Many customers are not very clear about the classification of vacuum pumps. Those who have used vacuum pumps before may know which type they want to choose, however, it is very difficult for users who purchase vacuum pumps for the first time to decide use which kind of pump because they search for vacuum pumps on the Internet. There will be many strange articles that make customers feel like looking at flowers in a fog, but after all, they don’t understand it so thoroughly.
Generally speaking, vacuum pumps are divided into three categories, namely, water-filled vacuum pumps, oil-filled vacuum pumps and oil-free vacuum pumps.
1. A water-filled vacuum pump refers to a water-ring vacuum pump, which uses water as a working fluid to achieve suction, compression and exhaust by changing the volume of the pump chamber to achieve the purpose of vacuum extraction. This pump can pump water vapor and corrosive gas, its type cantilever water ring vacuum pump, 2BV water ring vacuum pump, 2BE water ring vacuum pump, 2SK water ring vacuum pump, etc.;
2. The oil-filledvacuum pump refers to the rotary vane vacuum pump. The gap between the rotary vane and the pump cavity is sealed with oil. The vacuum degree is much higher than that of the water ring vacuum pump, but water vapor and corrosive gases are not allowed to be pumped by oil-filled vacuum pump.
3. Oil-free vacuum pumps are often used in a clean environment and will not pollute the products produced.
Common vacuum pumps of working pressure range and starting pressure
Vacuum pump type Working pressure range (Pa) Starting pressure (Pa)
Slide valve vacuum pump 1×105～1.3×102 1×105
Rotary vane vacuum pump 1×105—6.7×10-1 1×105
Water ring vacuum pump 1×105—2.7×103 1×105
Roots vacuum pump 1.3×103—1.3 1.3×103
Turbo molecular pump 1.3—1.3×10-5 1.3
Steam jet pump 1×105—1.3×10-1 1×105
Oil diffusion pump 1.3×10-2—1.3×10-7 1.3×10
Oil vapor jet pump 1.3×10—1.3×10-2
Vacuum pump parameter name
1. The ultimate pressure of the vacuum pump
The ultimate pressure unit of the pump is Pa, which means that the pump is equipped with a standard test cover at the entrance and works under the specified conditions, and it tends to stabilize the lowest pressure under the condition of normal operation without introducing gas.
2. The pumping rate of the vacuum pump
The pumping rate unit of the pump is m3/s or l/s, which means that when the pump is equipped with a standard test cover and works under specified conditions, the gas flow through the test cover and the equilibrium pressure measured at the specified position of the test cover. The ratio is referred to as the pumping speed of the pump.
3. The pumping capacity of the vacuum pump
The pumping unit of the vacuum pump is Pa m3/s or Pa l/s. It refers to the gas flow at the inlet of the pump.
4. Starting pressure of the vacuum pump
The starting pressure unit of the vacuum pump is Pa, which refers to the pressure when the pump starts without damage and has a pumping effect.
5. The front pressure of the pump
The front pressure unit of the vacuum pump is Pa, which refers to the outlet pressure of the vacuum pump whose exhaust pressure is lower than atmosphere.
6.The maximum fore pressure of the vacuum pump
The maximum fore-stage pressure unit of the vacuum pump port is Pa, which means that the fore-stage pressure that can damage the pump is exceeded.
7. The maximum working pressure of the vacuum pump
The maximum working pressure unit of the vacuum pump is Pa, which refers to the inlet pressure corresponding to the maximum pumping volume. Under this pressure, the pump can work continuously without deterioration or damage.
8. Compression ratio
Compression ratio refers to the ratio of the pump’s outlet pressure to the inlet pressure of a given gas.
9. Ho’s coefficient
The ratio of the actual pumping speed on the area of the pumping passage to the theoretical pumping speed calculated by the molecular effusion.
10. Pumping speed coefficient
The ratio of the actual pumping speed of the pump to the theoretical pumping speed calculated by the molecular effusion at the pump inlet.
11. Reflux rate
The unit of the pump’s reflux rate is g/cm2.s. It refers to the mass flow rate of the pump flow through the unit area of the pump inlet when the pump is working under the specified conditions.
12. Allowable amount of water vapor
The allowable unit of water vapor is kg/h, which refers to the mass flow of water vapor that the gas ballast pump can extract under normal environmental conditions.
13. The maximum allowable water vapor inlet pressure
The maximum allowable water vapor inlet pressure unit is Pa. It refers to the highest inlet pressure of water vapor that can be removed by the gas ballast pump during continuous operation under normal environmental conditions.
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