Roots Vacuum Pumps
Roots pumps are rotary plunger type pumps where two symmetrically shaped impellors rotate in contrary directions in the pump housing. Due to lack of friction in suction chamber the roots vacuum pump is normally capable of working at high speeds. The roots pumps operate at the high speeds completely quietly due to insufficient reciprocating mass which also provides reliable powerful balancing. As fore vacuum pumps can be used rotary vane, rotary piston, screw and liquid band pumps. This types of mixed pumps can be used in all fields where the rough, moderate vacuum and high pumping speeds are required.
Roots pumps are dry-working vacuum pumps and may pump large volumes. In blower procedure you can reach vacuum to 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 only in combination with the right pre-vacuum pump. As pre-vacuum pumps may be used, for example:
Single-stage oil lubricated rotary vane vacuum pumps (accessible last pressure approx. 10-2 mbar a)
Two-stage oil lubricated rotary vane vacuum pumps (accessible last pressure approx. 10-3 mbar a)
Liquid ring vacuum pumps, if necessary in mixture with ejectors (accessible final pressure approx. 1 mbar a).
Roots pumps, in combination with suitable pre-vacuum pumps, are found in particular when in short evacuation occasions closed volumes should be evacuated or constantly big quantity streams are to be charged. Where the suction property of the pre-vacuum pumps begins to drop (e.g., by single-stage oil lubricated rotary vane pumps with approx. 10 mbar), a roots pump could be switched on as a 2. Stage. The suction house of the roots pump can be up to 
10 times bigger as the suction home of the pre-vacuum pump.
In a Roots vacuum pump, an inlet interface is located at a position n spaced by a positive displacement angle of 120° in a single direction from a center of every rotational axis in accordance with an imaginary line m connecting rotor axes. An outlet interface is located at a position o reverse to the inlet slot relative to the line. An air flow feed port is shaped at a posture t on a casing wall structure acquired by returning by 90° from the Air Vacuum Pump china positioning o to the inlet port side so that two closed areas are defined by adjacent rotor lobes and a casing internal wall at both interface sides immediately after air flow suction respectively. The casing offers discharge grooves within an area of the inner wall so as to talk to the store port. The area ranges from the positioning o to a position u obtained by returning by 45° from the positioning o to the inlet port side. The discharge grooves possess a total volume ranging from 2% to 5% of a volume of among the closed spaces.