Selection of vacuum pump, you need to note the following: 1, the working pressure of the vacuum pump vacuum equipment should meet the ultimate vacuum and pressure requirements. Such as: vacuum coating requires 1 Ã— 10-5mmHg of vacuum, the vacuum of the vacuum pump used at least 5 Ã— 10-6mmHg. Usually choose the degree of vacuum pump is higher than the degree of vacuum vacuum equipment to an order of magnitude. 2, the correct choice of vacuum pump working point. Each pump has a certain range of working pressure, such as: diffusion pump 10-3 ~ 10-7mmHg, in such a wide range of pressure, pump pumping speed varies with pressure, and its stable working pressure range of 5 Ã— 10 -4 to 5 Ã— 10 -6 mmHg. Therefore, the operating point of the pump should be selected within this range, but can not let it long-term work under 10-8mmHg. Another example of titanium sublimation pump can work under 10-2mmHg, but its working pressure should be less than 1 Ã— 10-5mmHg as well. 3, the vacuum pump in its work pressure, should be able to drain away all the gas generated in the process of vacuum equipment. 4, the correct combination of vacuum pump. Due to the vacuum pump selective suction, therefore, sometimes the choice of a pump can not meet the pumping requirements, the need for several pump combinations, complement each other to meet the pumping requirements. Such as titanium sublimation pump high hydrogen pumping speed, but can not helium, and the triode sputtering ion pump, (or bipolar asymmetric cathode sputtering ion pump) has a certain pumping speed argon, both When combined, the vacuum will get a better degree of vacuum. In addition, some vacuum pumps can not work under atmospheric pressure, requiring pre-vacuum; some vacuum pump outlet pressure below atmospheric pressure, the need for fore-stage pump, it is necessary to use the pump combination. 5, vacuum equipment, oil pollution requirements. If the equipment is strictly required oil-free, should choose a variety of oil-free pumps, such as: water ring pump, molecular sieve adsorption pump, sputtering ion pump, cryogenic pump. If the requirements are not strict, you can choose a pump, plus some anti-oil pollution measures, such as adding cold trap, baffle, oil well, etc., but also to achieve clean vacuum requirements. 6, to understand the composition of the gas being drawn. Gas containing non-condensable vapor, with or without particulate dust, whether corrosive and so on. When choosing a vacuum pump, you need to know the gas composition and select the appropriate pump for the purged gas. If the gas contains vapors, particles, and corrosive gases, consideration should be given to installing auxiliary equipment such as condensers, dust catchers, etc. on the pump inlet piping. 7, the vacuum pump discharge of oil vapor on the environment. If the environment does not allow contamination, you can choose oil-free vacuum pump, or the oil vapor to the outside. 8, the vibration generated by the vacuum pump on the process and the environment have no effect. If the process is not allowed, should choose no vibration pump or take anti-vibration measures. 9, the price of the vacuum pump, operation and maintenance costs. In the case of the use of permits, should try to use cheap vacuum pump.