Vacuum pump selection: _ vacuum pump suction capacity calculation

a lot of people in the vacuum pump selection have to calculate the extraction capacity of vacuum pump, so the vacuum pump suction ability how to calculate? Today is to introduce a we commonly used calculation formula.

= 2。 303V/tLog( P1/P2) Among them: for the vacuum pump suction rate (S L/s) V for vacuum chamber volume ( L） T to reach for the vacuum degree required by the time ( s) P1 for initial vacuum degree, Torr) The P2 for vacuum degree ( Torr) For example: V = 500 l t = 30 S P1 = 760 torr P2 = 50 torr is: S = 2. 303V/t Log( P1/P2) = 2. 303x500/30xLog( 760/50) = 35. 4 l/s

vacuum pump suction capacity calculation finally to how do we select the vacuum pump model.

( 1) Occurring in the process of vacuum pump running vibration has no effect on the process and the environment. If the process is not allowed, please choose no vibration pump or vibration control measures.

( 2) Understand by pumping gas composition, gas excluding condensable vapors, whether there are particles of dust, corrosive. Choosing a vacuum pump, you need to know the gas composition and select suitable pumping gas pump. If the steam is contained in the gas, particles and corrosive gas, please consider condenser installed in the pump inlet pipe, dust collector and other auxiliary equipment.

( 3) Under the working pressure, vacuum water pump should be able to remove all gas produced in the process of vacuum equipment.

( 4) The right combination vacuum pump. Due to the selective pumping vacuum pump, sometimes can not meet the requirement of the pump, pump and multiple water pump combinations are needed to complement each other in order to meet the pumping requirements. For example, titanium sublimation pump for hydrogen gas with high pumping speed, but it can't pump and three pole sputtering ion pump ( Or double was asymmetrical cathode sputtering ion pump) The argon pumping speed. Combined, vacuum unit will have a better vacuum. In addition, some of the vacuum pump can't work under atmospheric pressure, to a vacuum; Some vacuum pump outlet pressure is lower than the atmospheric pressure, need backing pump, so you need to pump together.

( 5) The vacuum equipment of oil demand. If equipment strict with oil free, should choose a variety of oil pump, such as water ring pump, molecular sieve adsorption pump, sputter ion pump, cryogenic pump, etc. If not strict, you can choose to have an oil pump, add some oil measures, such as add cold trap, baffle, the oil well, etc. , can also meet the requirements of clean vacuum.

( 6) Correct selection of vacuum pump working point. Each pump has a certain working pressure range, such as: 2 bv series water ring vacuum pump working pressure range 760 MMHG ~ 25 MMHG ( Absolute pressure) , in such a wide range of pressure and pump suction speed changing with pressure, See see situation of pump) ) Performance curve) , its stable working pressure range is 760 ~ 60 MMHG. Therefore, we should choose the pump working point in this scope, are not allowed to work long time under 25 ~ 30 MMHG.

( 7) From the vacuum pump discharge of oil vapor how to affect the environment? If you don't allow pollution environment, you can choose oil-free vacuum pump or the oil vapor emission outside.

( 8) Vacuum pump working pressure should satisfy the limit of vacuum equipment vacuum and work pressure requirements. For example, if you need 10 MMHG work vacuum, vacuum drying process, the vacuum degree of vacuum pump should be selected for at least 2 MMHG, select up to 1 MMHG. The limit of the water pump vacuum often choose for half of the order of magnitude higher than vacuum vacuum equipment.

( 9) The price of the vacuum pump, operation and maintenance costs.