First, the performance parameters of the vacuum pump 1, the ultimate pressure of the pump The ultimate pressure unit of the pump is Pa, is the pump at the entrance with a standard test cover and work under the conditions specified, without the introduction of normal gas work tends to be stable The lowest pressure. 2, the pumping speed of the pump Pump pumping speed unit is m3 / s or l / s, is the pump equipped with a standard test cover, and work in accordance with the provisions of the conditions, the gas flow from the test cover and the test cover The ratio of the equilibrium pressure measured at the specified location. Pump pumping speed. 3, the amount of vacuum pump vacuum pump vacuum pump unit is Pam3 / s or Pal / s. It refers to the pump inlet gas flow. 4, the starting pressure of the vacuum pump Vacuum pump starting pressure unit is Pa, it refers to the pump start without damage and the pressure when pumping. 5, the pump before the pressure The vacuum pump's preceding pressure unit is Pa, it refers to the discharge pressure is lower than one atmosphere of the vacuum pump outlet pressure. 6, the maximum pressure before the vacuum pump The maximum pressure in front of the vacuum pump unit pressure unit is Pa, which means more than the previous pressure can damage the pump. 7, the maximum working pressure of the vacuum pump The maximum working pressure of the vacuum pump unit is Pa, which refers to the maximum intake pressure corresponding to the inlet pressure. Under this pressure, the pump can work continuously without deterioration or damage. 8, compression ratio Compression ratio is the pump outlet pressure for a given gas inlet pressure ratio. 9, Ho coefficient Pump pumping area on the actual pumping speed and molecular effusion calculated by the ratio of the theoretical pumping speed. 10, the pumping speed coefficient The actual pumping speed of the pump inlet by molecular diarrhea calculated theoretical pumping speed ratio. 11, the return flow rate of the pump unit is g / cm2.s. It refers to the pump when the required conditions work, through the pump inlet unit area pump flow mass flow rate. 12, the allowable amount of water vapor The allowable amount of water vapor is kg / h, it refers to the pump under normal environmental conditions, gas pump can be removed in continuous operation of the water vapor mass flow. 13, the maximum allowable water vapor inlet pressure Maximum allowable water vapor inlet pressure unit is Pa. It refers to the maximum inlet pressure of water vapor that can be extracted by the gas-operated pump under continuous operation under normal environmental conditions. Second, the use of vacuum pump As a result of a variety of vacuum pumps have a working pressure range and starting pressure are different, so the choice of vacuum pump must meet these requirements. Table 3-1 shows the operating pressure range of various commonly used vacuum pumps and pump starting pressure values ​​for reference. 8, compression ratio Compression ratio is the pump outlet pressure for a given gas inlet pressure ratio. 9, Ho coefficient Pump pumping area on the actual pumping speed and molecular effusion calculated by the ratio of the theoretical pumping speed. 10, the pumping speed coefficient The actual pumping speed of the pump inlet by molecular diarrhea calculated theoretical pumping speed ratio. 11, the return flow rate of the pump unit is g / cm2.s. It refers to the pump when the required conditions work, through the pump inlet unit area pump flow mass flow rate. 12, the allowable amount of water vapor The allowable amount of water vapor is kg / h, it refers to the pump under normal environmental conditions, gas pump can be removed in continuous operation of the water vapor mass flow. 13, the maximum allowable water vapor inlet pressure Maximum allowable water vapor inlet pressure unit is Pa. It refers to the maximum inlet pressure of water vapor that can be extracted by the gas-operated pump under continuous operation under normal environmental conditions. Second, the use of vacuum pump As a result of a variety of vacuum pumps have a working pressure range and starting pressure are different, so the choice of vacuum pump must meet these requirements. Table 3-1 shows the operating pressure range of various commonly used vacuum pumps and pump starting pressure values ​​for reference.