NACE requirement for low alloy steel

[metboss]

Good day,

The client requirement for casing joint is material grade T-95 of API 5CT. We have submitted test certificates for the same, but grade mentioned in MTC is AISI 4130M and it meets the requirement of T-95 w.r.t chemical composition, mechanical properties, NDE, grain size & NACE TM-0177 method A tests. Now, client requires the test to be done in accordance to NACE MR-0175 and grade shall be AISI 4140. I am bit confused. My question is:
1) What is the difference between NACE TM-0177 & NACE MR-0175?
2) Why can't material 4130M be accepted in-lieue of 4140 even if it meets the requirement of T-95 grade?


Please advise me.

Thanks in-advance
Regards
Metboss.

 

[redpicker]

TM-01-77 is a test method, a method for performing corrosion tests to demonstrate resistance to H₂S.

MR-01-75 is a material recommendation, a recommendation for which materials to use in Sour Environments.

It sounds as if your client does not know enough about what he is talking about.

MR-01-75 requires the equipment operator to be responsible for insuring the material used is suitable for the environment, and gives recommendations on how to determine which materials will be suitable. It sounds as if, perhaps, he has done that by specifying API 5CT T-95 material. If T-95 material is acceptable, and your material meets T-95, then I am not sure what the problem is. Perhaps you will need to have your client show you what part of MR-01-75 he is trying to satisfy; that may clear up the issue. The point here is MR-01-77 requires the operator to define the conditions and requirements the material is to meet; not the supplier. THat is, the operator cannot just say, "It must meet MR-01-77" and leave it at that; but he can say "To meet MR-01-77, the casing and couplings must meet API 5DP T-95".

Incidentally, the likelihood of standard AISI 4140 being processed to meet the requirements of T-95 is slim-to-none. While the operator can say "I want AISI 4140 processed to meet T-95", but he is not likely to find anyone to supply him material without making concessions on the material composition. To pass the TM-01-77 Method A tests, you will have better luck with the lower carbon content, modified manganese, chrome, and moly contents, and lower P & S levels that are likely to be found in the 4130M (4130M is just a "modification" of the 4130 chemistry, with no specifics on precisely what has been modified, so it really does not, in itself, clarify much).

rp

 

[metboss]

Redpicker, thanks for your quick response.

Client's concern is that apart from NACE TM-0177 test results as mentioned in Material test certificate, additionally, NACE MR-0175 compliance shall also be mentioned in MTC by Mill (ex: Material test certifcate in compliance to NACE MR-0175).
But, Mill is declining it and now, clarifed that such thing need not be incorporated. My question:- "Is it mandatory to mention in MTC that supplied material is in compliance with NACE MR-0175"??

For second query my response is as follow: please comment......

"Both AISI 4140 & 4130 are low alloy steel and generally, all OCTG casing and tubing are manufactured from mother material: low alloy steel grades such as 4140, 4130, 4130M.

As far as the requirement of "chemical composition, mechanical properties and NACE TM-0177 test" are met against T-95 of API 5CT, then 4130M can be accepted in lieue of 4140.

Regards

 

[SJones]

ISO 15156 (NACE MR0175) places the onus on the end user to select and assure that materials are suitable for service in H2S-containing environments. Thus, manufacturers are right to shy away from stating compliance on inspection documents as they have no control over the environment in which the item will be used. It is down to the end user to check the information contained in the inspection documents and assure themselves that the material is fit for the service that it will be placed in.

Refer to the interpretation given to Inquiry 2006-13 at:

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

As to the second query, the issue could be understood in terms of the inspection documents not explicitly stating compliance with the defined purchasing standard, API 5CT; the 4130 versus 4140 argument appears to be going down yet another unrelated avenue.

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.