NACE MR0175 / ISO 15156 — H₂S Sour Service

Sour Service Materials Supplier Saudi Arabia — NACE MR0175 / ISO 15156

Gulf Union Ozone stocks NACE MR0175 and ISO 15156 compliant valves, pipe fittings, flanges, and piping for H₂S sour service in Saudi Aramco and EPC projects. Our inventory includes HIC-tested API 5L PSL2 carbon steel pipe, duplex stainless steel 2205, and austenitic 316L — the three material families most specified for Saudi oilfield sour service conditions. EN 10204 3.1 MTCs standard; 3.2 with TPI witness on request.

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NACE MR0175 sour service materials — valves, pipe fittings and flanges for Saudi Aramco H₂S projects
Definition

What Is Sour Service? The H₂S Threshold

A fluid is classified as "sour" when it contains hydrogen sulphide (H₂S) at a concentration above the threshold defined by NACE MR0175 / ISO 15156. The threshold is an H₂S partial pressure of 0.3 kPa (0.05 psia) in the gas phase. Above this level, the risk of H₂S-related material degradation is considered significant enough to require specifically qualified materials.

Saudi Arabia's oilfields — particularly in the Eastern Province (Ghawar, Safaniya, Shaybah) — produce crude oil and associated gas with H₂S concentrations that routinely exceed this threshold. Saudi Aramco's SAES-L-133 governs sour service piping design across all Aramco facilities, mandating specific material grades, hardness limits, welding requirements, and post weld heat treatment (PWHT).

The consequences of using a non-sour-qualified material in an H₂S environment can be catastrophic and rapid: a carbon steel pipe with hardness above 22 HRC can fail by sulfide stress cracking (SSC) within hours of exposure. Correct material specification at procurement stage is the primary safeguard.

Sour Service Threshold

NACE MR0175 / ISO 15156: H₂S partial pressure ≥ 0.3 kPa (0.05 psia) triggers sour service material requirements.

Aqueous phase: If free water is present at any H₂S concentration, NACE MR0175 applies — even if the partial pressure is below 0.3 kPa — because the aqueous phase can concentrate H₂S locally at the steel surface.

22
HRC max hardness (CS)
3.2
EN 10204 type (critical sour)
Failure Mechanisms

H₂S Failure Mechanisms: SSC, HIC & SOHIC

Understanding the failure mechanism determines which test and which material grade to specify. Not all H₂S failures are the same:

SSC
Sulfide Stress Cracking

Occurs when a susceptible (high-hardness) material is under tensile stress — applied or residual — in an H₂S-containing aqueous environment. Atomic hydrogen enters the steel and embrittles it; cracks initiate at stress concentrations and propagate. Strongest driver: hardness. NACE MR0175 sets the primary hardness limit at ≤22 HRC (≈250 HBW) for carbon and low-alloy steels.

Test: NACE TM0177 (SSC)
HIC
Hydrogen Induced Cracking

Occurs in carbon steel pipe even without applied stress. Hydrogen atoms produced at the steel surface by the corrosion reaction in wet H₂S diffuse into the metal and collect at internal laminar inclusions (manganese sulphide stringers). They recombine into H₂ molecules, building up pressure until internal cracks form parallel to the rolling direction. Mandated by SAES-L-133 for all CS pipe in Aramco sour service. Prevented by clean steel chemistry (low S, low P, low CE) and normalising heat treatment.

Test: NACE TM0284 (HIC) — required by SAES-L-133
SOHIC
Stress-Oriented HIC

A combination of HIC and applied/residual stress that causes the HIC steps to link up through the steel thickness, creating a through-crack perpendicular to the stress direction. Particularly dangerous in weld heat-affected zones (HAZ) of pressure vessel shells and pipe seam welds. Mitigated by PWHT, low heat input welding, and use of HIC-resistant base metals per SAES-A-206 / SAES-L-133.

Mitigated by: PWHT + HIC-tested base metal
Material Selection

Sour Service Material Selection Guide — Saudi Aramco Projects

Material selection for sour service is governed by H₂S concentration, temperature, chloride content, pH, and service pressure. The table below covers the most common specifications for valves, pipe fittings, flanges, and piping in Saudi Aramco sour service applications:

Material Family Grade / Spec NACE MR0175 Qualified? Typical Sour Service Use Key Requirement
Carbon Steel API 5L PSL2 (Gr. B, X42, X52, X60) Yes — with HIC testing Sour service pipelines, gathering systems HIC tested per NACE TM0284; CE ≤0.43; hardness ≤22 HRC
ASTM A234 WPB / ASTM A105 Yes — hardness controlled Butt-weld fittings, flanges in sour service Hardness ≤22 HRC; PWHT of welds per SAES-L-133
Austenitic Stainless Steel ASTM A182 F316L / ASTM A312 TP316L Yes — annealed condition Valves, fittings, flanges in wet H₂S service Must be solution annealed; hardness ≤22 HRC; no cold work
ASTM A182 F304L / ASTM A312 TP304L Yes — annealed condition General utility sour service; lower chloride environments Solution annealed; avoid high chloride environments (SCC risk)
Duplex Stainless Steel 2205 — UNS S31803 / S32205
ASTM A182 F51 / A790 / A928		 Yes — solution annealed Sour service pipe, fittings, valves in high-chloride / elevated temperature Hardness ≤28 HRC; ferrite content 35–65%; solution annealed + quenched
Super Duplex Stainless Steel 2507 — UNS S32750
ASTM A182 F53 / A790		 Yes — solution annealed Severe sour service, offshore, high-chloride process streams PREN ≥40; hardness ≤32 HRC; microstructure verification required
Aramco Requirements

SAES-L-133: Saudi Aramco Sour Service Piping Requirements

SAES-L-133 is Saudi Aramco Engineering Standard governing the design and material requirements for piping systems in sour service. It supplements NACE MR0175 / ISO 15156 with Aramco-specific requirements that are often more stringent than the base NACE standard.

Key SAES-L-133 requirements for contractors and material suppliers:

≤15%
CLR limit
Crack Length Ratio
≤5%
CTR limit
Crack Thickness Ratio
≤2%
CSR limit
Crack Sensitivity Ratio
Carbon Steel Pipe — HIC Testing Mandatory

All carbon steel pipe in Aramco sour service must be HIC-tested per NACE TM0284. Test results must show Crack Length Ratio (CLR) ≤15%, Crack Thickness Ratio (CTR) ≤5%, and Crack Sensitivity Ratio (CSR) ≤2%. This is a PSL2 supplementary requirement — standard API 5L PSL1 pipe does not qualify.

Hardness Limits — All Materials

Base metal, weld metal, and heat-affected zone (HAZ) hardness must not exceed 22 HRC (237 HBW) for carbon and low-alloy steels. Hardness testing must be documented in the MTC. SAES-L-133 requires 100% HAZ hardness verification on sour service piping welds.

PWHT — Mandatory for CS Welds

Post Weld Heat Treatment is mandatory for all carbon steel welds in sour service piping under SAES-L-133, regardless of wall thickness. PWHT reduces residual stress and lowers HAZ hardness, both of which mitigate SSC. Stress relief at 620–650°C is the standard treatment range.

EN 10204 3.2 — For Critical Sour Service

For safety-critical sour service materials, SAES-L-133 and individual POs often specify EN 10204 Type 3.2 inspection certificates — requiring a third-party inspector to witness and countersign the mill test results. Gulf Union Ozone can coordinate TPI witness inspection at the mill for 3.2 orders.

GUO Sour Service Stock
✓
API 5L PSL2 HIC-tested pipe
Gr. B, X42, X52 — NACE TM0284 HIC results available
✓
ASTM A182 F316L valves, fittings & flanges
Solution annealed, hardness ≤22 HRC documented in MTC
✓
Duplex 2205 — ASTM A182 F51 / A790
Pipe, fittings, and flanges for high-chloride sour service
✓
EN 10204 3.1 standard; 3.2 with TPI on request
Coordinate at order stage to avoid lead-time delay
✓
PMI testing on alloy and SS materials
Positive Material Identification per SAEP-1142 on request
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Related Resources

Further Reading

Product Page
Duplex & Super Duplex Stainless Steel
2205 and 2507 pipe, fittings and flanges for high-chloride and sour service applications.
Comparison Guide
API 5L vs ASTM A106 Grade B
PSL1 vs PSL2 explained — including the HIC-test supplementary requirement for sour service.
Explainer
EN 10204 3.1 vs 3.2 Guide
When Aramco requires 3.2 with TPI witness inspection — and how to coordinate it without delaying delivery.
Procurement Guide
Industrial Parts Supplier Saudi Arabia: B2B Procurement Guide
Complete sourcing guide for Aramco and EPC contractors in Saudi Arabia.
Valve Spec
NACE MR0175 Sour Service Valves — 22 HRC Certified
API 600 gate, API 6D ball, check, and globe valves for H₂S sour service — hardness certified, SAEP-347 Annex 3, Jeddah stock.
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Send your material specification, size, pressure class, quantity, and whether EN 10204 3.1 or 3.2 is required. We confirm stock and documentation availability and respond within 4 business hours.

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In Summary

Gulf Union Ozone Trading Co. supplies Sour Service Materials to industrial customers across Saudi Arabia with delivery from our Jeddah warehouse — all products ship with original Mill Test Certificates and Certificates of Conformance.

In Summary

Sour Service Materials from Gulf Union Ozone serves Saudi Aramco SAEP-347 projects, SABIC, SADARA, SEC utilities, NEOM mega-projects, and industrial facilities across the Kingdom — our inventory covers the most common material grades and pressure ratings.

In Summary

Gulf Union Ozone stocks a wide range of Sour Service Materials including various grades, sizes, and pressure classes — contact us on WhatsApp for immediate availability confirmation and a quotation with full MTC documentation.

In Summary

For urgent Sour Service Materials procurement in Saudi Arabia, WhatsApp +966 55 098 8062 — our procurement team confirms stock availability within the hour and provides competitive quotations with full compliance documentation for Aramco, SABIC, SEC, and government projects.