1, Vacuum pump work pressure should satisfy the requirement of the vacuum equipment ultimate vacuum and work pressure.Such as: vacuum coating require for 1 x 10-5 MMHG vacuum degree and choose the vacuum degree of vacuum pump must be at least 5 x 10-6 MMHG.Usually choose the vacuum degree of the vacuum pump is higher than vacuum degree of vacuum equipment for half to one order of magnitude.
2, Correctly select the vacuum pump working point .Each vacuum pump has a certain working pressure range, such as: oil diffusion vacuum pump for 10-3 ~ 10-7 MMHG, in such a wide pressure range, the pumping speed of the pump vary with the pressure change, its stable working pressure in the range of 5 ~ 5 x 10 x 10-4-6 MMHG.Therefore, the working point of the pump should be selected in this scope, but can’t let it work for a long time under 10-8 MMHG., such as titanium sublimation pump can work under 10-2 MMHG, but its working pressure should be less than 1 x 10-5 MMHG.
3, vacuum pump in its working pressure, should be able to come in during the process of vacuum process equipment of all gas volume.
4, properly combined vacuum pump.Due to the vacuum pump in selective extraction, consequently, sometimes choose a kind of pump can not meet the requirement of the extraction, need several pump combination, complement each other to meet the requirements of extraction.Such as titanium sublimation pump for hydrogen has a high pumping speed, but it can’t take helium, sputtering ion pump and three pole type, type (or two extremely asymmetric cathode sputtering ion pump) to the argon pumping speed to a certain extent, the two together, will make the vacuum unit get good vacuum degree.In addition, some vacuum pump can’t work under atmospheric pressure, to a vacuum;Before some vacuum pump outlet pressure is below atmospheric pressure, need to pump, pump old need combined use.
5, vacuum equipment requirement for oil pollution.When vacuum equipment strict require oil free, should choose all kinds of oil pump, such as: water ring vacuum pump, molecular sieve adsorption pump, sputter ion pump, cryogenic pump, etc.If not strict, you can choose to have the oil pump, add some oil pollution prevention measures, such as a cold trap, mask, block oil well, etc., can also meet the requirements of clean vacuum.
6, understanding is pumped gas composition, gas contains excluding condensable vapors, presence of dust particles, with or without corrosion, etc.Need to know when choosing a vacuum pump gas composition, gas is pumped to choose appropriate pump.If gas containing particle, and corrosive gas and vapor, should be considered in the pump inlet piping installation of auxiliary equipment, such as condenser, filter, etc.
7, vacuum pump oil steam discharged’s impact on the environment.If pollution is not permitted in the environment, can choose oil-free vacuum pump, or the oil steam exhaust to the outside.
8, vacuum pump vibration of work have influence to the process and the environment.If the process does not allow, should choose no vibration of the pump and adopt measures to prevent vibration.
9, The price of vacuum pump, operation and maintenance costs.