Basic difference between single-stage rotary vane vacuum pump and double-stage rotary vane vacuum pump

The basic difference between the lubrication methods of a single-stage rotary vane vacuum pump and a two-stage rotary vane vacuum pump is that their applicable ranges are different. It is not so much that the two-stage rotary vane vacuum pump itself has the ability to generate a lower limit pressure, and it is better to say that the effective fractionation in the two-stage rotary vane vacuum pump makes it more suitable for working at low pressure (less than 1 Torr).
The pollution caused by oil decomposition eventually occurs in atmospheric-grade oils, and its effect on primary performance is not significant, which means that oil changes can be satisfactorily worked for a long time between oil changes. The use of gas cylinders helps to obtain the effect of purifying the oil. At the inlet of the pump, it only increases the partial pressure of air by a few thousandths of Torr, and at the same time reduces the operating noise. Even without a gas ballast, the noise level of a two-stage rotary vane vacuum pump is generally lower than that of a single-stage rotary vane vacuum pump. The hydraulic noise generated by the atmospheric-grade high oil flow rate does not exist at high vacuum levels. The low oil flow rate makes the two-stage rotary vane vacuum pump suitable for working under low pressure and is not suitable for continuous operation under high pressure.
For large gas mass flow, when the oil in the high vacuum class reservoir is depleted, the oil cannot be splashed back into the pump chamber in the face of strong air flow. Therefore, when it is necessary to continue working at a high pressure (about 10 Torr or more), the oil should be forcibly provided for lubrication.
The lubrication system of a single-stage rotary vane vacuum pump is based on the differential pressure principle, which works well at pressures below 500-600 Torr. When the inlet pressure is high, the gas recirculation in the oil circuit prevents the flow of oil, and only the mandatory oil supply can work continuously under a pressure of 500 Torr or more. When it is necessary to handle large mass denier flow rates, a single-stage rotary vane vacuum pump is generally considered to be equipped with an oil separator.

More vacuum pump information is available at China Vacuum Pump Trading Network (/).