Testing of alloy steel 1

[metboss]

Gents,
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 ??


Thank you

 

[redpicker]

My question is that without doing actual SSCC testing as per NACE TM-0177, how they can justify the above.

They can justify it because it is what is the standard says. If you are procuring equipment to meet ISO 15156 (NACE MR0175), you really should know what it says and what it means.

If so, then why API 5CT categorized various grades (L 80, T-95, C95…etc)?

L80, T95, and C95 are different grades. The requirements for testing and qualification of these grades are defined by the users. The different grades (C95, T95) are there so the users do not have to pay for NACE tested material (and other requriements, although the biggest difference between them is the NACE testing) when it is not needed.

Even without doing SSCC test, one can accept C95/4140 grade in lieu of T-95?

This is the real question. C95 grade from 4140 is not very likely to pass the NACE testing required by T95.

If C95 is acceptable, than, yes, it can be accepted. If T95 is required, then it is not.

It sounds as your supplier is trying to say that requiring T95 in this application is over-specifying the material and should not be needed. In part, this is irrelevant, if you clearly required T95 in your purchase specificaitons; that is, the supplier should have questioned the requirement and obtained approval for mateiral substitution, if acceptable, before accepting the purchase agreement. Conversely, if the purchase specifications only said the material had to meet ISO 15156 (NACE MR0175) for a specified set of conditions (that is, the purchase specifications did not clearly state T95 material is required), then the supplier is correct with his choice (provided the stated conditions were Region 2 exposure and temperature above 150F). The supplier may be trying to help you to accept "off-the-shelf" material and lower your costs and lead-times for equipment.

Where this goes next really depends on who is going to operate the equipment and in what environment it will be operated. The operator is the one ultimately responsible for making sure the material is suitable for the intended environment. It may be that, if T-95 is acceptable for all temperatures and C-95 is only acceptable for temperatures above 150F, the operator chose T95 since it would be acceptable regardless of the temperatures. If the operator can assure it will not be used at lower temperatures, it could be that what the supplier is saying is correct and that C95 would be just fine.

In my opinion, any time someone orders material that requires NACE testing, they should make sure the supplier fully understands what is expected in terms of testing and has accounted for such tests in the delivery promises. The testing itself takes 4 weeks and the requirement can easily add 6 months or more to the delivery, depending on material, not to mention added costs. While simply stating the requirements in the purchase specifications should be all that is needed, it is always prudent to make sure the supplier fully understands what is expected.

rp