Question: There is ambiguity between two passages, they contradict, paragraph 7.2.1.2 “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 7.2.1.2 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.

Answer:

“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”. 7.2.1.2 & 7.2.1.3 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 7.2.1.2

Reference: ISO 15156 Maintenance Panel Inquiry #2012-09

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