Roots Vacuum Pumps
Roots pumps are rotary plunger type pumps where two symmetrically shaped impellors rotate in reverse directions inside the pump housing. Because of insufficient friction in suction chamber the roots vacuum pump is capable of operating at high speeds. The roots pumps operate at the high speeds completely quietly due to insufficient reciprocating mass which also provides dependable dynamic balancing. As fore vacuum pumps can be used rotary vane, rotary piston, screw and liquid ring pumps. This types of mixed pumps can be utilized in all fields where the rough, medium vacuum and high pumping speeds are needed.
Roots pumps are dry-running vacuum pumps and may pump high volumes. In blower operation you can reach vacuum to Air Vacuum Pump china approx. 0.5 bar a (as a single aggregate). In the execution as a high-vacuum blower vacuums are reached up to 10-3 mbar a, but just in combination with a suitable pre-vacuum pump. As pre-vacuum pumps can be used, for example:
Single-stage essential oil lubricated rotary vane vacuum pumps (accessible last pressure approx. 10-2 mbar a)
Two-stage essential oil lubricated rotary vane vacuum pumps (accessible final pressure approx. 10-3 mbar a)
Liquid ring vacuum pumps, if necessary in mixture with ejectors (accessible last pressure approx. 1 mbar a).
Roots pumps, in mixture with suitable pre-vacuum pumps, are used in particular when in a nutshell evacuation situations closed volumes are to be evacuated or constantly big quantity streams should be charged. Where the suction house of the pre-vacuum pumps starts to drop (e.g., by single-stage essential oil lubricated rotary vane pumps with approx. 10 mbar), a roots pump can be switched on as a 2. Stage. The suction property of the roots pump can be up to 10 times bigger as the suction house of the pre-vacuum pump.
In a Roots vacuum pump, an inlet port is located at a posture n spaced by a positive displacement angle of 120° in a single direction from a center of each rotational axis relative to an imaginary line m connecting rotor axes. An outlet interface is located at a posture o opposite to the inlet slot in accordance with the line. An air feed port is created at a position t 
on a casing wall structure obtained by returning by 90° from the position o to the inlet port side so that two closed spaces are described by adjacent rotor lobes and a casing inner wall at both slot sides immediately after surroundings suction respectively. The casing has discharge grooves in an section of the inner wall structure so as to talk to the wall plug port. The region ranges from the positioning o to a posture u acquired by returning by 45° from the positioning o to the inlet port side. The discharge grooves have a total volume ranging from 2% to 5% of a level of among the closed spaces.