Clad Plate use in Pressure Vessel need a Fabricator's view

[Flareman]

We are designing vessels (various 12 - 15 ft diameter) which each use a single shell belt of clad plate (mill bonded) which coincides with an internal wet process condition.
Cladding is 0.1 inch x AISI-317L over 7/8" 516-70
The plate, and hence the shell belt will be 8 ft wide.
The internal process section needed to be lined is only 7'-6" wide and there are (2) flat heads (just baffles with no real pressure requirement) dividing the vessel laterally.
These baffles are made from 2205 Duplex steel.

If we specify the cladding to be removed over 3.5" of the plate edge to permit the attachment of the 2205 to the base shell (and then overlay the inside weld for about 1/2") are we creating unnecessarily difficult work?

The other option would be to put the shell circ seam just inside the baffles but then we would probably need to crop the clad plate down to 7'-2" wide and weld overlay roughly 2" each side to keep the seam away from the internal 2205 plate edge.

Thanks for any advice

David

 

[SnTMan]

Flareman, any reason you can't just attach the baffles to the clad?

Regards,

Mike

 

[0707]

Flareman

Without knowing the details of you modification if I were you I would weld AISI 317L support rings for the baffles on vessel shell. The 2205 duplex plates would be fixed on the support rings through bolts and washers on oblong holes of support ring to absorb duplex plates expansion.

I feel that it is not your case, but if you need your baffles to be completely leak free the above suggestion doesn’t work.

Good luck

luismarques

 

[Flareman]

SnTMAN
I had originally thought that I might weld the baffles to the cladding but I'm uncertain about the strength of the shear bond between the clad and the base plate and the impact of a heavy weld (3/8" fillet?) from the baffle onto the very thin (0.1") cladding. Although the baffle is lightly loaded, it does carry a shear load, due to modest pressure differential, out from the vessel center toward the end, of roughly 150 lbf/in of circumference.
Do you have knowledge or experience that would allow me to believe this to be acceptable?

And yes 0707, because of this pressure load I do need to seal the baffle edges.

Thanks for jumping in
David

 

[arto]

Check the differential thermal expansion stresses for the different mat'ls the 2205 is closer to c.st'l. = might be problems welding it to the stainless.

Roark has a case like that (3rd ed. T.XIII c.9)- band on a shell (like having your belt on too tight ;-) )

 

[SnTMan]

Flareman, clad can commonly meet shear requirements of 20,000 psi. See Sec VIII, Div 1, Part UCL and/or SA-264 for example.

arto is right about 2205's thermal expansion, can you use a 317 baffle?

Regards,

Mike

 

[MJCronin]

Flareman...

How about some pictures ? I am confused about the arrangement...

Can you post a .jpeg or .gif of your configuration.... or perhaps a .dwg file. ?

I would put a corrugation in the baffle if there is a possiblity of it developing excessive thermal stresses

-MJC

 

[Flareman]

Thanks for everyone's interest but jobs like this have a habit of taking on a life of their own, no matter what the good advice stakes are.
The issue has largely resolved itself because the plate supplier has decided to come up with a narrower format so the amount of prep is minimized and I can weld the 2205 to the CS shell. The temperature differentials don't warrant a big concern about expansion and the 2205 is not so stiff that it can't flex a little in the extreme case.

Thanks again
David