© Edwards Limited 2013. All rights reserved. Page 55
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Maintenance
B722-40-880 Issue F
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 interstage inlet pressure
>0.5 mbar (50 Pa)
If the interstage inlet pressure is too
high, inlet pressure at the
turbomolecular inlet is increased;
ensure that the interstage inlet
pressure is <0.5 mbar (50 Pa).
Is the backing pressure
>10 mbar (1x10
3
Pa)
If so, the backing pressure may be
too high. Check for backing pipeline
leaks. If the throughput is high, a
larger backing pump may be
required.
Is the high vacuum area of the
system contaminated?
If so, clean the high vacuum system.
Check the rest of the system for
leaks and contamination.
If found, repair the leaks and clean
the contamination.
Remove the pump from the system
and test the ultimate pressure of the
pump alone (refer to Section 2)
If inlet pressure is poor, check the
pump for contamination and refer to
Section 5. Leak test the pump. If the
leak rate >1x10
-7
mbar l s
-1
(1x10
-5
Pa l s
-1
) contact the supplier
or Edwards.
The pump 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 the system or isolate the pump
using flexible bellows.
Is the vibration being transmitted
from the rotary backing 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. Contact
the supplier or Edwards.
Is the pump making a constant high
pitched noise?
If so, the rotor is out of balance.
Contact the supplier or Edwards.
Any other problems - Contact the supplier or Edwards.
Table 23 - Fault finding (continued)
Symptom Check Action
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