FAQ's

Is HIC a potential risk if the partial pressure of H2S is below 0,3 kPa?

Risks of HIC (and SWC) are mentioned in Clause 7.1.2 / Note 3, and reference is made to Clause 8. Clause 8 underlines that HIC shall be considered as potential risk in sour service even if only trace amounts of H2S are anticipated. This is puzzling, and I’d like you to help me on clarification:
What does “trace amount” refer to? Is there a certain threshold? Is HIC not applicable as potential risk if the partial pressure of H2S is below 0,3 kPa (refers to Clause 7.1.1)? This interpretation is derived by the fact that HIC is not mentioned in Clause 7.1.1. On the other hand, this interpretation – on first sight – is not reasonable: As there is no threshold for H2S with regard to HIC (Clause 8), HIC -from my point of view – must considered as risk, and should be mentioned already in Clause 7.1.1.
The present ISO design implies that HIC only is of concern if Clause 7.1.2. is applicable. And this – in turn – is a contradiction to Clause 8. Please (1) clarify the misunderstanding / misinterpretation from my side and (2) advise on how to handle the risks of HIC in case of Clause 7.1.2:
Is Clause 8 valid or not?

ANSWER:
This inquiry pertains to Risks of HIC (and SWC) that are mentioned in NACE MR0175/ISO 15156-2 Clause 7.1.2 / Note 3 with reference to Clause 8. Clause 8 underlines that HIC shall be considered as potential risk in sour service even if only trace amounts of H2S are anticipated.
Question 1: What does “trace amount” refer to? Is there a certain threshold?
Answer 1: This is not defined in NACE MR0175/ISO 15156-2.
Question 2: HIC is not mentioned in Clause 7.1.1. Is HIC not applicable as potential risk if the partial pressure of H2S is below 0,3 kPa (refers to Clause 7.1.1)? Is  Clause 8 Valid considering that Clause 7.1.1 does not list HIC?
Answer 2: The NOTES in Clause 7.1 apply to both Clauses 7.1.1 and 7.1.2; for HIC and SWC, you are referred to Clause 8.
This question is in relation to NACE MR0175/ISO 15156-2 7.1.2
Reference: ISO 15156 Maintenance Panel Inquiry #2016-11

 

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