Repair job with R stamp, Hyderotest & derating query

[abuanaselmasry]

Dear respected members,

We did a repair job. The vessel is ASME U stamped built in 1975. Our job is to replace column boot with new fabricated boot in our shop. For the new boot, we did RT and hydrotest as per the requirements for a new vessel. We used the original design for the boot, however, we performed code calculation and stress verification during hydrotest.
We did the welding of the new boot to the original vessel. We conducted PT, Visual Inspection and pneumatic test for the repad only (leak test). As per contract and NB Inspector, this vessel is finished and the nameplate with R stamp is already welded to the boot. However, our client was insist to do hydrotest. Client used a stayed flat head in order to perform local hydrotest. But, this flat head get damaged during test before reaching the desired hydrotest value.
Now, our client needs us to de-rate the vessel to fit the actual hydrotest value. My questions are:

1- Is the hydrotest required and the NDE we have performed was really not sufficient to stamp the vessel with R stamp and it should be at least UT tested?
2- Is derating acceptable by NBIC? I'm referring to NBIC Part 3 para. 3.4.1 footnote 10?
3- API 510 3.56 allows for de-rating and actually this API standard is the main spec our client had established his specification based on. But, I'm confused between NBIC and API 510? Can we follow API 510 and also stamp the vessel with R stamp?

Sorry for the prolixity, but, I hope if you can reply me as soon as possible since we have to close this issue with our client within 2 days.

_________________
Regards,
M.Salaheldin

[abuanaselmasry]

Is my request so difficult to reply. or I presented it in wrong way?

Could you please help me on this since the issue is burning with our client and I don't know what to do?

[Wagolin]

I think you ´re having a legal problem more than an engineering one.

The document that supersedes any code (which are considered as a minimum requirement to fullfill) is the contract with the client to which both parties agreed by signing.

If the nb inspector agreed and stampted the part, then it means it is acceptable under nbic, with all the things this implies.

Everything relies on the legal background both parties agreed to fullfill. You may be debating for a long time on the engineering aspects of right or wrong but it won´t help you out in your actual situation.

Hope you get a solution!

[abuanaselmasry]

I totally agree with you that it is legal problem more than engineering. Even, there is no design problem at all.

I will till what we finally decided and please till is this OK or Not.

first of all the vessel is not installed in neither USA or Canda and there is not local jurisdiction which role the installation and repair of pressure vessels.
We convinced the client (Aramco by the way) that we will consider this job as two separate jobs. One for Repair and another for de-rating.
Repair job was 100% as per NBIC code and R stamp is applied.
De-rating job is as per API 510 and there is no involvement of NBIC.

Summary;
The vessel stamp is still valid since we are operating the vessel not beyond the limit of the vessel rating. After repair the vessel still can work at the original pressure temperature rating. However, the User decided to operate it at lower values. Original ASME Nameplate still shows the original rating. another nameplate (not stamped) will be attached near to ASME nameplate.

[Wagolin]

I agree....but above all, the most important thing is that your client is finally convinced with your solution and the problem is solved....everything else becomes an anecdote...

I´ve been involved in long, difficult debates about the aplicability of codes and standards exactly the way you described between parties and in my experience the best solution is to sign a very specific contract in which the extent of the job is clearly established, putting in writing the code or standard that covers the job and sticking to it...if you get a client to approve that, half the job is done...

glad you solved it...

regards...