Edwards B777-01-000, Instruction Manual

Page: 30 / 38

B777-00-880 Issue E
Page 24 © Edwards Limited 2008. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
Maintenance
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 > values
given in
Table 7 ?
Check for backing line leaks. If the
backing pressure is too 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
Section 3 for
specification).
If poor, check the pump for
contamination and if necessary clean
as described in
Section 5.3 . Leak-
check the pump. If the leak rate
> 10
-7
mbar l s
-1
(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. Switch
off the pump and consult Edwards or
your supplier.
Is the EXT making a constant high-
pitched noise? If so, the rotor might be out of
balance. Consult Edwards or your
supplier.
None of the above. - Consult Edwards or your supplier.
Table 8 - Fault finding (continued)
Symptom Check Action