The standards differ because ISO 15156 is dealing with H2S-containing service, and API Spec 5L is dealing with the manufacture of pipe. The sulphur restriction is weighted more heavily towards HIC resistance than SSC resistance, and it is to be noted that ISO 15156-2, A.2 addresses SSC, rather than HIC.

If you check API Spec 5L, Table H.1, you will note that the maximum allowable sulphur content is 0.003 mass % which miraculously coincides with the "certain user's" spec.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

The ISO 15156-2 / NACE 0175 addresses SSC, SOHIC, SZC, HIC, SWC. It may be noted that API 5L invariably makes reference to NACE for the corrosion mechanisms, corresponding mitigation thereof, and not vice versa.

HIC testing per NACE 284 is invariably specified for materials to be used in SOUR service and goes by the Crack ratios acceptance criteria.

The API 5L Annex H also calls for this testing. The restrictive sulphur content limitation is not called for in NACE.

It may be noted that API 5L Gr B pipe is often specified for SOUR service applications. The application of the Annex H is an optional one and requires a different designation for the API 5L pipe as in Table H1.

Yes, but your post specifically mentioned "A2," taken to mean 'A.2,' which addresses SSC ONLY, not the other damage mechanisms. HIC testing is most certainly NOT "invariably specified" as a search of the forums, using the term "HIC Testing," will show by the nature of the questions. The difference in the two specified sulphur levels is driven by the observation that lower sulphur steels are much more likely to give better HIC performance in H2S service

Apart from that, it's difficult to see what exact point you are trying to convey.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

The essential question that I have is that, I think that the NACE Std (which is currently the ISO 15156 parts 1 to 3) is more governing in terms for the corrosion mechanisms and mitigation recommendations than the API 5L. The recommendation that a 'A lower sulphur steel are more likely to give a better HIC performance' does not appear in the NACE standard. How does API 5L draw a conclusion which is not there in the NACE std. Moreover does API 5L imply that by using a Sulphur content of 0.003, the HIC testing can be done away with. Annex H2 i of API 5L lists it as 'alternative' HIC/SWC test methods and associated acceptance criteria.


Agree, ISO 15156 Annex A2 does cover only SSC. But if you see para 7.1 option 1 route, within this para it refers to the supplementary HIC tests through para 8.

When I said 'invariably' for the specification of HIC testing, this encompasses the SOUR service CS piping material specs seen around the middle east gulf.

When a pipe needed for a piping system intended to be used for SOUR service. This is the normal way of specifiying. API 5L Gr B + NACE ISO 15156. There is usually a supplementary statement in the Piping material specification that calls for the HIC testing in accordance to NACE 284 for welded pipes made from plates. The annex H of API 5L is not invoked.
The 0.003 % S is also applied over other CS piping components of ASTM specification.
Since the ASTM standard allows a higher sulphur content, this becomes difficult to achieve, unless a custom mill onder can be made.

Material specified for pipelines are usally mill order and it is not difficult to apply the restrictive compositions.

Annex H of API 5L says that the annex cannot be applied for PSL 1 pipes, although if one goes by the acceptance through the ISO 15156-2. thers does not seem to be a problem.

Quote (svi)

The essential question that I have is that, I think that the NACE Std (which is currently the ISO 15156 parts 1 to 3) is more governing in terms for the corrosion mechanisms and mitigation recommendations than the API 5L.

Well, that is pretty obvious as ISO 15156 is about cracking in H2S service; API Spec 5L is about making pipe. The API standard is not 'drawing conclusions,' it is setting requirements based on knowledge and experience. Clause 8 of ISO 15156-2 does give a hint as to the relationship of HIC performance to sulphur content in briefest terms, but with no actual requirements. The API standard is not so wishy washy. The reference to HIC in ISO 15156-2, 7.1. is a note for information, it is not mixing SSC and HIC. You might be reading more into this issue than there really is.

Annex H of API Spec 5L is not 'usually invoked' because the piping material specification is generally put together by piping engineers working in the past, particularly in the Gulf.

It's still not clear as to exactly what is being driven at here. Is it that PSL 1 pipe can be made to be PSL 2 pipe by some supplementary testing of pipe from stockists? The answer to that would be no - HIC resistance stems from steel design, steelmaking practice, plate rolling scedules, heat treatments etc, etc. Simply taking a piece of stock pipe and successfully HIC testing it is more demonstrative of good fortune, as opposed to HIC resistance.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

Thank you SJones.

Yes, there are stockists that try to offer PSL1 pipes with supplementary testing, but declined after asking for a TPI endorsement that it conforms to API 5L PSL2. Instead offers PSL2 pipes from stock.

APL 5L PSL-1 with NACE MRO175(In MTC), this pipe suitable for Sour service application?

That is for the end user to decide

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

in Addition to what is under debate here, I have a serious issue regarding the use of PLS2 or PLS1 for fitting in a sour service condition. As per API 5L 45th edition and again 45th edition, I repeat :), Is it mandatory to use PLS2 pipe for manufacturing fittings(forged or buttweld). or as the manufacturer claimed, they can use PLS1 pipes for sour service fitting with NACE MR0175, tests to be passed.

Thank you in advance if anyone can solve this issue that has been raised for sometimes in middle east fields.