3 Operation
3.1 General operation rules
The magnetic bearing in the MAG are immune to wear.
In addition to the magnetic bearings, the MAG is equip-
ped with touch-down bearings which protect the rotor
against mechanical contact with the stator if the pump is
subjected to external shock loading or when the pump is
switched off. These touch-down bearings have a limited
service life. Please observe the following in order to
obtain maximum service life.
•
Avoid shock and vibrations when the pump is run-
ning. Shocks perpendicular to the rotation axis are
particularly harmful. If the pump appears to be run-
ning in the mechanical bearings continuously it is
switched off.
•
Do not suddenly expose the MAG to an already eva-
cuated vacuum chamber. The pressure surge may
cause the rotor to make contact with the touch-down
bearings. This will cause increased wear.
•
Do not disconnect the MAG and MAG.DRIVE
digital
while they are operating. If MAG and MAG.DRIVE
di-
gital
have been disconnected accidently re-connect
them.
•
Do not stop the MAG with the mains. Use the STOP
key or a stop command. Switching off the mains while
the pump is running will wear out the touch down
bearings.
The pump may make noise during the run-up and run-
down phases. This has neither an influence on the pump
nor on the process.
Warning
Monitor the purge gas supply continuously.
Insufficient purge gas flow can result in:
• Process gases entering the motor and
bearing area of the MAG
• Process gases escaping from the purge
gas inlet
• Humidity entering the pump.
Refer to Section 2.7.
Warning
The pump will be hot during operation. Burn
hazard!
Venting
As to suitable gases, see Chapter 2.7.
Venting Method
The pump must be vented via the purge gas and ven-
ting valve or the vent port when shutting the pump
down.
When additionally venting the vacuum chamber, the ven-
ting function of the purge gas and venting valve must be
opened before opening the chamber valve. This will
ensure the presence of a higher pressure in the magne-
tic bearings compared to the remaining vacuum area.
This will prevent particles, dust or aggressive gases from
being forced into the not yet vented motor chamber of
the pump.
Speed of the pressure rise
All turbomolecular pumps may be vented at full speed.
However, the pressure must not increase faster than
specified through the pressure rise curve.
The pump must be vented significantly slower when
there is the risk of particles entering into the pump from
the process. During venting, the flow must be of the
laminar type in both the vacuum chamber and the turbo-
molecular pump.
The pump must not be vented to pressures above
atmospheric pressure.
Operation
48
GA 05.141/6.02 - 07/2003
