In addition to the main characteristics, limiting pressure, flow rate and pumping rate of vacuum pump, there are also some special terms to describe the relevant performance and parameters of the pump.

1. Start up pressure. The pressure when the pump operates without damage and has pumping function.

2. Front stage pressure. The outlet pressure of vacuum pump whose discharge pressure is lower than 101325pa.

3. Maximum working pressure. The inlet pressure corresponding to the maximum flow. Under this pressure, the pump can operate continuously without deterioration or damage.

4. Maximum pre stage pressure. Exceed the pre stage pressure that can damage the pump.

5. He coefficient. The ratio of the actual pumping rate on the area of the pumping channel to the theoretical pumping rate calculated according to the molecular flow.

6. Compression ratio. The ratio of the pump's outlet pressure to the pump's inlet pressure for a given gas.

7. Return flow rate. The mass flow rate of pump fluid per unit area and per unit time passing through the pump inlet opposite to the pumping direction when the pump is operating under specified conditions.

8. Pumping coefficient. The ratio of the actual pumping rate of the pump to the theoretical pumping rate of the pump inlet area calculated according to the molecular flow.

9. The allowable amount of water vapor (unit: kg / h) is the mass flow rate of water vapor that can be pumped out by pneumatic pump under normal environmental conditions.

10. Maximum allowable steam inlet pressure. Under normal circumstances, the maximum inlet pressure of water vapor that can be removed by pneumatic pump during continuous operation.