Description
12
GA03108_002_C1 - 04/2018 - © Leybold
In impeller positions I and II, the volume in the intake flange is increased.
When the impellers rotate further to position III, part of the volume is sealed
off from the intake side.
In position IV, this volume is opened to the discharge side, and gas at
backing pressure (higher than the intake pressure) flows in. The inflowing gas
compresses the gas volume pumped from the intake side. As the impellers
rotate further, the compressed gas is ejected via the discharge flange. This
process occurs twice per complete revolution of each of the two impellers.
Due to the non-contacting rotation in the pumping chamber, Roots pumps
can be operated at high speeds (standard n = 3,000 rpm at a mains
frequency of 50 Hz). Thus a relatively high pumping speed is attained with
small pumps.
The pressure differential and compression ratio between the intake and
discharge sides are limited on Roots pumps. If the allowable pressure
differential is exceeded, the pump overheats.
Fig. 1.3 Longitudinal section of a RUVAC WS 1001 (horizontal flow)
1 Gearwheels
8 Fan cowl
2 Bearings
9 Fan
3 Impeller seals
10 Drive shaft
4 Impellers
11 Centrifugal disc lubricator
5 Driven impeller shaft
12 Equalisation passage
6 Stator
13 Intake port
7 Can
14 Centrifugal disc lubricator
