B722-01-880 Issue K
Page 24
© Edwards Limited 2007. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
Operation
4.3
Shut-down
Note:
In an emergency only, open the vent-valve quickly to decelerate the pump rotor in the shortest possible
time.
Use the procedure below to shut down a basic, manually-controlled pumping system with a manual vent-valve and
an EXC Controller. Refer to the EXC Controller instruction manual where the backing-pump and accessories are
automatically controlled by the EXC Controller.
1. Switch off the backing-pump and press the Start/Stop button on the EXC Controller to switch off the EXT pump.
2. When the EXT pump rotational speed has fallen to below 50% of full rotational speed, turn the manual
vent-valve anticlockwise to open it. Ensure that the rate of pressure rise does not exceed the allowed rate of
pressure rise, otherwise you can damage the pump: refer to
3. If water-cooling is in use, turn off the cooling-water supply.
4.4
Safety interlocks and control system
The pump protection and safety interlock features are listed below. Refer to the instruction manual supplied with
the EXC Controller for a full description of these features:
z
The EXC Controller monitors the temperature of the EXT pump and the electrical power consumption of the
pump. If the EXC Controller detects excessive power consumption or temperature, the rotational speed of
the pump motor is reduced until the power and temperature return to normal
z
If the rotational speed is reduced to 50% of nominal speed, then the pump is stopped immediately (or after a
user defined time delay) and the Fail LED on the EXC Controller lights
z
If pump rotational overspeed is detected by the EXC Controller, the pump is stopped immediately and the
FAIL LED on the EXC Controller lights.
If the Fail LED lights, switch off the backing-pump immediately and vent the EXT pump. Once the EXT pump has
stopped, rectify the cause of the failure (refer to
), press the EXC Controller Start/Stop button to reset
the Fail condition, and restart the EXT pump. If the pump is hot, allow sufficient time for it to cool before you restart
it.
4.5
Bakeout
CAUTION
When you bake the EXT pump to above 70
o
C at the inlet-flange, you must cool the pump by forced-air or water-
cooling, to prevent damage to the bearing lubricant.
If you heat your EXT pump (and your vacuum system), you will speed up the degassing process so that the pump will
reach ultimate vacuum in the shortest possible time. If you heat the pump, this will also prevent condensation of
vapours inside the pump.
You can use the Edwards BX bakeout band to heat the pump (refer to
). Fit the band around the pump,
just below the inlet-flange. When you bake the pump or the system, make sure that the temperature of the inlet-
flange does not exceed 100
o
C.
If you bake your vacuum system and the temperature of the system exceeds 200
o
C, you must put a radiation shield
between the system and the EXT pump. This radiation shield will reduce the heat radiated onto the pump rotor.
Typically, a bakeout of four hours is long enough to remove water condensation from the pump. However, the
bakeout time will depend on the amount of condensation in the pump and the vacuum system, and the ultimate
pressure you want to achieve.
Summary of Contents for EXT250 Series
Page 2: ......