Difference between the NACE MR0175 requirements of SSC and HIC/SWC
Question: There is ambiguity between two passages, they contradict, paragraph 126.96.36.199 “SSC regions of environmental severity” of NACE MR0175/ISO 15156-2:2009 (E) to 17 Paragraph 8, “Evaluation of carbon and low alloy steels for their resistance to HIC/SWC” of NACE MR0175/ISO 15156 – 2:2009 (E) The paragraph 188.8.131.52 for Region 0 – For pH2S <0.3 kPa (0.05 psi) “ Normally, no precautions are required for the selection of steels for use under these conditions, whereas paragraph 8, says even trace amounts of H2S and shall consider HIC/SWC testing of these products” In addition the Sulfur restriction in the chemistry of.003% maximum.
“Your quoted passages of the standard are not contradictory. The standard provides different qualification requirements for different materials and different potential cracking modes. Clause 7 is for “- – steels with resistance to SSC, SOHIC, and SZC”. 184.108.40.206 & 220.127.116.11 are only applicable to SSC. Clause 8 is for “Evaluation of carbon and low alloy steels for their resistance to HIC/SWC”. For carbon steel products made from rolled plate, in addition to consideration of SSC resistance, HIC/SWC shall be considered (clause 8) and SOHIC and SCZ should be considered (clause 7.2.2).”
This question is in relation to NACE MR0175/ISO 15156-2 Clause 18.104.22.168
Reference: ISO 15156 Maintenance Panel Inquiry #2012-09