© Edwards Limited 2011. All rights reserved. Page 69
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Maintenance
A705-40-880 Issue B
The pump operates at too high a
temperature or the pump
temperature is unstable. The coolant
filler-cap continuously opens to
release pressure in the cooling-
jacket.
Does the thermal snap-switch (if
fitted) not operate at the required
temperature?
Check the operation of the thermal
snap-switch as described above. Before
you restart the pump, check the
coolant level (refer to Section 5.10).
Does the ATEX control circuit not
operate at the required
temperature?
Check that the ATEX control circuit is
correctly configured: refer to the ATEX
System instruction manual.
Has the TCV been set correctly? Adjust the TCV to a lower temperature
setting (refer to Section 3.12.4).
Has the TCV failed? If the cooling-water supply is on and is
at the correct pressure, but there is no
flow indicated in the cooling-water
flow indicator, the TCV may have
failed: contact your supplier or
Edwards for advice.
The pump continues to operate at a
high temperature which may result
in seizure.
Is the pressure relief valve stuck in
the open position?
Inspect the pressure relief valve and
clean it or replace it if necessary (refer
to Section 5.7 and 5.14).
The pump only achieves an ultimate
pump-inlet pressure of 30 to 50 mbar
(3 x 10
3
to 5 x 10
3
Pa).
Is the pressure relief valve stuck in
the open position?
See above.
The pump-motor trips out due to
excessive electrical current
consumption when the EDP250 pump
is operating with pump- inlet
pressure in the range 300 to 1000
mbar (3.0 x 10
4
to 1 x 10
5
Pa), or
when the EDP400 pump is operating
with pump- inlet pressure in the
range 200 to 1000 mbar
(2.0 x 10
4
to 1 x 10
5
Pa).
Is the pressure relief valve stuck in
the closed position?
See above.
The gearbox and oil are
contaminated with the process
substances pumped.
Has the shaft-seals purge nitrogen
supply failed?
Check that there is a flow of nitrogen
purge to the shaft-seals (look at the
nitrogen flow indicator); if necessary
adjust the pressure regulator (refer to
Section 3.12.3). Change the gearbox
oil before you restart the pump (refer
to Section 5.8).
If you cannot adjust the pressure
regulator to the required pressure,
there is no flow; check your nitrogen
supply pressure and rectify as
necessary. Change the gearbox oil
before you restart the pump (refer to
Section 5.8).
Have the seals in the pump failed? The seals must be replaced. Contact
your supplier or Edwards for advice.
The gearbox is noisy. Is the oil level low? Check the oil level and fill as necessary
(refer to Section 5.3).
Table 17 - Fault finding (continued)
Symptom Check Action
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