Working principle of dry vacuum pump

Dry vacuum pump (also referred to as dry mechanical pump) refers to a mechanical vacuum pump that can start pumping from atmospheric pressure and directly discharge the pumped gas to the atmosphere. There is no oil or other working medium in the pump cavity, and the limit pressure of the pump is the same or close to that of the oil sealed vacuum pump.

The dry vacuum pump is a suction and exhaust equipment which uses a pair of screws to make synchronous and high-speed reverse rotation in the pump shell. The two screws are supported by bearings after fine dynamic balance correction and installed in the pump shell. There is a gap between the screws and the screws. Therefore, there is no friction between them during the operation of the pump. The operation is stable, the noise is low, and the working cavity does not need lubricating oil. Therefore, the The dry-type screw pump can pump out the gas containing a large amount of water vapor and a small amount of dust, with higher limit vacuum, lower power consumption, energy saving, maintenance free, etc. It is an updated product of oil seal / water ring / jet vacuum pump.

The scroll of oil-free scroll vacuum pump is a scroll like structure formed by one or several involute helices connected with a plane at one end. A pair of scroll plates, composed of a static scroll plate and a dynamic scroll plate, constitute the basic suction mechanism of a vortex oil-free vacuum. For example, in a two-stage scroll oil-free vacuum pump, there are two fixed vortices with corresponding directions, and one rotating one between the two vortices. The dynamic and static vortices move relative to each other to form a crescent shaped real cavity with constant volume change, which enables the air to be sucked in from the suction port and discharged from the exhaust port, thus completing the exhaust cycle.

The limit vacuum degree of dry screw vacuum pump, claw vacuum pump and oil-free scroll vacuum pump is very high, and the high limit vacuum can reach 1-2pa; the oil-free reciprocating vacuum pump is a coarse vacuum equipment, and the limit vacuum degree is low, so it needs to be combined with roots vacuum pump to improve the limit vacuum. Air extraction: due to internal structure problems, the oil-free scroll vacuum pump has small air extraction, which is only applicable to the process of small air extraction; the dry screw vacuum pump has complete models, which can be applied to the process of large air extraction, and can meet the needs of different customers with the help of roots vacuum pump. Stability: the dry screw vacuum pump has stable performance, low noise and low failure rate; the oil-free reciprocating vacuum pump has simple structure and high noise, which requires frequent replacement of slide. Due to the complex assembly of claw vacuum pump, the rotor and the shaft are not integrated. In case of failure, it is necessary to disassemble and assemble all the parts again and again, so as to reduce the product performance and stability.

Due to the flammable, explosive and corrosive gases in the process gas of chemical industry and pharmaceutical industry, the dry vacuum pump needs special treatment. The internal structure of dry screw vacuum pump is simple, two rotors and pump cavity can be treated with anti-corrosion treatment, and two kinds of coating, nickel phosphorus coating and Teflon coating, can be selected. It is difficult to do anti-corrosion treatment for claw vacuum pump, almost no surface treatment can be done between all stages of diaphragm, and the anti-corrosion coating on the rotor surface is easy to be damaged during assembly. The oil-free scroll vacuum pump is only suitable for pumping clean gas, and it can't pump inflammable, explosive and corrosive gas.

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