Maintenance
35
7.7
Set/adjust the silencer
If the silencer is not functioning, a knocking noise becomes audible at final vacuum. This
does not damage the pump, although can have a negative affect at the installation loca-
tion.
The silencer is set using a standard screwdriver when the pump is running at operating
temperature and vacuum flange and gas ballast valve are closed.
Close needle valve 100/111 and wait until you hear oil hammer.
Untwist needle 100/111 until the oil hammer noise disappears (approx. 1/2 rotation).
Hold needle valve 100/111 in position with the screwdriver and tighten fixing nut 101.
If the silencer is set correctly, the pump vacuum has a total pressure of
< 6.0
10
-2
hPa.
