PWHT on Monel Claded material

[SJEC]

I am working on horizontal tank fabricated in 1958.
the bottom half of the shell is monel 400 claded 1/8", base mareial 1.2" A212-B FBX. Now, I need add a new nozzle on it.

Question.
1. I only have ASME Code 1949, It looks like all welded PV had to perform PWHT at that time. Is here anybody have ASME 1958 to help me confirm if the vessel require PWHT due to mechanical reason. 1.2" CS did not require PWHT as per current Code.

2. The vessel is working in sour service. I beleive it is the process reason for PWHT. The new nozzle is located in claded area. Since the new nozzle did not direct contact process liquid. Can I avoid PWHT?

3. In case PWHT is required, If the PWHT will effect the corrosion resistance of the monel or break the bound between monel and CS?

Thanks

 

[SJones]

Tank or pressure vessel?

If a pressure vessel, the vintage of the steel is such that it will be difficult to meet the hardness requirements of ISO 15156 or NACE MR0103, whichever is appropriate, without PWHT. You could try performing a test on the coupon extracted for the nozzle to check this supposition. It is a distinct possibility that hydrogen generated by the H2S reaction with the unclad steel could have permeated behind the cladding and will continue to do so. Therefore, requirements for H2S service will probably still have to apply.

If your arguments fail, PWHT will not damage the Monel (assuming 400) and should not disbond the cladding. If it was going to disbond, it would have done so already and pre-welding NDT should pick it up. However, you should investigate appropriate hydrogen removal procedures for application prior to welding.

Steve Jones
Materials & Corrosion Engineer

http://www.oilandgaspeople.com/cv/11499664

http://www.linkedin.com/pub/8/83b/b04

 

[jamesl]

I have access to 1956 Ed, 57 Addenda. SA 212 material require PWHT for weld thickness over 1" per UCS-56(3).

If you need to add a new nozzle with full penetration weld, PWHT is required by code.

My understanding is cladded (or weld overlayed) vessels do not have to follow all wet H2S requirements on CS as long as the weld overlay meets the hardness requirement in NACE MR0103.