Pressure Vessel - Full Vacuum Capability? 1

[ChEMatt]

I have an existing vessel that doesn't seem to have a vacuum rating, or no minimum pressure listed. To be honest I'm not sure if that information should appear on the U-1A or not, but that's the only document I have. Well, there's also a U-4 and a U-2A but I don't see a vacuum rating anywhere.

The info on the vessel - MAWP 50 psig, min design temp -20 @ 50 psig, shell is SA-240-304L, nominal thickness is 0.250". Diameter is 84" and it's 56'1" seam to seam. Elliptical 2:1 heads.

The vessel (an amine still column) is going to run at about 240 F and 14 psig. I need to determine whether or not it can handle full vacuum should it get isolated and cool down to ambient. Is there a way to determine this?

Thank you for your help!!

-Matt

 

[TomBarsh]

If the vessel was designed for external pressure then it should be stamped on the ASME nameplate and would be on the U-1A form.

Just a quick calculation: An 84" ID cylinder x 0.25" thick x about 674" long (omitting consideration of the heads), SA-240 304L, has an MAEP of about 1.3 psi. That's nowhere near full vacuum.

 

[ChEMatt]

Thanks Tom. That's enough for me to try to get our MechE department involved to get a confirmed number. I didn't think anyone was available but someone walked in after I posted.

Thank you!!

 

[racookpe1978]

If you cannot get the vessel "protected" by design calculation against a "full vacuum", then add a vacuum relief valve in an unsolvable position.

 

[JohnGP]

Hi Matt,
As Tom indicates, vacuum capability can be calculated. To achieve full vacuum rating would require stiffeners on the shell roughly 6' apart, so some form of vacuum relief may be cheaper.
Cheers,
John

 

[racookpe1978]

If you cannot get the vessel "protected" by design calculation against a "full vacuum", then add a vacuum relief valve in an unsolvable position.

D*mn misspell checker.

Rather: If you cannot get the vessel "protected" by design calculation against a "full vacuum", then add a vacuum relief valve in an unisolable position, a place you cannot isolate it.