PWHT & NDE on clad plate for wet sour service 1

[jtseng123]

Dear all,
This may have been talked before, but I just need to make sure what I am doing is correct:

For wet sour service, if carbon steel is used, our company spec asks 4 requirements: PWHT, full radiography, full penetration weld for all internal attachments, and all pressure parts must be normalized. But it does not talk about clad plate.

So if I use clad plate, such as SA516-70 cladded and weld overlay at seams/nozzles with 410S SS or 316L SS, all the above 4 requirements can be lifted, is it correct ? ( For CS base metal, we have mandatory requirement not to exceed 200 BHN, regardless what service)

 

[SJones]

Apart from the need for producing a company specification for clad vessels, the principal considerations are:

1. PWHT for service conditions: possibly beneficial to the carbon steel should the cladding be breached, possibly detrimental to the CRA
2. Full RT is probably driven by the consequences of a failure, and will probably apply to both carbon steel and clad
3. It is important to minimise stress raisers in both carbon steel and CRA
4. Normalising may be out of the question for a number of clad material options.

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.

 

[doct9960]

jtseng123,

This is based on my experiences (as a mechanical designer) on past projects...

For CS cladded vessels:
1. PWHT - Lifted, unless the ASME Code requires PWHT due to thickness.
2. Full Radiography - I have the same philosophy as SJones. It depends on the "criticality" of the vessel. For a critical piece of equipment, a few thousand dollars for 100% RT is worth the peace of mind.
3. Full Penetration - This depends on some factors...Owner preference, type of service (e.g. hydrogen service), or load. For wet sour service, I believe you don't need full pen., but some Client specs. or material specialists dictate otherwise. For vessels in hydrogen service, most Owners prefer full penetration welds on attachments. I believe fillet welds are sufficient in H2 service as long as there are gaps on the weld to avoid trapping hydrogen gases. Also depending on the load, fillet welds may not be sufficient on some heavy loaded attachments. Full penetration welds might be required. For heavy loads, I prefer the attachments to be welded directly on the base metal. We would require the fabricator to peel back the cladding, then full penetrationweld the attachment on the base metal, then weld overlay.
4. Normalizing - Lifted, unless a normalized material would be advantageous in avoiding the requirements of impact testing.

 

[wegm]

Supplementary, you could have a look at this link:

http://www.weldinguide.com/viewtopic.php?f=5&t=244

 

[jamesl]

I would like to know how full RT can prevent failure from wet sour service. If we are talking about criticality, you can apply that to any vessel, no matter it is in wet sour service or not.

To me the more relevant NDE for wet sour service vessel is WFMT on all internal welds after PWHT.

 

[SJones]

WFMT on a non-magnetic CRA?

Indeed, it is probably the sour service that drives the criticality ranking that then drives the NDT requirement. The NDT will not prevent failure, but it might identify anomalies that could initiate a failure.

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.

 

[jamesl]

Of course I was talking about carbon steel vessels in wet sour service. Once the vessel is cladded, there is no need for base material chemistry control, PWHT, hardness control, etc.

If we are talking about identifying defects that are related to wet sour servce, WFMT is a more effective method. I just don't see the relevance of full RT.

 

[wegm]

Sorry, the above link doesn't work, you could have a look at this link:

http://www.weldinguide.com/gdanastasiadis/viewtopic.php?f=5&t=244

 

[weldstan]

I would caution the use of 410 cladding. I assume it is 410S, 409 or 405. HAZ hardness in 410 ferritic type alloys after clad restoration may be somewhat high w/o PWHT. Regarding austenitic clad or weld overlayed carbon steel, agree with Steve.