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 normally capable of working at high speeds. The roots pumps operate at the high speeds certainly 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 combined pumps can be utilized in all fields where the rough, medium vacuum and high pumping speeds are required.
Roots pumps are dry-working 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 just in combination with the right pre-vacuum pump. As pre-vacuum pumps can be used, for example:
Single-stage oil lubricated rotary vane vacuum pumps (Air Vacuum Pump china 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 last pressure approx. 1 mbar a).
Roots pumps, in mixture with suitable pre-vacuum pumps, are used in particular when in a nutshell evacuation moments closed volumes are to be evacuated or constantly big quantity streams are to 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 switched on as a 2. Stage. The suction property of this roots pump could be up to 10 occasions larger as the suction property of the pre-vacuum pump.
In a Roots vacuum pump, an inlet port is located at a position n spaced by a positive displacement angle of 120° in one direction from a center of each rotational axis relative to an imaginary line m connecting rotor axes. An outlet slot is located at a posture o reverse to the inlet port in accordance with the line. An atmosphere feed port is shaped at a posture t on a casing wall attained 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 port sides immediately after air flow suction respectively. The casing offers discharge grooves within an area of the inner wall structure so as to talk to the wall plug port. The region ranges from the position o to a position u attained by returning by 45° from the positioning o to the inlet port aspect. The discharge grooves have a total volume ranging from 2% to 5% of a level of among the closed spaces.