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.
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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.
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
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