317 thin sheet liner in large CS vessel. Experience needed!

[Flareman]

I have a 13ft diameter vessel in A-516-Gr70, which needs a thin 317 SS lining (approx 0.1 ins) in the bottom. The liner will only cover about an 8 ft wide arc and extend roughly 12" above the bottom of the vessel.
There will be nozzle penetrations into the liner. The edges of the nozzles will be coverered by welding the liner to the inner edges of the nozzles.
The outer rim of the liner will be welded to the shell.

Considering that the vessel may reach 500 degF in service, and there is a thermal expansion difference between the 317 and the shell, do I need to use any special details such as periodic plug welds, or reinforcing plugs around the nozles, to ensure that the expansion doesn't break out the very small edge welds at temperature.

Any previous experience welcomed.

Thanks
David

 

[jte]

David-

For the relatively small square footage you're dealing with, I'd suggest going with weld overlay instead of a liner. As you suspect, welding a thin liner has its issues. No matter how well you do it or how many plug welds you have. All it takes is for one to crack and now you're dealing with a large crevice which you'll have to tear out in the field (cold work only since you can't clear the crevice...) and replace with weld overlay... Been there, done that... Bad if it's a planned job, worse when it is discovery work during a turnaround.

jt

 

[JoeTank]

For such a small tank you could also consider replacing the lower portion of the tank with solid 317 material. It may cost more, but would be better than a liner.

Joe Tank

 

[gr2vessels]

Flareman,
If you HAVE to use the liner, you should consider making the liner as loose as possible, with sufficient fold at the welded edge (the liner outer edge), and give it a good weld to the nozzle neck (I assume the nozzle is located in the centre of the bottom head). However, all this depends on your secret process that you were reluctant to share with us. Any solids to crush the liner? Is the process fluid a gas? Only liquid separation?
Cheers,
gr2vessels

 

[Flareman]

Thanks for all the advice.

The use of the liner is dictated initially by the client but I propose to dicuss it further with his engineers. The problem with weld overlay is always the $$$.

No secrets to this process, it's a hydrocarbon gas filled separator with a water seal on the inlet. There's a long term corrosion issue because of the water and possible dissolved acidic materials. Only the lower (wetted) parts get treated with liner.

I didn't say before that it's a horizontal cylinder, so that complicates the possibilities of folding the liner to enable expansions because the vessel walls still have to drain downward.
However, I do have a couple of ideas.
One involves adding a more substantial SS strip or pad to the inside of the vessel to receive the welded edges of the liner. That way the strip and the liner are the same material and the differential stress is confined to the heavier section where I can define the amount of weld to be used.
The other would use dimpled material, (dimples up) to absorb the movement.

It's all still up in the air!!

David