Roots Vacuum Pumps
Roots pumps are rotary plunger type pumps where two symmetrically shaped impellors rotate in reverse directions within the pump housing. Because of insufficient friction in suction chamber the roots vacuum pump can be capable of operating at high speeds. The roots pumps operate at the high speeds completely quietly due to lack of 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, moderate vacuum 
and high pumping speeds are required.
Roots pumps are dry-working vacuum pumps and will pump large volumes. In blower procedure you can reach vacuum to approx. 0.5 bar a (as an individual aggregate). In the execution as a high-vacuum blower vacuums are reached up to 10-3 mbar a, but just in combination with the right pre-vacuum pump. As pre-vacuum pumps may be used, for example:
Single-stage essential oil Air Vacuum Pump china 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 combination with ejectors (accessible last pressure approx. 1 mbar a).
Roots pumps, in combination with suitable pre-vacuum pumps, are found in particular when in a nutshell evacuation instances closed volumes are to be evacuated or constantly big quantity streams are to be charged. Where the suction real estate of the pre-vacuum pumps starts to drop (e.g., by single-stage oil lubricated rotary vane pumps with approx. 10 mbar), a roots pump can be switched on as a 2. Stage. The suction real estate of the roots pump can be up to 10 instances larger as the suction house 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 one 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 port relative to the line. An air flow feed port is produced at a position t on a casing wall structure obtained by returning by 90° from the positioning o to the inlet port side so that two closed spaces are defined by adjacent rotor lobes and a casing internal wall at both port sides immediately after surroundings suction respectively. The casing offers discharge grooves in an area of the inner wall structure so as to communicate with the outlet port. The region ranges from the positioning o to a position u acquired by returning by 45° from the position o to the inlet port aspect. The discharge grooves have a total volume which range from 2% to 5% of a volume of one of the closed spaces.