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Skirt material for stainless steel vertical vessel
2

Skirt material for stainless steel vertical vessel

Skirt material for stainless steel vertical vessel

(OP)
Looking for advice on what material to specify for skirt for SA-376 TP304 vessel in cold service.

RE: Skirt material for stainless steel vertical vessel

I specify that structural materials that are welded to the pressure containing envelop shall be fabricated of materials that essentially the same as the head or shell to which they are attached. Consequently, I'd use SA240 Grade 304 plate material.

Regardless, you would want to make sure that whatever material you used, that the skirt material was suitable for the MDMT of the vessel for at least a distance equal to that which it could be affected by the vessel temperature. Figuring out this distance could be a bit of a problem so it's probably just easier to use 304 plate for the whole thing.

RE: Skirt material for stainless steel vertical vessel

I have seen SS vessels with a ring of the same material welded to the bottom head, to form the top of the skirt, and CS plate used below that. Depends on the size, number, as to whether that's economical or not, and whether long term corrosion protection is an issue.

RE: Skirt material for stainless steel vertical vessel

low temp a333 is the worst case.   you could use a333 for a foot or two then switch to a105 or grade B pipe for pipe diameter vessels if you believe the insulation is poor.

RE: Skirt material for stainless steel vertical vessel

What's your definition of Cold service (-45 C, -101 C or colder) ?  A333 is rated to -45 C.

RE: Skirt material for stainless steel vertical vessel

SKS....

What is the pressure vessel size ?

Is a skirt really necessary? Its usually expensive and only commonly used on tall distilation columns where there is no other choice.

I have always viewed a skirt design as inferior to a multiple leg design.

Additionally, implementation of load cells in the deign is very difficult when compared th a legged design,

Good discussion on legged design for vertical axis pressure vessels in the Bednar text (Pressure Vessel Design Handbook)

My opinion only

-MJC

   

RE: Skirt material for stainless steel vertical vessel

Petrochemical and Oil & Gas has always had a preference for skirt designs.  If you look at the Process Industry Practices (PIP) they allow leg designs under only certain limited situations if I recall correctly.

RE: Skirt material for stainless steel vertical vessel

PIP specify that the support should be SS for the portion of 2*(Rt)^0.5 but not less than 300 mm (12").  The lower portion can then be CS or low-alloy steel.

RE: Skirt material for stainless steel vertical vessel

I didn't realize PIP had specified a distance for the SS portion.  Good to know.

RE: Skirt material for stainless steel vertical vessel

Unless the skirts get very long, we generally just make the whole skirt stainless to keep from painting the carbon steel portion of skirt.

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