Ulvac CRYOPUMP CRYO-U Series Instruction Manual page 81

CRYO-U Cryopump Instruction Manual
®
Problem
Ⅲ．(Continued)
A compressor unit
starts, but a cryopump
doesn't start. Or the
cryopump is stopped,
but the compressor
unit is running
continuously.
Ⅳ．
The cryopump fails to
cool down to 20K or
lower at the time of
startup.
Possible cause
3) The drive motor of a refrigerator
unit has mechanical damage.
① Motor shaft failure or bearing
defects.
② Drive motor circuit failure.
1) Helium Supply/Return line
incorrectly connected.
Self-sealing coupling is not
fully tightened.
2) Pressure in the cryopump is too
high.
3) Heat load to the cryopump is
too high.
ULVAC CRYOGENICS INCORPORATED
Corrective action
Check whether there is sound which
shows a motion of a motor by turning on
and off the switch of the refrigerator.
When no sound or irregular beat comes
from the motor, contact our Service
Engineering Division or the nearest CS
center.
Measure resistance and insulation
resistance between the drive motor
connector pins (Impressed voltage: DC
500V) and inform us the measured
values with S/N of the refrigerator unit.
Properly connect the flexible hoses
referring to Sec. 4.7.
Check that all self-sealing couplings
are fully connected referring to Figure
4-5.
Make sure that there is no leakage.
The cryopump may fail to cool down
due to thermal load of the gas caused
by a leakage.
If the temperature of the cryopump
rises when opening the main valve,
heat input amount from the user's
device is over the acceptable value. In
this case, take measures to reduce the
heat load.
If the cryopump still fails to cool down
to 20K or lower even when the main
valve is closed, the refrigerator unit
may be out of order. Contact our
Service Engineering Division or the
nearest CS center.
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