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AIR GAP INSULATION

AIR GAP INSULATION

(OP)
Hi All
I am working on a gas plant upgrade project and there is a requirement to apply "air-gap insulation" to vertical and horizontal pressure vessels. The air gap insulation is basically a 50mm air gap on the outside of the vessel shell/ends and a stainless steel sheeting is then applied. There is no sold insulation material behind the sheeting-only air. This makes the sheeting susceptible to buckling as it is only supported at approx 1.2m lengths by an angle section (50mm x 50mm). There are are also issues at nozzles where the sheeting needs to be supported and also issues in applying the sheeting/shaping it to fit around the 2:1 SE dished ends.

We could apply numerous clips/supports on the outside of the shell and ends - but this is not preferred obviously due to time and money.

Has anyone applied air gap inulation as detailed above to vessels before? Some details of the set-up would be most helpful.

Thanks

RE: AIR GAP INSULATION

rocai I have applied air-gap insulation partially to the inside of a fairly large vessel, or perhaps it was a heat shield, nobody was sure which. It was a very complicated set of details without being of proven effectiveness :)

Recommend you study Sec VIII, Div 1, Appendix 9 for typical jacketed vessel rules and details. If you are concerned about potential bucking, use more steel.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: AIR GAP INSULATION

(OP)
Thanks Mike
This is not a pressure item and has nothing to do with ASME VIII. It is basically a thin sheet cover around the vessels allowing a 50mm air gap between the outside of the shell and the inside of the 0.9mm thick sheeting.
Sorry if my post was not clear.
The only loads the sheeting will see are if someone leans on it or possibly during high winds if insufficient supports are applied.

RE: AIR GAP INSULATION

roca, no, I understood it was not pressurized, just offered Apx 9 for some typical details. I'd say a heavier sheathing might help to minimize the required internal supports, etc. Differential thermal expansion may need to be considered as well. A couple of vent & drain connections might be useful also.

Good luck with it...

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: AIR GAP INSULATION

Lighter weight is (almost always) cheaper, easier to flex during heatup/cooldown. The heavy supports will restrict movement of the air gap plate, but also restrain the pressure vessel plates and heads.

Windloads need to be considered, but the air gap is as effective with many studs or offsets holding the thin plate as it is with heavier (more expensive) thick angle iron and stiffeners in only a few places. Don't overthink the problem.

Sounds like they are trying to create a radiant barrier, perhaps using it also as a safety standoff barrier around the hot PV.

RE: AIR GAP INSULATION

roca. You can use an integral reinforcing in each cylindrical section, like a small bellow expansion joint 2 to 3mm height, 50 mm wide aprox. This is made during rolling the plate 0,9 mm. No welding, no angle section.

Regards
r6155

RE: AIR GAP INSULATION

I second what r6155 says (If I'm understanding it correctly). If you can get some thin sheet rolled with your 50mm standoff, it's going to be the most efficient design. No welding, no impact on the PV. It really shouldn't be a big deal for a sheet metal worker.

Jim Breunig P.E.
XCEED Engineering
Mechanical Engineering
FEA Consultants

RE: AIR GAP INSULATION

(OP)
Thanks All

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