NACE MR0175
/glossary/nace-mr0175AMPP / ISO materials-selection standard for metallic equipment in H2S oil and gas production.
NACE MR0175 / ISO 15156 is the materials-selection document for H2S-containing oil and gas production. Kanpur is an indent point for API 5L line pipe that later sits on a gathering line or well-pad in Uttar Pradesh or Bihar. ISO 15156-1:2020 names seven H2S cracking mechanisms and says the standard supplements, not replaces, the design code. Write the H2S envelope and the base pipe spec on the same RFQ.
In detail
NACE MR0175 is published with ISO 15156. ISO 15156-1:2020 sets general principles for metallic materials in H2S-containing oil and gas production and natural-gas sweetening plants. It supplements design codes and addresses cracking: sulfide stress cracking, stress corrosion cracking, hydrogen-induced cracking, stepwise cracking, SOHIC, soft-zone cracking, and galvanically induced hydrogen stress cracking. Part 2 covers carbon and low-alloy steels and cast irons. Part 3 covers corrosion-resistant alloys. PSL2 or a 22 HRC stamp does not qualify a pipe for every sour envelope.
What MR0175 is, and what it is not
ANSI/NACE MR0175 / ISO 15156 is one document family published by AMPP and ISO. The ISO 15156-1:2020 catalogue page titles Part 1 General principles for selection of cracking-resistant materials. The abstract covers metallic materials in oil and gas production and in natural-gas sweetening plants where H2S is present and a failure can harm people or the environment.
Part 1 states that the document supplements, but does not replace, the materials requirements in the design code, standard, or regulation. It addresses sulfide stress cracking, stress corrosion cracking, hydrogen-induced cracking and stepwise cracking, stress-oriented hydrogen-induced cracking, soft-zone cracking, and galvanically induced hydrogen stress cracking. It applies to load-controlled design. Strain-based design is sent to Clause 5.
ISO 15156-2:2020 covers cracking-resistant carbon and low-alloy steels and the use of cast irons. It addresses SSC, SOHIC, SZC, HIC, and possible stepwise cracking. It is concerned only with cracking. Mass-loss and localized corrosion sit outside that part. Annex A lists SSC-resistant carbon and low-alloy steels.
ISO 15156-3:2020 covers cracking-resistant CRAs and other alloys. It addresses SSC, SCC, and GHSC. The Part 3 abstract says the document is not necessarily suitable for refining or downstream equipment. A refinery process line in Panki is not sour-qualified because someone typed NACE on the RFQ.
MR0175 is not a pipe dimensional standard. It does not set NB, schedule, or bevel. It is not IS 1239, not IS 3589, and not SA210. It is not a hardness conversion chart that turns every carbon steel into 22 HRC.
Who must apply MR0175, and who should leave it off
The operator and the materials engineer decide whether the production environment is sour and which ISO 15156 part and table apply. An EPC buying API 5L or ASTM A106 from Kanpur for a well-fluid or gathering line must attach that environment: H2S partial pressure, in-situ pH, chloride, and temperature.
Use Part 2 when the approved route is carbon or low-alloy steel. Use Part 3 when the approved route is a CRA. Downhole L80, C90, T95, and P110 have their own restricted-yield chemistry and hardness routes on the site NACE page; copy the grade the completion design names.
Leave MR0175 off a Kanpur PWD or JJM water main, a fire hydrant, a borewell casing PO, and a sugar-mill boiler-tube indent. Those duties use IS 1239, IS 3589, IS 4270, or SA192 / SA210. Adding NACE without an H2S envelope delays the quote and does not make the lot sour-qualified.
Do not treat PSL2 as a sour certificate. API's 46th-edition announcement names PSL 2 pipe for sour service as a key change, which means sour is a stated option, not the default. Do not treat a 250 HV10 or 22 HRC stamp as universal. The site NACE page is explicit: that pair is one carbon-and-low-alloy screening point, not every table.
Parts and material families for a Kanpur sour RFQ
The table restates the site NACE checklist so an indent from Kanpur can be compared on one sheet. Evidence is a document, not a logo. Part titles are cited from the ISO 15156:2020 catalogue; that edition year is the reference, not a separate as-of date.
| Part | Material family | Cracking in scope | Evidence the buyer files |
|---|---|---|---|
| ISO 15156-1:2020 | All metallic equipment in scope | SSC, SCC, HIC/SWC, SOHIC, SZC, GHSC | Defined environment plus selected route |
| ISO 15156-2:2020 | Carbon and low-alloy steel, cast iron | SSC, SOHIC, SZC, HIC/SWC | Part 2 table or qualification, hardness records |
| ISO 15156-3:2020 | CRAs and other alloys | SSC, SCC, GHSC | Exact alloy, condition, Part 3 route |
| API 5L (base product) | Line pipe, PSL1 or PSL2 | Product tests only | MPS plus sour wording if the project invokes it |
| NACE TM0177 | Laboratory SSC / SCC test | Test method, not a pipe spec | Project-named method A/B/C/D report |
Two offers that both say NACE are not comparable if they qualified different H2S regions or different heat-treatment conditions. Resolve the envelope before you compare rupees per kg.
How to specify sour-service pipe on an RFQ
Order a base product first, then the ISO 15156 supplement. A line that says only NACE pipe will attract welded water tube, A106, and API 5L in the same inbox.
- Base standard and grade: API 5L PSL1 or PSL2 with the X-grade, or ASTM A106 Grade B, copied from the drawing.
- Size: NPS or OD, wall or schedule. End finish: plain or bevel.
- Environment: H2S partial pressure in kPa or psi, in-situ pH, chloride, operating temperature.
- ISO 15156 part, table or qualification route, and environmental region 0-3.
- Condition: heat treatment, permitted cold work, weld state, and PWHT if the route requires it.
- Hardness: method (HV10, HRC, HBW), locations (parent, weld, HAZ), and the table limit.
- SSC test: NACE TM0177 method when the operator requires laboratory qualification.
- Documents: EN 10204 3.1 or 3.2 MTC, heat identity, hardness map, qualification record. TPI by SGS, Bureau Veritas, Lloyds, or TUV when the ITP names the agency.
- Delivery: ex-warehouse Kanpur. GST 18% extra. Quantity in metres and MT.
Worked mass check for a 6 inch gathering-line take-off
Steel mass does not prove sour qualification. Use the site formula once to size the truck: W = (OD − t) × t × 0.02466 kg/m.
The pipe schedule chart gives 6 inch NPS (DN 150) as OD 168.3 mm and Sch 40 wall 7.11 mm. W = (168.3 − 7.11) × 7.11 × 0.02466 = 161.19 × 7.11 × 0.02466 = 28.26 kg/m. A 6 m pipe is 169.6 kg before coating.
The seamless price list band for 6 inch NPS Sch 40 is ₹75-92 per kg ex-warehouse Kanpur as of 24 May 2026. That 6 m length is 169.6 × 75 = ₹12,720 to 169.6 × 92 = ₹15,603 before GST, freight, coating, and any sour-test line. Do not treat that carbon band as a qualified ISO 15156 lot.
Pressure rating still needs size, wall, allowable stress, and the design code. Sour hardness and HIC tests add mass to the document pack, not to the 28.26 kg/m steel figure.
Common mistakes on sour-service orders
In practice, the first failure is writing NACE on an IS 1239 or SA210 RFQ that never sees well fluid. The mill then prices a hardness stamp the water inspector does not need.
The second failure is treating API 5L PSL2 as sour by default. The 46th-edition announcement treats sour-service PSL 2 as a named option. Write the environment and the ISO 15156 route, or leave sour off.
The third failure is a hardness number with no method and no location. 22 HRC on the OD is not 250 HV10 in the HAZ. Copy the table, the scale, and the map.
The fourth failure is cold bending or field welding after a Part 2 qualification that limited deformation. The approved condition includes the weld and the bend. Requalify or heat-treat as that route requires.
The fifth failure is a generic NACE sentence on the MTC with no link to heat, table, or environment. File the qualification record with the same heat number that is stenciled on the pipe.
Standards and compliance for sour service
Cite ISO 15156-1:2020, ISO 15156-2:2020, and ISO 15156-3:2020 by those catalogue titles. The identical AMPP publication is ANSI/NACE MR0175-2021/ISO 15156:2020. Technical circulars and errata sit on top of that edition; the operator names the circulars that apply.
NACE TM0177 is the laboratory method for SSC and SCC in H2S. A secondary TWI explainer summarises Method A tensile, Method B bent-beam, Method C C-ring, and Method D double-cantilever beam. TM0177 sets the procedure. It does not set pass-fail for a pipeline. The project does.
API Specification 5L remains the line-pipe product standard. ISO 3183 is the ISO counterpart named on the site API page. ASTM A106/A106M-26 remains the seamless carbon pipe product standard for high-temperature service in NPS 1/8 to NPS 48.
If the same joint later sits inside an Indian boiler boundary, classify the component. Form III-A is the IBR certificate for steam pipes, Form III-B for tubes, and Form III-C for boiler mountings and fittings. A sour MTC does not replace those forms.
Sour-service pipe from a Kanpur indent
Kanpur is not an oilfield. The yard at 83/124 Bartan Bazar, Basanti Nagar (208014) is where a North India EPC collects or stages API 5L and A106 before the truck runs to a well site or a compressor station. Intra-city fabricators in Panki, about 12 km away, sometimes cut and bevel that pipe. They do not invent the H2S envelope.
Offers leave ex-warehouse Kanpur. The FAQ service area is Uttar Pradesh, Bihar, Madhya Pradesh, Delhi NCR, and Uttarakhand. Patna and Lucknow are the two city pages most sour-indent buyers already use for delivery language.
See NACE MR0175 on the standards hub, API 5L, seamless pipes in Kanpur, and the seamless pipe price list. PWD and JJM buyers should stay on those water pages. A hardness stamp will not pass a Jal Nigam hydrotest ITP.
Mill-direct alloy on the lead-time entry is 21-30 days for SA213 T11/T22. Sour line pipe is its own mill slot. Ask the offer to print the ready date for that NPS and the TPI hold point. RP Sales replies to the RFQ within 4 working hours.
Hardness, welds, and TM0177
Some carbon- and low-alloy-steel routes on the site NACE page use 250 HV10 or 22 HRC. Read that pair from the applicable Part 2 table and condition. Do not convert HRC to HV on the back of the challan and call it compliance.
Welds need a procedure, a heat-treatment condition, and hardness locations that the selected route names. Parent-metal HRC on the stencil does not cover the HAZ. Name SGS, Bureau Veritas, Lloyds, or TUV only when the ITP wants that witness.
Cold work can push a previously listed steel out of its table. The Part 2 route states the permitted deformation and any requalification. A field cold bend on a Kanpur-supplied joint is a new condition.
When the operator wants laboratory SSC evidence, name NACE TM0177 and the method (A, B, C, or D). File the lab report with the heat number. A mill logo that says NACE is not Method A.
API 5L PSL2 versus a sour route
PSL2 adds chemistry, toughness, and NDE relative to PSL1. It does not, by itself, place the pipe in an ISO 15156 table. Write PSL2 when the project wants PSL2. Write the sour route when the project wants sour.
The API 5L 46th-edition announcement retrieved on this site updates hardness testing on PSL 2 pipe for sour and offshore service. That sentence is why a buyer must say sour, not hope the mill guessed.
Coating, bevel, and jointer rules stay on the API 5L line. Cement-mortar or 3LPE on an IS 3589 water main is a different family. Do not mix those coating sentences onto a sour indent.
Compare two Kanpur offers only after base grade, PSL, environment, ISO part, hardness method, and document list match. Then the rupee-per-kg line means something.
Documents that travel with a sour bundle
An MTC already travels with each RP Sales load. For sour, add the qualification record, the hardness map, and the TM0177 report when the RFQ asked for them. Heat numbers on the stencil, the MTC, and the challan must match.
EN 10204 Type 3.1 is manufacturer QC. Type 3.2 is countersigned. Sour EPCs often want 3.2 plus TPI. Name the agency on the RFQ so the hold point is booked before the mill rolls.
The dispatch challan should list NPS, wall, grade, PSL, heat, and "ISO 15156-2" or "ISO 15156-3" as written on the PO. A challan that says only NACE pipe is how the site storekeeper receives the wrong family.
Keep Form III-B and Form III-C off this pack unless a boiler component is actually on the same truck. Sour line pipe is not a boiler mounting.
Where you'll meet this in procurement
You will meet NACE MR0175 when a buyer, consultant, or mill quote names a governing specification. Confirm which revision applies, what tests the standard requires, and whether the grade on the MTC actually matches the NACE MR0175 call-out on the RFQ before you lock commercial terms.
Related terms
Related resources
Key points
- ISO 15156-1:2020 supplements the design code and names seven H2S cracking mechanisms. It does not replace API 5L or A106 dimensions.
- Part 2 is carbon and low-alloy steel. Part 3 is CRAs. Part 3 is not written for refining or downstream equipment.
- 250 HV10 / 22 HRC is one carbon-and-low-alloy screening pair on the site NACE page, not a universal limit.
- PSL2 is not a sour certificate. Write the H2S envelope, the ISO table, and the hardness method.
- A 6 inch Sch 40 take-off is 28.26 kg/m from (168.3 − 7.11) × 7.11 × 0.02466. Sour indents from Kanpur still budget GST 18% extra on the steel line.
Frequently asked questions
Sources
- ISO 15156-1:2020. Petroleum and natural gas industries: Materials for use in H2S-containing environments in oil and gas production: Part 1: General principles for selection of cracking-resistant materials (International Organization for Standardization)
- ISO 15156-2:2020. Part 2: Cracking-resistant carbon and low-alloy steels, and the use of cast irons (SSC, SOHIC, SZC, HIC/SWC; Annex A) (International Organization for Standardization)
- ISO 15156-3:2020. Part 3: Cracking-resistant CRAs (corrosion-resistant alloys) and other alloys (SSC, SCC, GHSC) (International Organization for Standardization)
- NACE TM0177-2016. Laboratory Testing of Metals for Resistance to Sulfide Stress Cracking and Stress Corrosion Cracking in H2S Environments (Methods A, B, C, D) (AMPP)
- TWI Job Knowledge (secondary explainer). NACE TM0177 sour test methods: plain-language summary of Methods A-D, not the standard itself (TWI Ltd)
- API Specification 5L: 46th Edition (announcement). Publication of the 46th edition of Specification 5L, Line Pipe: PSL 2 sour-service and offshore hardness updates (American Petroleum Institute)
- ASTM A106/A106M-26. Standard Specification for Seamless Carbon Steel Pipe for High-Temperature Service (NPS 1/8 to NPS 48) (ASTM International)
- Indian Boiler Regulations, 1950. Forms index: III-A steam pipes, III-B tubes, III-C boiler mountings and fittings (Central Boilers Board, Government of India)