© Edwards Limited 2008. All rights reserved.
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Introduction
A313-01-880 Issue A
1.3
Principle of operation
The HV series of positive displacement vacuum booster pumps follow the well established principles of the “Roots”
type machine. Operation is both simple and effective. Two rotors with identical profiles rotate in opposite directions
within a casing (refer to
).
The shape of the rotor is such that a small accurately gauged clearance is maintained at all times between the rotors,
and between the tips of the rotors and the bore of the casing. As they rotate, the gas is drawn into the space between
the rotor and the casing, where it is trapped when the tip of the rotor passes the edge of the inlet port. Continuing
its rotation, the opposite tip of the rotor passes the edge of the outlet port and trapped gas is pushed out into the
discharge pipework. This action is repeated twice for each revolution of the rotor and, therefore, four times for each
revolution of the drive shaft.
Figure 1 - Operating principles
