Welding clips to explosion bonding plate

[daniel1978]

Guys

we are in middle of our TA, in one of our vessel (non pressure tower) i need to weld few clips ( to be permanent) however vessel plate is explosion bonded. so i have few questions to ask:
1- i assume we cant weld to EB plate ?
2- i ask foreman to grind the plate to get in to original plate then weld all clips and repair the cladding. is this correct action item?
3- repair locations has repair cladding does this repair make any issue in future ? (this will not the same as explosion bonding process) quality of cladding is not the same.

appreciate for your quick response

 

[DVWE]

You need to tell us what the EB material is, as well as the base material.

 

[EdStainless]

So the clips are on the process side?
Are they the same alloy as the clad?

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P.E. Metallurgy, Plymouth Tube

 

[daniel1978]

Base material is CS 516- GR70 and clad is 4 series SS.
clips will be in process side and same as cladding 4 series material .

 

[EdStainless]

How thick are the clad and base materials?
I assume that this is a ferritic stainless (very low C) clad, what composition is it?
The issue is that welding in ferritic filler may not generate enough strength.
It won't be the bond that fails, but the material itself.
If you strip, weld, and then weld overlay the overlay will not be as corrosion resistant as the clad.
And the overlay will need to be done in layers to minimize the C in the top surface.
You may need to use highly overalloyed material for the overlay.

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

You will need to locally remove the EB clad where the clips will be attached.
Next step, you will need to use Inconel 82/182 to attach the clip to the carbon steel substrate.
The clip attachment weld and surrounding exposed base material will need to be overlayed with nickel-base filler metal to ensure proper corrosion protection.

 

[weldstan]

Depending on corrosion mechanism and temperature you may not wish to use the nickel base filler metal. E/ER309 might be preferable.

 

[EdStainless]

Or if this not a pitting environment but and oxidizing one the FeCr ferritic overlay may be suitable.
Using 82 filler for the attachment is a good idea.

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P.E. Metallurgy, Plymouth Tube

 

[susan_cui]

my experience: depands on the force on the clip.
if the force is small, and clip material is same with cladding, I think it's OK to weld to EB directly.
otherwise, if the force is big, we need to move the cladding, the clip shall be welded to CS with acceptable filler metal. another option is to move the cladding, overlay on CS material firstly, then weld the clip with CS+overlay.

 

[jtseng123]

We have these in many vessels, especially for tray towers. Like susan cui says, depending on the stress.
If the stress on the attached "weld" (not the clip) is small, such as 4,000 psi and less, or 25% of the code allowable stress at the design pressure, we will allow clip directly weld to clad. For sure the clip is the same metal as clad. Also, the attached weld size can not be too big, otherwise, it will burn the clad.

If exceeding the limit, clip to be the same as base metal, strip the clad and directly weld to base metal. The use of clad plate for clip is also acceptable if not wanting to do weld overlay on clip. Most cases seen are for the beam seat.

As for weld metal for overlay, that is pretty much standard in every company or vendor's procedures, as well as follow API-582.

 

[SJones]

https://www.nobelclad.com/resources/design-considerations-in-attaching-pressure-vessel-internals

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.