Sep 12, 2026Procurement Guides
NACE MR0175 / ISO 15156: What Sour Service Means for Pipe and Fittings
NACE MR0175 / ISO 15156 sets the metallurgical requirements for carbon and low-alloy steel used in sour oil and gas service. Understand when it applies and why it matters.
Quick answer: NACE MR0175 / ISO 15156 is the standard that sets metallurgical requirements for materials used in oil and gas service containing hydrogen sulphide (H2S) - commonly called sour service. It matters because H2S can cause sulphide stress cracking in susceptible steels, so the material, hardness and heat treatment must meet the standard rather than being chosen on strength alone. Where a project is described as sour, pipe and fittings should be ordered to NACE MR0175 / ISO 15156 and the requirement should be stated explicitly.
What Sour Service Means
Sour service describes a wellstream or process stream that contains hydrogen sulphide. In the presence of moisture, H2S can drive cracking in certain steels, so the environment - not just the pressure - becomes a controlling factor in material selection. Equipment intended for sour service is therefore specified against a dedicated standard.
What NACE MR0175 / ISO 15156 Controls
The standard addresses the metallurgy of materials used in H2S-containing environments. It covers the material chemistry, the hardness limits and the heat treatment condition that must be achieved, because those are the factors that govern resistance to sulphide stress cracking. It applies across the range of equipment used in the wellstream, which is why pipe, fittings and other components are all assessed against it.
Why It Cannot Be Assumed
A pipe that meets an ordinary line pipe specification is not automatically acceptable for sour service. Higher strength is not automatically better - in fact, uncontrolled hardness is one of the conditions the standard exists to prevent. Sour service compliance has to be engineered and documented, which means it has to be requested on the enquiry and confirmed on the certificate.
In sour service, strength is not the objective - crack resistance is, and that is a question of metallurgy and hardness, not of grade number alone.
What to State on the Enquiry
State four things. First, that the service is sour and that NACE MR0175 / ISO 15156 applies. Second, the exact product - pipe, fittings, flanges or valves - and the material family. Third, the required hardness and heat treatment condition. Fourth, the documentation package, because sour service evidence travels with the material. Where the buyer works to an operator specification, quote that specification alongside the standard.
FAQ
What does sour service mean?
It describes oil and gas service where the stream contains hydrogen sulphide, which can crack susceptible steels in the presence of moisture.
Does NACE MR0175 apply to fittings as well as pipe?
Yes. The standard covers materials used in H2S-containing environments across wellstream equipment, so fittings and other components are assessed against it too.
Can a higher-strength pipe be used in sour service?
Higher strength alone does not qualify a material for sour service. Chemistry, hardness limits and heat treatment must satisfy the standard, so the requirement has to be specified and documented.
How do I order sour service pipe?
State that the service is sour, name NACE MR0175 / ISO 15156, give the material and the required condition, and specify the documentation package. Send your requirement and destination port to our engineering team.
Send your sour service requirement, material, sizes and destination port to our engineering team for a confirmed recommendation.
