What is the principle behind a vacuum pump?

The function of a vacuum pump is to technically generate a vacuum. The first functional vacuum pump was built by Otto von Guericke in 1649, it was a piston pump.

A distinction is made between vacuum pumps either according to their technical function or according to the vacuum they generate. From a technical point of view, a vacuum pump is a compressor and not a pump in the strict sense.

Basic principle of vacuum pump

Basically, vacuum pumps are divided into gas-binding vacuum pumps and gas transfer vacuum pumps according to their physical operating principle.

Gas binding vacuum pump

A gas-binding vacuum pump uses the principle of sorption for its pumping action, in which particles are bound on the surface of a solid. This reduces the pressure in the recipient. Types of gas-binding vacuum pumps include adsorption pumps, getter pumps and cryopumps.

Gas transfer vacuum pumps

In the case of gas transfer vacuum pumps, the particles are transported either through the transmission of an impulse, for example through impacts, or in the case of positive displacement vacuum pumps in a closed working space. These types of construction require either laminar or molecular flow to function. Classic representatives are z. B. Roots pumps, liquid jet pumps, reciprocating piston vacuum pumps, diaphragm pumps, (turbo) molecular pumps, rotary vane pumps. Screw vacuum pumps and rotary vane pumps.

Symbol for vacuum pumps for the pneumatic plan:

The different designs are used for different purposes. For the generation of low vacuum pressures of p <10-3 mbar two pump stages are required. To do this, a first vacuum pump (the so-called backing pump) generates a backing vacuum (for example with a rotary slide pump), and the next vacuum pump is then connected to the actual recipient. A typical combination of vacuum pumps is e.g. B. is a positive displacement pump as a backing pump in combination with a turbo-molecular vacuum pump.
The compression of the air reduces its volume, so several pumps of the second stage can be supplied by a single backing pump via a tube system in which there is a laminar flow. Safety mechanisms such as automatic valves, tanks and pressure gauges ensure operational safety and allow breaks for the backing pump.

Types of vacuum pumps

The following is a list of different types of vacuum pumps:

  • Turbo molecular pump (TMP)
  • Sorption pump
  • Jet pump
  • Positive displacement pump
  • Molecular pump
  • Cryopump
  • Gate valve pump

Propellant or jet pumps use either the friction of the laminar flow, respectively. ensure turbulence that increases friction or take advantage of the fact that molecular flows can penetrate unhindered.

In the case of positive displacement pumps, for economic reasons (manufacturing and operating costs) as well as with regard to reliability in certain designs, variants that use the molecular flow for sealing between stator and rotor have become established. These achieve higher speeds compared to other positive displacement pumps.

Turbines with laminar flow are used, for example, as spiro pumps in vacuum technology or are used to suck air out of a housing (e.g. PC housing). Due to the higher suction power, the molecular variant is mainly used in the vacuum area.