Roots Vacuum Pumps
Roots pumps are rotary plunger type pumps where two symmetrically shaped impellors rotate in contrary directions in the pump housing. Because of lack of friction in suction chamber the roots vacuum pump is capable of operating at high speeds. The roots pumps operate at the high Air Vacuum Pump china speeds absolutely quietly due to lack of reciprocating mass which also provides reliable dynamic balancing. As fore vacuum pumps can be utilized 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-running vacuum pumps and may pump large volumes. In blower operation 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 final 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 final pressure approx. 1 mbar a).
Roots pumps, in combination with suitable pre-vacuum pumps, are used in particular when in short evacuation situations closed volumes are to be evacuated or constantly big quantity streams should be charged. Where the suction property 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 could be started up as a 2. Stage. The suction real estate of the roots pump could be up to 10 instances larger as the suction property 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 port is located at a posture o contrary to the inlet interface relative to the line. An air feed slot is produced at a position t on a casing wall obtained by returning by 90° from the position o to the inlet interface side to ensure that two closed spaces are defined by adjacent rotor lobes and a casing inner wall at both interface sides immediately after atmosphere suction respectively. The casing has discharge grooves in an section of the inner wall so as to communicate with the store 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 level of among the closed spaces.