil and gas production (offshore platforms, onshore gas processing, sour gas treating), refinery sour service units (hydrotreating, hydrocracking, sulphur recovery, sour water stripping), and pipeline transmission for sour gas. Indian PSU refineries and Indian upstream operators routinely reference NACE MR0175.
Can Pathnovo verify NACE MR0175 compliance?
Yes. Pathnovo's MTR traceability software extracts mill test reports including hardness and HIC test results for NACE MR0175 sour service verification. Combined with TBE automation, the workflow validates vendor proposals against NACE MR0175 material requirements.
MTR Traceability Software
MTR hardness and HIC verification for NACE MR0175 sour service.
ASME B31.3 Standard
Process piping code that combines with NACE MR0175 for sour service.
Material Data Report Automation
Sour service equipment handover packs.
Procurement Intelligence Pillar
Full procurement workflow including sour service verification.
MTR Standard Reference
Material Test Report standard for NACE MR0175 verification.
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