psi of Tanks vs PV's

[tbrown87]

I have a question about tanks and pressure vessel pressures? I have what they are calling a PV but it is only running 5psi in the vessel? What is the difference between the two concerning psi? The only thing I see is that they have two heater tubes running through the vessel? Will this affect the status? I have read a few things on here and from what I can see 15 psi is the lower and upper for PV’s and tanks respectively? Oh ya this is in a LP plant.

 

[jte]

So what's an LP Plant?

As for vessels, it is entirely possible to have a vessel which normally operates no higher than 5 psig. Although it normally operates at that pressure, if its rated and stamped for a MAWP over 15 psi, then in many places that would be considered a vessel. Of course, the owner/user can also purchase stamped vessels with a nominal MAWP less than 15 psi if they choose. Sometimes it makes sense; I generally argue that in most cases it does not.

So remember, its MAWP that is the deciding factor, not your normal operating pressure or relief device pressure.

jt

 

[tbrown87]

The MAWP is 5psi at 450F. It is a Liquid Propane plant.

 

[jte]

Is it "U" stamped? If it is, then it's a vessel. End of story. Where (which country, what state) is this critter located? Are there jurisdictional rules which may come into play? There may be vastly different requirements in China vs Venezuela vs Canada.

jt

 

[tbrown87]

It is U stamped. This PV is in texas.
Well thank you for all the help with this!

 

[jte]

Well, Texas is a "looser" state when it comes to enforcing PV rules. They didn't used to require ASME VIII construction - I'm under the impression that has changed recently. If this is an existing vessel, there may be some "wiggle room".

Good luck!

jt