ANSI/NACE MR0175/ISO 15156 requires carbon steels and low alloy steels to be HIC resistant. One way to confirm HIC resistance is by testing as per NACE TM0284, the acceptance criteria is as per NACE MR0175.
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Question: It appears that ISO 15156-2 is ambiguous in defining the acceptance criteria for HIC testing. Section B.5 and Table B.3 refer to NACE TM0284. This TM prescribes CLR, CTR, and CSR results to be reported for each of the three sections taken from a specimen and also as the average per specimen.
Q1. Could you please confirm that the intention of Section B.5 and Table B.3 is that the requirements of NACE TM0284 for the evaluation of test specimens should be followed and that CLR, CTR, and CSR should be calculated and reported for each section and the average for each test specimen. Table B.3 does not specify if the criteria apply to the single section numbers or to the averages per specimen or to the averages over a series of specimens. The last of these was suggested recently to us, for qualification purposes, by a materials manufacturer. ISO 3183-3 (the successor to API 5L) uses the same CLR, CTR, and CSR values as criteria as ISO 15156 but in addition it mentions that averages per specimen should be measured against the acceptance criteria (not single section numbers). I think it is common practice to apply this approach. If one decides that the acceptance criteria are to be applied to single sections, I do not believe that using, in addition, the same criteria for the average per specimen yields any useful additional information (because it is less restrictive), but it does no harm either. If, however, one decides that the acceptance criteria are to be applied only to the average per specimen, I am of the opinion that an additional condition should be imposed for single section results or for single crack lengths, for instance, no single crack length should exceed 5 mm, as part of the overall acceptance requirements.
Q2. Are the acceptance criteria intended to apply to the test results of both single section and the average per specimen?
Q3. Is the intention that, in coming to a qualification the CLR, CTR, and CSR values be calculated by averaging the results for a series of specimens?
Q4. If they are intended to apply to only the average per specimen, what additional requirements should be placed on the results of single section results?
A2. The referenced standard, NACE TM0284, Paragraph 8.4, requires the (calculation and) reporting of test results for each of three sections and the average for each test specimen. The application of the acceptance criteria to single section and/or the average for a specimen is subject to agreement between equipment user and the manufacturer.
A3. See Answer A.2 above, the referenced standard NACE TM0284 makes no mention of calculating results by averaging the results for a series of test specimens.
A4. The Maintenance Panel is unable to comment on issues that would involve an extension of the requirements of the standard. Any materials purchaser is free to add requirements beyond those required or made optional by the standard. Any amendment proposal to extend the requirements for single section test results must be submitted in accordance with the requirements outlined in:-
01. Introduction to ISO 15156 maintenance activities (Annex C) of the web site
This question is in relation to NACE MR0175/ISO 15156-2 Clause 8
Reference: ISO 15156 Maintenance Panel Inquiry #2006-11