Roots Vacuum Pumps
Roots pumps are rotary plunger type pumps where two symmetrically shaped impellors rotate in contrary directions inside the pump housing. Because of insufficient friction in suction chamber the roots vacuum pump is normally capable of operating at high speeds. The roots pumps operate at the high speeds definitely quietly due to insufficient reciprocating mass which also provides dependable dynamic balancing. As fore vacuum pumps can be utilized rotary vane, rotary piston, screw and liquid ring pumps. This types 
of combined pumps can be utilized in all fields where the rough, moderate vacuum and high pumping speeds are needed.
Roots pumps are dry-working vacuum pumps and may pump high 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 a suitable pre-vacuum pump. As pre-vacuum pumps can be used, for example:
Single-stage oil lubricated rotary vane vacuum pumps (accessible last pressure approx. 10-2 mbar a)
Two-stage essential 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 short evacuation moments closed volumes are to be evacuated or constantly big volume streams are to be charged. Where in fact the suction house of the pre-vacuum pumps begins to drop (e.g., by single-stage essential oil lubricated rotary vane pumps with approx. 10 mbar), a roots pump could be started up as a 2. Stage. The suction real estate of this roots pump can be up to 10 moments larger as the suction real estate of the pre-vacuum pump.
In a Roots vacuum pump, an inlet slot is located at a posture n Air Vacuum Pump china spaced by a positive displacement angle of 120° in one direction from a center of each rotational axis in accordance with an imaginary line m connecting rotor axes. An outlet slot is located at a position o contrary to the inlet slot relative to the line. An atmosphere feed interface is shaped at a posture t on a casing wall acquired by returning by 90° from the 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 port sides immediately after atmosphere suction respectively. The casing provides discharge grooves within an section of the inner wall so as to talk to the wall plug port. The area ranges from the positioning o to a position u obtained by returning by 45° from the position o to the inlet port side. The discharge grooves possess a total volume which range from 2% to 5% of a volume of one of the closed spaces.