© Edwards Limited 2007. All rights reserved.
Page 27
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Maintenance
B722-01-880 Issue K
The EXC Controller trips into
Fail after 50% speed has been
reached - the first two speed
LEDs are lit.
Is the pressure too high?
If so, reduce the pumping load or check for a gross
leak into the system.
If the high gas load is temporary, configure the
EXC Controller to delay the Fail trip on 50% speed
and set an appropriate delay time (refer to the
instruction manual supplied with the
EXC Controller).
Is the EXT pump running too
hot?
Increase the cooling-water flow or decrease the
water temperature or do both. You may need to
change from air-cooling to water-cooling.
Does the EXT pump rotor
rotate freely?
If not, the EXT pump-bearings are damaged. Consult
Edwards or your supplier.
The EXC Controller trips into
Fail - all the speed LEDs are
lit.
-
Consult Edwards or your supplier.
Ultimate pressure cannot be
reached.
Is the pressure limited by
water vapour?
Bake the system and pump.
Are any of the vacuum
gauges contaminated?
If so, clean or replace them.
Is the pumping speed
insufficient (due to poor
conductance between the
pump and the gauge or too
large a chamber)?
Increase the conductance or reduce the volume.
Is the backing pressure
< 0.2 mbar (20 Pa)?
If not, check for backing line leaks. If the
throughput is high, you may need a larger backing-
pump.
Is the high-vacuum area of
the system contaminated?
If so, clean the high-vacuum system.
Check the rest of your
system for leaks and
contamination.
If found, clean the contaminated areas and repair
the leaks.
Remove the pump from the
system and test the ultimate
pressure of the pump alone
(see
specification).
If poor, check the pump for contamination and if
necessary return the pump as described in
. Leak-check the pump. If the leak rate
> 1 x 10
-7
mbar l s
-1
(1 x 10
-5
Pa l s
-1
) consult Edwards
or your supplier.
The EXT is very noisy or there
is excessive vibration or both.
Is the pump rotational speed
the same as the resonant
frequency of the attached
system?
If so, change the natural frequency of your system
or isolate the pump using flexible bellows.
Is the vibration being
transmitted from the rotary
pump?
If so, fit flexible bellows or a vibration isolator in
the backing line.
Is the noise irregular and
getting progressively worse?
If so, a bearing is defective. Consult Edwards or your
supplier.
Is the EXT making a constant
high-pitched noise?
If so, the rotor is out of balance. Consult Edwards or
your supplier.
Table 11 - Fault finding (continued)
Symptom
Check
Action
Summary of Contents for EXT250 Series
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