316 SS support ring welded to clad vessel

[jtseng123]

Dear all,
By referring to the following link of discussion:

http://www.eng-tips.com/viewthread.cfm?qid=114267

I have a situation that a major load bearing support ring for catalyst bed has to be installed to a clad section (CS+316L SS)
The vessel requires PWHT.

Can I strip off the clad where the ring will be located, wled overlay min. of 3/16" thick to the stripped area as a buttered layer, then perform PWHT for the entire vessel. After PWHT, weld the 316LSS support ring to the buttered layer ?

(Our client is asking CS support ring (or clad ring on both sides) directly welded to base metal, and then WOL the entire support ring or stripped area. We are thinking doing other way as mentioned above)

 

[metengr]

Yes, you can do as you suggested but why PWHT the entire vessel? This makes no sense. Local PWHT is permitted by Code.

 

[metengr]

Local in the sense that a ring (soak band and heating band) is permitted around the entire circumference of the vessel.

 

[jtseng123]

metengr,
The vessel is mandatory PWHT for service reason. Do you think welding on top of buttered layer will impact the base metal such that aditional local PWHT will be required ? (We want to eliminate additional local PWHT due to the concern of different thermal growth between CS vessel and SS support ring that may damage the vessel wall or support ring)

 

[sanshu1111]

Jtseng,

If I understand it correctly, your client wants you to weld load bearing support ring directly on the base metal and not on the clad or weld overlaid surface.

In such case, you have to strip cladded section, weld the support ring, weld overlay stripped section and them PWHT. As per your proposal, support ring is welded on weld overlaid surface insetad of a clad surface which your client doesn't want.

 

[weldstan]

Jtseng
Weld cracking incidents in service had been reported at the location stated when welded per your desires. The Owner's requirements reflect methods employed many years ago to alleviate the problem.

 

[jtseng123]

weklstan,
All kinds of incidents can happen even under a good design.
Stress analysis (dead weight and thermal) can be done to prove it will be good, but is there any persuasive reason that load bearing support ring welded on top of WOL is no good ?

 

[weldstan]

Empirical evidence.