4
OPERATION
WARNING
Do not disconnect the pump-to-controller cable while the EXT250M is operating. If you
do, there may be a risk of injury or death by electric shock, and the pump rotor will drop
onto its safety bearings which will cause unnecessary wear.
WARNING
Do not expose any part of your body to vacuum. If you do, you may be injured.
4.1
Start-up
CAUTION
Avoid sudden shocks and continuous heavy external vibration while the pump is
operating, as this may cause the pump rotor to repeatedly touch the safety bearings.
Use the procedure below to start up a basic, manually-controlled pumping system with an
EXC300M Controller. Refer to the EXC300M Controller instruction manual for simplified
procedures, where the backing-pump and accessories are automatically controlled by the
EXC300M Controller.
1.
Switch on the EXC300M Controller. The pump electromagnetic bearing will levitate the
rotor assembly.
2.
Turn the manual vent-valve clockwise to close it.
3.
Turn on the cooling-water supply (if water cooling is used).
4.
Start the backing-pump.
5.
When the vacuum system pressure is approximately 1 mbar (1 x 10
2
Pa) or less, press the
Start/Stop switch on the EXC300M Controller to start the EXT250M. The pump will then
accelerate to full operating speed.
The backing-pump and the EXT250M can be started simultaneously; this will allow the
EXT250M rotor to act as an effective baffle throughout the pump-down cycle. However, if the
volume of the vacuum chamber (together with the backing-pump) is more than approximately
25 litres, the time that the EXT250M takes to accelerate to half speed might cause the EXC300M
Controller to enter a ‘Fail’ condition. To adjust the time allowed for the EXT250M to accelerate to
half speed, refer to the instruction manual supplied with the EXC300M Controller.
Note:
The first time you pump down the system to vacuum, you must re-tighten the bolts which secure
the inlet-flange: refer to Section 3.3.4.
22
EXT250M Turbomolecular Pump
