[labnetwork] house vacuum system

[Kuhn, Jeffrey G]

Good Morning Donghai,

The answers to your questions depend on the vacuum demand of your facility as well as the type(s) of gases the system would be seeing. If you are supplying vacuum to a large number of users, your best choice may be another liquid ring vacuum pump system since they can generate high cfm and therefore support a high demand. At Birck, our system comprises two Sterling (SIHI) liquid ring pumps rated at 500 cfm each. Only one pump is required to handle our demand, but they alternate duty cycles and the off-line pump serves as backup to eliminate single point failure.

There are some considerations when designing a liquid ring vacuum system:


1.       What level of vacuum is required? Typically, around -29” is as good as you can get from a liquid ring pump. That’s adequate for most non-process applications.

2.       Along with the level of vacuum, you must consider the service liquid (water) inside the pump. The higher the vacuum requirement, the cooler the service liquid needs to be. To achieve high vacuum, you may need a heat exchanger to cool the service liquid to the proper level. Keep in mind that if the service liquid gets too warm the pump will cavitate and ultimately destroy itself. I’ve seen that happen and it’s an expensive repair.

3.       The gases that the pump will be ingesting will determine its material of construction. If there are corrosive gases present you may need a stainless steel pump and internals.

In my career, I’ve dealt with SIHI, Gast, and Dekker systems. They are essentially the same in design and performance. That makes cost a major consideration, so I would consider sending it out for bid and specifying the performance parameters in the bid documents.

Others on this forum may have different opinions and I too would be interested in hearing them. Of course, if your vacuum demand is low, you may be able to go with a non-liquid ring design – perhaps even splitting the load between several.

Regards,

Jeff Kuhn
Facility Engineer
Birck Nanotechnology Center
Purdue University
1205 W. State St.
West Lafayette, IN 47907
Ph:  (765) 496-8329
Fax: (765) 496-2018



From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Donghai Zhu
Sent: Thursday, January 09, 2014 2:08 PM
To: labnetwork
Subject: [labnetwork] house vacuum system

Hello Colleagues,

We have a  house vacuum system for some process tools in clean room, such as aligner, spinner and vacuum container. We don’t use the vacuum for the cleaning of chambers and lab. The current vacuum system uses liquid ring vacuum pumps and it’s very old. We are going to replace it by a new vacuum system. Do you have any recommendation of the vendors and models of good vacuum system? Does it have to be a oil-less?

Thank you very much!

Donghai Zhu

Lab manager
Keck Photonics Lab,
University of Southern California
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