PWHT for cladding vessel (H2S service) and layered blistering 1

[mechengineer]

Dear Experts,

Base material is SA516Gr70 and cladding is Incoel 625. H2S service.
1. My understanding is that it is not required PWHT due to H2S service for the cladding vessel because H2S is not contact to the base material of CS. Any different opinions with my view?
2. Cladding vessel after PWHT may cause layered blistering due to the different thermal expansion rate betwween base material and the cladding. Is it possible to make sure 100% no layered blistering after PWHT for cladding vessel?

Thanks.

 

[SJones]

1. Your understanding is correct if you believe that the cladding, including restoration at seam welds, is fully reliable in preventing fluid contact with the carbon steel weld zones. Note that ISO 15156 does not address H2S cracking of CRA weld metals, including weld overlay.
2. No it is not possible to ensure 100% complete bonding, but it is possible to institute NDT to maximise probability of detecting disbonded areas for subsequent evaluation and disposition.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[r6155]

See ASME VIII Div.1
Vessels or parts of vessels constructed of base ma￾
terial with corrosion resistant integral or weld metal
overlay cladding or applied corrosion resistant lining ma￾
terial shall be postweld heat treated when the base mate￾
rial is required to be postweld heat treated.

Regards

 

[mechengineer]

@Sjones,
Thanks for your input.
I'm struggling with Q2. Because I had experience with a cladding dished head being "swollen" after PWHT just last year.
Regards,

 

[Krausen]

I don’t believe the CS base metal needs to be PWHT in this case, as SJones stated. The VIII-1 reference from rb6155 applies if your base metal requires PWHT from a metallurgy perspective under VIII-1, which thin CS plate does not. VIII-1 does not prescribe requirements for PWHT of materials due to service environment. That is the user’s job.

 

[SJones]

@mechengineer
What was the particular method of cladding?

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[mechengineer]

@ Sjones,
Normally it is explosion bonded.

@Krausen,
This is client requirement for H2S service.
Besides, the PWHT is must in case of code required, such like the base material thickness being larger tham 1.5" (38.1 mm). In that case, we still face the same issue.

Regards.

 

[r6155]

There are various imperfections allowed. What is the required specification of the clad plate?.

Regards

 

[mechengineer]

@r6155, how to qualify the clad plate for PWHT is just my original question. There is nothing from client specification for this project.
Anyone come from the cladding plate manufacturers (QC)? welcome your oppinions.

Regards,

 

[r6155]

How do you know if disbonding was in the plate before PWHT?.
What specification of clad plate do you use for this project?
If there is nothing specification from the client then the PV manufacturer has the responsibility to select one.

Regards