GA05141_0702 - 09/2004
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Installation
2.4 Connecting the backing pump
A two stage rotary vane pump or dry-compression backing pump is requi-
red to support operation of the MAG.
In case of high gas throughput, it may also be necessary to use a roots blo-
wer to achieve the backing pressure necessary for operating the MAG.
Fig. 34 shows schematically the design of a pump system incorporating a
MAG with an additional foreline valve and an isolation valve between cham-
ber and MAG.
The foreline isolation valve is recommended to protect the MAG from shock
venting in case of uncontrolled shut down of the backing pump. This valve
must be able to close fast enough to avoid pressure increase in the MAG.
In case of an oil-sealed backing pump the foreline isolation valve protects
the MAG from backstreaming oil vapor during standstill.
Connect the forevacuum flange of the MAG to the backing pump.
The torque on the forevacuum connection flange must not exceed the
values shown in Fig. 35.
Fig. 34 Layout of a turbomolecular pump system
1Turbomolecular pump
2 Forevacuum gauge point
3 Backing pump
4 Anti-vibration bellows
5 Forevacuum valve
6 High vacuum valve
7 Purge gas connection
8Valve in the roughing line
9 Electronic frequency converter
— — — — roughing line; recommended
if shorter cycle times are to be achieved
— · — · — · — · DRIVE/BEARING and TMS cable
Foreline valve
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