What Is The Working Principle Of A Mechanical Pump
Jul 20, 2025
The commonly used mechanical pumps include fixed plate type, rotary plate type, and slide valve type, with the most commonly used being rotary plate vacuum pump (referred to as rotary plate pump), which is an oil sealed mechanical vacuum pump. Rotary vane mechanical pumps can be used independently or as pre pumping pumps for other high vacuum pumps or ultra-high vacuum pumps. It can be used to remove dry gases from vacuum sealed containers, and with a gas damper installed, it can also remove a certain amount of condensable gases. But it is not suitable for extracting gases with high oxygen content, particulate dust, and chemical reactions to pump oil that are corrosive to metals. Rotary vane mechanical pump is one of the most basic vacuum equipment in vacuum technology.
Rotary vane mechanical pumps are mostly small and medium-sized pumps, which have two types: single-stage pumps and two-stage pumps. A two-stage pump is a structure that connects two single-stage pumps in series. The difference between single-stage and two-stage pumps is that two-stage pumps can achieve higher vacuum levels.
In a two-stage pump, when there are unequal chambers between the low vacuum stage and the high vacuum stage, an auxiliary exhaust valve needs to be installed. The purpose of setting up an auxiliary exhaust valve is to start working when the gas compressed by the high vacuum stage reaches the exhaust pressure when the inlet pressure is high, and some gas is discharged from it, while the remaining gas is drawn away by the low vacuum stage. When the inlet pressure of the mechanical pump decreases, the exhaust volume of the auxiliary exhaust valve will also decrease, eventually reaching closure. During the entire pumping process, when the partial pressure of condensable gas exceeds the pump temperature and reaches the saturation vapor pressure, the condensable gas will condense and mix with the pump oil. With the operation of the pump and the circulation of the pump oil, it will re evaporate into vapor when returning to the high vacuum end. It will affect the pumping performance of the pump and exacerbate pump oil pollution.
Setting up a gas ballast valve can effectively prevent the condensation of condensable gases. During the compression process of the pump, the gas ballast valve mixes permanent dry gas into the compressed gas through the gas ballast hole. Before the partial pressure of condensable gas reaches the saturated vapor pressure at pump temperature, the compressed gas pressure can reach the exhaust pressure. Open the exhaust valve to discharge both condensable and dry gases simultaneously. Under normal circumstances, oil sealed mechanical pumps are equipped with pneumatic valves, and their use can be found in the technical manual of the oil sealed mechanical vacuum pump. The disadvantage of this pump is that it is easy to return oil and spray oil. To overcome these disadvantages, the manufacturer also provides accessories such as molecular sieves, oil mist collectors, dust filters, and oil filters.