The function of vacuum pump is to remove gas molecules from the vacuum chamber, reduce the gas pressure in the vacuum chamber, and make it reach the required vacuum degree. Generally speaking, there is a large range from the atmosphere to the extremely high vacuum, which has not been covered by a vacuum system so far.

Therefore, in order to meet the requirements of process index, work efficiency and equipment service life of different products, different vacuum section needs to choose different vacuum system configuration. In order to achieve the best configuration, the following points should be considered when selecting the vacuum system:

1. The limit pressure of vacuum pump should meet the working pressure of the process. Generally, the limit pressure of the pump is lower than the process requirement by about an order of magnitude.

2. Each kind of pump has a certain working pressure range, therefore, the working point of the pump should be selected in this range, instead of allowing it to work at the allowable working pressure for a long time.

3. Under its working pressure, the vacuum pump should be able to discharge all the gas produced in the process of vacuum equipment.

4. Select vacuum unit:

(1) When one kind of pump can not meet the requirements of air extraction and vacuum, several pumps need to be combined to supplement each other to meet the process requirements.

(2) Some vacuum pumps can not work under atmospheric pressure and need pre vacuum; some vacuum pumps with outlet pressure lower than atmospheric pressure need front stage pumps, so they need to be combined. The combined vacuum pump is called vacuum pump unit. It can make the vacuum system get better vacuum degree and air displacement. We should choose the combined vacuum pump correctly, because different vacuum pumps have different requirements for the gas to be removed. For example, in general, roots rotary vane unit is not suitable for the system containing more condensable gas.

5. When you choose an oil sealed pump, you should first know whether your vacuum system has requirements for oil contamination. If the equipment is strictly required to be oil-free, all kinds of oil-free pumps should be selected, such as: water ring pump, low-temperature pump, etc. If the requirements are not strict, you can choose to have an oil pump, plus some anti oil pollution measures, such as adding cold trap, oil trap, baffle, etc., can also meet the requirements of clean vacuum.

6. Understand the composition of the extracted gas, whether there is condensable steam in the gas, whether there is particulate dust, whether there is corrosiveness, etc. When choosing the 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 gas, it should be considered to install auxiliary equipment such as condenser and dust collector on the air inlet pipeline of the pump.

7. When choosing oil seal vacuum pump, the influence of oil vapor (oil fume) discharged from vacuum pump on environment should be considered. If the environment does not allow pollution, oil-free vacuum pump should be selected, or the oil vapor should be discharged to the outdoor.

8. If the process is not allowed, the pump without vibration should be selected or anti vibration measures should be taken.

9. The price, operation and maintenance cost of vacuum pump.

After considering various situations, you can finally determine a solution that is suitable for you:

(1) Minimum investment cost.

(2) Minimum production and operation cost.

(3) The feasible scheme of reasonable and uniform distribution of the first two cases.