Selecting the Right Vacuum Pump for a 2 Lit Container

[bhaazee]

the pressure inside a 2 lit container has to be maintained at 0.01 bar. For this purpose, a vacuum pump will be used to pump the air outside. Also, air from atmosphere is leaking back into the container at 1 lit/min.

one of the following pumps has to be selected.

A. pumps out 10 lit/min
B. pumps out 3 lit/min

Both the pumps use the same power consumption, both don't need any special cooling process. What other factors will be affecting the pump selection. Which of the above suits best for the purpose?

note: this is not a homework question. have very little knowledge on Vacuum Technology.

Regards.

 

[Lsos]

I'm no expert either, but there are different types of vacuum pumps that work well at different pressures, and not at all at others, so a "lit/min" value is insufficient. A vacuum cleaner can surely pump more than a liter per minute, for instance, and yet I'm sure it will never get you to .01 bar.

 

[bhaazee]

http://www.pfeiffer-vacuum.com/prod...pace-10/onlinecatalog.action?detailPdoId=4518

Have a look at Characteristics. This is capable of achieving 0.01 bar pressure.

However, for the selection of pump have to find the leak-in rate. But, finding it difficult to determine the leak-in rate.

Thnx for the reply.

 

[Yuri B.]

Specifications of the pump you gave link to says it is 10 l/sec, not 10 l/min ! There will be very wide pressure swings in the container. How close +/- to 0.01 B it should be?
That the pump will cycle is not also good (with the "run-up time" - up to 90 000 rpm - 54sec !)
Maybe better to leave it run constantly, and control the pressure through a regulating valve?

 

[f95toli]

That link is to a turbo pump(!). There is certainly no need for that if you only need to reach 10 mBar. A turbo can reach pressures of about 10^-6 mBar, so it is quite literally more than a million times too good...

10 mBar is not even considered a vacuum, just about anything can reach that and 2l is not a very big volume. Just get a simple rotary pump, or even a diaphragm pump.

 

[Yuri B.]

Indeed - "Turbo" - 90 000rpm !
Maybe to look for a refrigeration vacuum pump - the smallest one to be found in the trade ?

 

[Yuri B.]

The pump (normal, not "turbo") speed controlled with an invertor with the invertor receiving signal from a pressure transducer. Qwestion : whether there are such pressure tr-s. ? (there should be)

 

[bhaazee]

Thnx for the replies. Opted for this turbo pump just for its tiny power consumption. However, the pumps is costlier.Also, the problem when proceeding with 0.01 bar pressures, is to find a right static and rotary seals. As, only costlier sealing solutions are available, moving to 0,1 bar and hence seem easy to find cheap and small vacuum pumps. Have found some miniature pumps but unfortunately upto 0.08 bar.

However, the problem is to find the leakage loss through the seals. Not many manufacturers are providing this info.

Thnx again for the replies.

Regards.

 

[MATLABdude]

I'm not a mechanical engineer, and hopefully someone else will chime in, but you may want to go to a library and read through the second chapter (Vacuum Science and Technology) of Milton Ohring's "Materials Science of Thin Films". It's a good primer on seals and various types of vacuum pumps (particularly for high-vacuum applications, which may or may not be higher than what you need).

Lesker has some nice general background information on vacuum seals (although it also focuses on the high-vacuum regime):
http://www.lesker.com/newweb/flanges/pdf/kjlced09_sec01_pages2-10_technicalnotes.pdf