The application of austenitic stainless steels for instrument as per NACE MR 0175 (ISO-15156) 1

[Lee SiHyoung]

Dear Experts,
Referring to table A.6 of NACE MR 0175 -3 (ISO-15156-3), the application of austenitic stainless steels seems no limitation from temp,H2S & chloride while there are tougher restrictions in Table A.2.
Although it is same materials as austenitic SS with same fluid, does that mean it is possible to apply the higher grade (ex., nickel alloy) for piping while the connected instrumentation can be designed as SS 316L as optimized?
If yes, what is the technical background behind? (Is it due to stress consideration???)
Thanks in advance.

 

[pradipgoswami]

Table A.2 — Environmental and materials limits for austenitic stainless steels used for any equipment or components has very little or No restriction Up to 60 Deg C & 100 KPa of H2S partial pressure.

Table A.6 — Environmental and materials limits for austenitic stainless steels used in compressors-and instrumentation and control devices:Austenitic
stainless steels:These materials have been used for these components [highlight #FCE94F]without restriction on temperature, pH2S,Cl−, or in situ pH in production environments.[/highlight] No limits on individual parameters are set but some combinations of the values of these parameters might not be acceptable. [highlight #8AE234]Yes the answer is open ended.[/highlight]

In the context of the above it may be worthwhile to go through this document:

http://www.iso.org/iso15156maintenance,3rd

December 2015 the Q&A on page 60.Use of superior materials.The applicability of Table A.6 to specific components must be agreed between the user and manufacturer.


Hope this would be of help.
Thanks.

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299
All provided answer are personal opinions or personal judgements only. It's not connected with any employers by any means.

 

[Lee SiHyoung]

Hi.pradipgoswami. Thanks for the reply. But the answer is not so clear to me.
What is the meaning of "open ended"? Does that mean Table A.6 which does not have any limitations is not valid or it is something that shouldn't be fully followed?
If you can, I appreciate why the different table is applied.(why instrumentation is having no restrictions from corrosion aspect?) Also, the link is not available. (Would you please check it too?)
Thank you very much!

 

[SJones]

http://isotc.iso.org/livelink/livel...c=ll&objId=3340364&objAction=browse&sort=name

"open ended" means that there is no definitive answer. It will become even more open ended when reading the interpretation for Table A.6 in the above document.

The difference in allowable parameters between Table A.2 and Table A.6 is simply a result of transposing the original NACE MR0175 into ISO 15156-3 without a rational basis, other than a group belief that the items don't fail whatever they are exposed to as observed somewhere in the mists of time.

Does the end user of the equipment subscribe to this group belief?



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.