2 replies to this topic

[ogpprocessing]

Dears,

For which applications the pressure vessel (2 or 3 phase separator, column and etc) should be designed for full vaccum condition? On the other hand when FV (full vacuum) is specified as minimum design pressure of the vessel?

I know steam out case that covers this requirement. Do you know other cases?

[ankur2061]

ogpprocessing,

The links below should provide you the answer:

http://www.cheresour...__fromsearch__1

http://www.cheresour...h__1#entry27626

Regards,
Ankur.

Edited by ankur2061, 22 September 2011 - 03:55 PM.

[djack77494]

The threads referenced by Ankur provide a lively discussion of the issue of full vacuum designs. I personally have been standing besides a tank into which a large quantity of flushing water was suddenly and mistakingly dumped into the tank (through the vent line as it turned out). The water overflowed the tank, and in the ensuing confusion the vent was closed and then an attempt was made (in haste) to empty the tank. The end result was a vacuum which caused the collapse and total loss of the tank, but it could have easily been more catastrophic.

Probably as a result of this, I have great respect for the power of vacuum conditions to wreck havoc on vessels. I do not subscribe to the notion of "half vacuum". If you can generate half an atmosphere of negative pressure and do not have positive means to prevent even lower pressures from developing, then design the vessel for "full vacuum".

You've gotten a number of situations that could result in a vacuum developing. Most common are negative pressure process conditions, steam out, and, as I've just demonstrated, even just flushing and emptying. The latter two situations can be and often are managed with administrative controls - just stating that vacuum will not be allowed to form due to keeping open vent lines, etc. That's an administrative decision and is far above the abilities of a lowly process engineer to determine. Personally, I don't like the administrative controls approach and like for my designs to be as foolproof as practical.

Edited by djack77494, 22 September 2011 - 05:04 PM.