Vacuum on Pressure Vessels
Vacuum on Pressure Vessels
(OP)
Hi,
I am new to the comncept of vacuum relief. What is exactly the definition of "vacuum" on a vessel (or full vacuum). What codes show how to calculate if a vessel can handle vacuum conditions or if a vacuum relief valve is needed.
Thank You
I am new to the comncept of vacuum relief. What is exactly the definition of "vacuum" on a vessel (or full vacuum). What codes show how to calculate if a vessel can handle vacuum conditions or if a vacuum relief valve is needed.
Thank You





RE: Vacuum on Pressure Vessels
To design for vacuum relief, decide what external pressure should be the MAXIMUM for design purposes. Then provide a measure such that said maximum is not exceeded.
RE: Vacuum on Pressure Vessels
Thanks for the reply.
RE: Vacuum on Pressure Vessels
If you can find a copy of the Ingersoll Rand pump book (any any pump book for that matter), it will discuss suction pressure/vacuum with some sketches which should help you understand it vaccum relative to atmospheric pressure (vacuum isn't an absolute number. Rather, it's used to refer to any pressure less than atmospheric).
As Elquero put it, since 14.7 psia is atmospheric pressure at sea level and the minimum pressure that could exist in the vessel is 0 psia the maximum vacuum rating is 14.7 psi.
RE: Vacuum on Pressure Vessels
RE: Vacuum on Pressure Vessels
"Vacuum" is probably easier to understand in terms of external pressure instead a lack of internal pressure. A vessel that is open to the atmosphere (in equilibruim) is under no vacuum (no external pressure). If you close the vessel and evacuate enough fluid to reduce the internal pressure to 10 psia, the vessel would be under a 5 psi vacuum (total external pressure (assumed 15 psia) - 10 psia internal pressure = 5 psi vacuum). Obviously in this situation, the maximum vacuum (full vacuum condition) would occur when there is no internal pressure (0 psia).
There are equations used to calculate the required thickness for a given external pressure. Check the Pressure Vessel Hamdbook by Eugene Megyesy.
Hope this helps.
Jproj
RE: Vacuum on Pressure Vessels
RE: Vacuum on Pressure Vessels