Which other standards appear next to NACE MR0175 in valve tenders?

Sour-service requirements usually sit beside a valve product standard such as API 6D or ASME B16.34, and a certificate requirement such as EN 10204. Fugitive emission rules such as ISO 15848-1 often appear too. Read them together, because sour service can limit the seal and trim options you offer.

Standards explainer

NACE MR0175 / ISO 15156: what sour service means for your tender offer

A plain-English overview of the sour-service materials standard for bid engineers at valve, pump and actuator makers, with a checklist for datasheets and certificates.

By Ademola Afolabi, Founder, New Odyssey Ltd · Last reviewed: 2026-10-23

The short answer

NACE MR0175 / ISO 15156 sets requirements for metallic materials in oil and gas production equipment exposed to H2S. It aims to prevent cracking such as sulfide stress cracking. In a tender, check every wetted and exposed part, its hardness and condition, and the certificates the buyer wants.

Key Takeaways

ISO 15156 has three parts: general principles, carbon and low-alloy steels, and corrosion-resistant and other alloys.
The purchaser should define the service conditions; the manufacturer selects materials that meet the limits for them.
MR0175 is for oil and gas production; NACE MR0103 / ISO 17945 is for refining.
A bare NACE compliant note on a datasheet rarely satisfies a buyer: name the edition, parts and exceptions.

What NACE MR0175 / ISO 15156 covers

NACE MR0175 / ISO 15156 is published jointly by ISO and NACE, now part of AMPP. It covers metallic materials for equipment used in oil and gas production and processing where H2S is present. Its purpose is to prevent cracking caused by H2S, such as sulfide stress cracking, rather than general corrosion. It sets out how to select and qualify materials, and lists the environmental, hardness and heat-treatment limits for common material groups.

The three parts of ISO 15156 (own summary)
Part	What it covers in outline
Part 1	General principles for selecting cracking-resistant materials, and how to qualify a material by testing or field experience
Part 2	Cracking-resistant carbon and low-alloy steels, and the use of cast irons
Part 3	Cracking-resistant corrosion-resistant alloys (such as stainless steels and nickel alloys) and other alloys

MR0175 or MR0103: production or refining?

MR0175 / ISO 15156 is written for oil and gas production. Sour refining environments have their own standard, NACE MR0103, with an ISO counterpart, ISO 17945. The two have different scopes and material rules. If a refinery tender cites MR0175, or a production tender cites MR0103, raise a technical query before you price.

What to check in a datasheet against a sour-service requirement

Use this table when a tender calls up NACE MR0175 / ISO 15156. Any gap becomes a row in your technical deviation list.

Sour-service checks on a valve or pump offer
Item	Check against	Typical deviation source
Edition and parts	Edition cited in the tender	Datasheet says NACE compliant with no edition, or cites an old pre-ISO edition
Service conditions	Process datasheet or specification	No H2S partial pressure, pH, chlorides or temperature given, so limits cannot be shown
Pressure-containing parts	Part 2 or Part 3 limits for the grade	Hardness or heat-treatment condition not stated
Trim, stem and springs	Part 3 limits for the alloy	Grade or condition outside its allowed limits
Bolting	Specification and owner standard	Standard bolting offered where a sour-service grade is needed
Welds and overlays	Weld procedure and hardness survey	No weld hardness survey offered
Certificates	ITP and VDRL	Hardness results missing; certificate type lower than required
Owner standard	Owner sour-service standard	Tighter limits or banned materials missed

Where OdysseyGPT fits

Sour-service requirements are often spread across the specification, datasheet notes, the ITP and an owner standard. OdysseyGPT reads the whole package, lists each requirement with a quote and page, and checks it against your own datasheets and material specifications. It does not qualify materials; a materials engineer decides. See OdysseyGPT for manufacturing and the datasheet vs specification checklist.

Buyer questions

20 questions bid engineers, proposal engineers and buyers ask. Last reviewed: 2026-10-23

What does NACE MR0175 / ISO 15156 cover?

NACE MR0175 / ISO 15156 sets requirements for metallic materials used in oil and gas production equipment exposed to H2S, often called sour service. Its aim is to prevent cracking caused by H2S, such as sulfide stress cracking. It covers how to select and qualify materials and the limits on hardness, heat treatment and environment for each material group.

What are the three parts of ISO 15156?

Part 1 gives the general principles for selecting cracking-resistant materials. Part 2 covers carbon and low-alloy steels, and the use of cast irons. Part 3 covers corrosion-resistant alloys and other alloys, such as stainless steels and nickel alloys. A tender that cites the standard as a whole usually means all three parts apply to the materials you offer.

Are NACE MR0175 and ISO 15156 the same document?

In practice, yes. NACE and ISO publish it jointly, so tenders often write NACE MR0175 / ISO 15156 as one requirement. NACE International is now part of AMPP, which still publishes the NACE-numbered version. Older specifications may cite a pre-ISO edition of MR0175. If the tender names an old edition or no edition, ask which one applies.

What is the difference between NACE MR0175 and NACE MR0103?

MR0175 / ISO 15156 is for oil and gas production, including upstream processing. NACE MR0103, with its ISO counterpart ISO 17945, covers sour refining environments. They have different scopes and different material rules. A refinery tender that cites MR0175, or a production tender that cites MR0103, is worth a technical query so both sides agree which one governs.

Who decides whether the service is sour?

The purchaser or equipment user is expected to define the service conditions, such as H2S partial pressure, pH, chlorides and temperature. The manufacturer then selects materials that meet the standard for those conditions. If the tender says sour service but gives no conditions, ask for them. Without them you cannot show that a material meets its environmental limits.

At what H2S level does ISO 15156 apply to carbon steel?

For carbon and low-alloy steels, Part 2 is widely read as applying once the H2S partial pressure in the gas reaches 0.3 kPa, or 0.05 psi. Below that, other factors can still matter, so the user may still call up the standard. Check the threshold and wording in the edition the tender cites rather than relying on this summary.

What hardness limit applies to carbon steel in sour service?

The best-known rule is a 22 HRC maximum for carbon and low-alloy steels, including welds and heat-affected zones, with conditions on heat treatment and composition. Other material groups have their own limits in Part 3. Tenders often ask for hardness results on the certificate or a weld hardness survey. Confirm the exact limits in the edition the tender cites.

What are common NACE MR0175 deviations in valve and pump tenders?

Common ones are trim or spring materials that sit outside their allowed limits, standard bolting offered where sour-service grades are needed, and no hardness results on the certificates. Another is a datasheet that says NACE compliant without naming the edition or the parts covered. List each gap as a row in your technical deviation list.

Does bolting need to meet NACE MR0175?

Sometimes. The standard treats bolting differently depending on whether it is exposed to the sour environment. Exposed bolting usually needs a sour-service grade with a hardness limit, such as ASTM A193 B7M with 2HM nuts, at some cost in strength. Many owner standards add their own bolting rules, so read the specification and state which bolting your offer covers.

What documents do EPCs ask for on sour-service equipment?

EPCs usually ask for a statement of compliance with NACE MR0175 / ISO 15156, naming the edition and the parts covered. They also want material certificates with hardness results, and often weld procedure records with hardness surveys. Some ask for HIC or SSC test reports for specific materials. These requests often sit in the ITP and the VDRL rather than the specification.

When do tenders ask for HIC testing?

Tenders often ask for hydrogen-induced cracking tests on plate and pipe made from carbon steel, especially for pressure vessels and line pipe in wet sour service. Valve and pump buyers ask for it less often, but some owner standards require it on certain product forms. Check the specification for named HIC test methods and acceptance criteria before you price.

Can I offer stainless steel trim in sour service?

Often yes, but only within the limits Part 3 sets for that alloy. Limits can cover temperature, H2S partial pressure, chlorides, pH, hardness and heat-treatment condition. Precipitation-hardening grades, for example, are allowed only in specific conditions. Check the tender's service conditions against the limits for your exact grade, and declare a deviation where they do not match.

How do I check my datasheet against a sour-service requirement?

List every wetted and exposed part: body, bonnet, trim, stem, seats, springs, bolting and welds. For each one, write the material, its condition and its hardness limit. Compare those with the service conditions in the tender and the edition cited. Then check that the certificates and test reports the tender asks for are in your offer and document list.

Is writing NACE compliant on a datasheet enough?

Usually not. Buyers want to know which edition, which parts, and which materials are covered. A bare NACE compliant note does not tell them if bolting, springs or welds are included. Name the edition and parts, and list exceptions. Where you rely on the user's service limits, say so, so the buyer can confirm them.

Do owner standards add to NACE MR0175?

Often, yes. Many oil and gas owners publish their own sour-service material standards. These can set tighter hardness limits, ban certain materials, or ask for extra tests. When an owner standard and MR0175 disagree, the order of precedence in the tender decides. See governing-document precedence and the Gulf owner spec checklist.

Can a material be used outside the listed limits?

The standard allows a material to be qualified for service outside its listed limits by laboratory testing or by documented field experience, under the rules in Part 1. That route takes time and the purchaser has to accept it. In a tender, treat it as a deviation or clarification, and do not assume the buyer will agree.

How does NACE MR0175 affect my material certificates?

Sour service often adds results the certificates must show, such as hardness values and heat-treatment condition. Some tenders also ask for a higher certificate type, such as EN 10204 3.2, on sour-service parts. Check what must appear on each certificate. See EN 10204 3.1 vs 3.2 for how the certificate types differ.

How does OdysseyGPT check sour-service requirements in a tender?

OdysseyGPT reads the whole tender package and lists each sour-service requirement, with a quote and page, from the specification, datasheets, ITP and owner standard. It checks each one against your own datasheets and material specifications and gives it a status, such as complies, deviates or clarification. You get an editable compliance matrix and a deviations and clarifications list.

Can OdysseyGPT tell me if a material is acceptable for sour service?

No. OdysseyGPT does not hold a copy of ISO 15156 and does not qualify materials. It can only compare the tender's requirements with what your own documents state, and show where each came from. A materials engineer must judge whether a grade and condition suit the service. Your engineers decide every open item and own the offer.

Frequently asked questions

Is NACE MR0175 a certification?

No. It is a materials standard. A manufacturer states compliance for the materials it supplies and backs it with certificates and test records; there is no NACE product certificate to buy.

Does NACE MR0175 cover general corrosion?

No. It addresses cracking caused by H2S. General corrosion and corrosion allowances are set by other parts of the specification.

References

ISO 15156 series: Materials for use in H2S-containing environments in oil and gas production

ISO

Buy the current edition from ISO or your national standards body.

Visit source

NACE MR0175 / ISO 15156

AMPP (formerly NACE International)