Several principles for selecting vacuum pumps

Selection of vacuum degree: Define the vacuum degree required for actual operation under working conditions, commonly known as the vacuum degree requirement. For example, in the vacuum molding industry, it is required to reach -0.7MPa, and when selecting a vacuum pump, the vacuum pressure value must be at least -0.9MPa. So usually when we choose a vacuum pump, the vacuum degree is chosen to be half or an order of magnitude higher than the vacuum value of the vacuum equipment.

 

Vacuum pump pumping speed: The so-called pumping speed refers to the other quantity values that a cross-sectional area draws within a specified time. If the pumping speed is large, the time for the container to reach the vacuum value is relatively small. Conversely, if the change is slow, the selection of pumping speed range should consider the container and pipeline transportation situation. Usually, we can calculate it through the following formula:

PnSg ≥ PgS or

Sg ≥ Pgs/PnSg

 

- Effective pumping speed of the front stage pump

(l/s) Pn

 

- Critical pre stage pressure of the main pump (large exhaust pressure) (l/s)

Pg

- Vacuum chamber working pressure (torr)

S

- The effective pumping speed at Pg when the main pump is operating. (l/s)

 

Vacuum pump operating conditions: The so-called operating conditions mainly identify the composition of the air in the process, whether the gas contains condensable vapor, whether there is particle dust, and whether there is corrosiveness. When selecting a vacuum pump, it is necessary to know the gas composition and select the corresponding pump for the extracted gas. If the gas contains steam, particles, and corrosive gases, it should be considered to install auxiliary equipment such as condensers, dust collectors, etc. on the inlet pipeline of the pump.

 

The external environment that the working conditions need to meet: The external environment mainly refers to the environmental requirements of the actual application site, such as noise, pollution, etc. Different types of pumps need to be determined according to the actual situation requirements.

 

Consideration of the actual price and subsequent maintenance costs of vacuum pumps: Purchasing and maintenance costs are another key factor determining the purchase.