VACUUM CONDUCTANCE
VACUUM CONDUCTANCE
(OP)
I have been tasked with designing a vacuum pipeline that will be connected to an existing vacuum pump. This is the first time I've delved into vacuum design. I've read about the term "conductance" and understand it to be akin to resistance. However, all the info I've uncovered merely addresses the conductance of long pipe. It does not address elbows, valves, and other pipe obstructions. Does anyone have a source that more completely addresses vacuum conductance? OR can anyone advise how one calculates and includes the conductance of the aforementioned obstructions? I know how to calculate overall conductance in series and parallel once all the various conductance values are calculated. I just can't calculate all the individual values.
Thanks for the help.
Thanks for the help.





RE: VACUUM CONDUCTANCE
http://www.tpub.com/utilities/95.htm
RE: VACUUM CONDUCTANCE
My line is going to be around 5 torr (0.1 PSI). I believe things get a little different at these low pressures.
RE: VACUUM CONDUCTANCE
RE: VACUUM CONDUCTANCE
Crane's TP410 gives you various methods to calculate pressure drop in gas flow though it doesn't specifically deal with vacuum applications.
Earnst Ludwig's Process Design for Chemical and Petrochemical Plants deal with vacuum piping design with worked out example.
When you deal with systems that deal with constant generation of gases, for ex. distillation systems, the design should base upon the the required vacuum in the equipment and the capacity of the vacuum pump. The difference is the maximum resistance that your selected pipe size should offer.
However, when there is no constant generation of gases and only if you have to evacuate a vessel, the maximum vacuum permissible by the pump can be acheived, in theory, irrespective of pipe size. But the fastness with which you can acheive this depends upon your pipe size.
RE: VACUUM CONDUCTANCE
If you want to research this area further, a great resource is the 2003/2004 Leybold Vaccumm Products and Reference Book (catalog, really). It has a 160 or so page section entitled "Fundamentals of Vacuum Technology". The newest version of the catalog omits this section, but I've been told it's available as a separate booklet.
Also, any technical sales person from a high vacuum pump company (Alcatel, Leybold, Ulvac, etc) should be able to help you out. My personal experience has mostly been with Leybold. They have been extremely helpful to me in the past.
Good luck!