Vacuum chamber weldment

By hogan

Date 05-01-2008 14:15

i think it is -15, but I'm sure someone will give a definite answer.

By Bill M

Date 05-01-2008 17:42

I thought the same...but couldn't confirm.

By ravi theCobra (**)

Date 05-01-2008 19:19

ASME applies over 15 PSI -

In many cases a vacuum chamber will be heavier walled than a simple pressure vessel -

By Bill M

Date 05-02-2008 16:41

I just want to make sure we do not need an ASME Stamp to fab

By Mikeqc1 (****)

Date 05-05-2008 17:26

I have asked this question ". Would a vessel need an ASME stamp if it ran @ -7 psi? "on the ASME forum and recieved this ........

Talking about a pressure vessel, not generating steam, not classified as Nuclear Item, and operating in the atmosphere, your -7psi partial vacuum means that there is 7psi external pressure from the atmosphere on the vessel shell.
It is not in the scope of Section VIII Div.1, because the pressure is less than 15 psi. However, the user may order it with Code Stamp, then ist shall be built in accordance with the Code.

Try this website.....
http://www.onetb.com/forum.htm

if the Address dosent work let me know
mike

By Bill M

Date 05-06-2008 18:39

Thanks for the link!

By G.S.Crisi (****)

Date 05-02-2008 17:59 Edited 05-02-2008 18:02

Yes, it falls under ASME VIII Code.
ASME VIII applies to vessels under an internal pressure of 15 psig minimum and any external pressure.
Hogan, minus 15 psig doesn't exist because minus 14.7 psig (equal to zero psia) is absolute vacuum, and it can not exist a pressure lower than absolute vacuum.
Regarding ASME stamp, Bill, it is up to the buyer (or customer) to require it or not. If your customer does require (and pays for) it, you have to satisfy his request. Of course, an ASME stamped vessel is more expensive than a not stamped one.
Giovanni s. Crisi
Sao Paulo - Brazil

By Heli-Arc (*)

Date 05-07-2008 20:11

On a vacuum vessel under Sect VIII, you have to run the calcs as external pressure.

Tom