In order to properly size a blower system with a vacuum pump, there are five main requirements to consider:

How fast the customer would like to get to a base pressure in their vacuum chamber?

After they load the chamber, they then have to evacuate it down to certain pressure. This must be accomplished within a given time because, time is money, especially in manufacturing environment.

How to handle the gas load when we get to the base pressure?.

In most cases the roughing system is big enough to handle the gas-load, however this needs to be confirmed.

          Examples of applications:

          Vacuum furnace

          Vacuum coating – may have a flow of reactive gases

          Making computer chips to solar panels

 How deep a vacuum do they need to get to – what is the base pressure?

What is the rate of in-leakage going to be?

Do we have to overcome out-gassing from the chamber or the product?

The biggest problem that comes up time and again is how far away from the process the pumps are going to be located. In high vacuum applications the pressure drops are very significant. We have to evaluate the line size and diameter as well as if it is possible to get the pumps closer to the chamber to spend less money on the vacuum.

Another key area for sizing the blowers is a matter of modeling the thermodynamics of compression and making sure we avoid a thermal overload situation in the blowers. Rough vacuum systems are the most vulnerable to overheating in the range around 10 torr. Often times we are sizing blower systems for people who already have a primary vacuum pump selected. Sometimes we are selecting the correct size for maximum efficiency and type of pump with respect to process considerations such as condensable vapors or sensitivity to having oil molecules contaminating the product.

Solutions range from various oil sealed types of vacuum pumps to completely dry or liquid ring systems.

To learn more about proper blower sizing visit our website – www.aerzenusa.com or send me an email with your application question.

Bruce Impey
Vacuum Technology Specialist
bimpey@aerzenusa.com