Low alloy steel corrosion testing

[metboss]

Good day !
We placed an order for some equipment to be used in a high temperature/high pressure well with H2S exposure, so the material has to be NACE MR0175 compliant. The required material grade is API 5CT “T-95”low alloy steel whereas manufacturer has supplied equipment fabricated out of C95/4140 grade Quenched/Tempered Steel. The main reason of rejection is deviation in grade & SSCC test (NACE TM-0177) which was not carried out by manufacturer as required by API 5CT for T-95 garde. Upon rejection, manufacturer has justified with following response:


“As per NACE MR0175 spec paragraph A.3 which states that any Cr-Mo Low ally steel in quenched and tempered condition is accepted for use throughout SSC Region 2.
C95 or 4140 Q&T should be suitable for sour service in any region if the service temperature when exposed to sour fluids is continually 150°F or above, as per NACE Table A.3”.

My question is that without doing actual SSCC testing as per NACE TM-0177, how they can justify the above. If so, then why API 5CT categorized various grades (L 80, T-95, C95…etc)? Even without doing SSCC test, one can accept C95/4140 grade in lieu of T-95 ??

 

[SJones]

It can't be justified. T95 is what was ordered; T95 is to be supplied. How do they know what Region applies now, or in the future? If you shut in a well, will the temperature stay above 65 deg C?

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.

 

[blacksmith37]

"C-95" is a mill's way of saying "We can't pass the T-95 / NACE Type 1 test" .
When T95 was first approved (over many mill objections) ,no mills in the western hemisphere could make it. Hopefully mills have gotten better since I retired; but they would have to prove it for me by passing by passing NACE test. Even if they claimed they were making T95.