FAQ's

In NACE MR0175, What does”shall exhibit a threshold stress >=95% of the actual yield strength (AYS)” mean for UNS S41500?

NACE MR0175 / ISO 15156 in part 3, clause A.6, table A.22 requires impellers manufactured with martensitic stainless steel UNS S41500 to exhibit a threshold stress ≥95 % of actual yield strength in the anticipated service environment, this may involve testing as per NACE TM0177 2016.
We have helped clients to qualify UNS S41500 for sour service use.
Question 1:
In accordance with Table A.22 of NACE MR 0175 / ISO 15156-3 “Environmental and materials limits for martensitic stainless steels used as compressor components for compressor impellers in H2S-containing environments, S41500 steel is recommended. Please clarify the requirements of Notes “c” of Table 22, namely:
– in laboratory SSC tests, shall exhibit a threshold stress =95% of the actual yield strength (AYS);
– if the design stresses for the product are less than the actual yield strength (AYS) by a factor of 1.5, what stress level are allowed to be used in laboratory tests for SSC.
Answer 1:
Q: Regarding 15156-3 Table A.22 for UNS S41500, footnote “c” states if used for impellers, the alloy shall exhibit a threshold stress = 95% of actual yield strength in the anticipated service environment. If the design stresses are less than the actual yield strength by a factor of 1.5, what stress level is allowed in laboratory tests to demonstrate compliance?
A: Table A.22 requires the 95% threshold stress of the actual yield strength with no provision for lower acceptable stress levels; product/component design stresses are generally not covered by NACE MR0175/ISO 15156.
This question is in relation to NACE MR0175/ISO 15156-3/A.6.2
Reference MP inquiry #2017-08

The team at Oil and Gas Corrosion Ltd helps clients to define the qualification requirements for martensitic stainless steels used for compressor components. Talk to our team today!

Talk to an expert

Get in touch with us