Fault
The pump does not rotate after a serial start command is sent
Cause
Check if the pump returns a reply to the start command.
Remedy
If there is no reply, do the checks given in
or do the checks
given in
The pump does not rotate after a parallel start command is sent on page 76
.
Fault
The pump does not respond in multi- drop mode
Cause
The multi-drop is disabled.
Remedy
Make sure the pump has a multi-drop address. Make sure that the commands are sent
using the multi
‑
drop protocol.
Fault
The green Normal LED does not light or the pump does not rotate at full speed or the
pump fails while in operation
Cause
The inlet pressure is too high.
Remedy
Reduce the pumping load or check for a gross leak into the system.
Cause
The pump is too hot when in operation.
Remedy
• Increase the cooling to the pump. Change from air cooling to water cooling (refer
to
for maximum inlet pressure and cooling
requirements).
• Increase cooling water flow or decrease the water temperature or do both.
• Check that external heat sources (such as system bakeout heaters) are not
excessive.
Cause
The rotor does not rotate freely.
Remedy
The pump bearings may be damaged. Contact supplier or us.
Fault
Ultimate pressure cannot be reached
Cause
Pressure is limited by water vapour.
Remedy
Bake the system and pump.
Cause
The vacuum gauges are contaminated.
Remedy
Clean or replace the vacuum gauges.
Cause
Pumping speed is not sufficient (because of poor conductance between the pump
and the gauge or the chamber is too large).
Remedy
Increase the conductance or decrease the volume.
Cause
Inlet pressure is more than 0.5 mbar (50 Pa).
Remedy
If the interstage inlet pressure is too high, the inlet pressure at the turbomolecular inlet
is increased. Make sure that the interstage inlet pressure is less than 0.5 mbar (50 Pa).
Cause
The backing pressure is more than 10 mbar (1x10
3
Pa).
Remedy
The backing pressure can be too high. Check for backing pipeline leaks. If the
throughput is high, a larger backing pump can be necessary.
Cause
The high vacuum area of the system is contaminated.
Page 77
B85200880_D - Fault finding
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