Troubleshooting
26
GA12119_002_A3 - 01/2012 - © Oerlikon Leybold Vacuum
Malfunction at
the cold head
The refrigerating capaci-
ty of the cold head is
too low.
Cold head becomes
irregular or noisy.
Possible cause
Helium loss (pressure of helium
should be approx. 22 bar when
compressor unit is operating).
Contamination in the cold head.
Oil adsorber is saturated.
Cold-head motor turning in wrong
direction.
Insulating vacuum not in order.
Too much time since displacer
piston maintenance last perfor-
med.
Control valve worn or control disk
dirty.
Helium contaminated because
adsorber performance inadequa-
te.
Control valve worn or control disk
dirty.
External magnetic field exists
(> 30 mT=300 Gauß).
Fault correction
Refill with ultra-pure helium (99.999 %
purity or higher) at compressor unit.
‘
Use special adapter to relieve the pres-
sure at the cold-head high-pressure inta-
ke. Check the control disk and the valve.
Purge and refill with ultra-pure helium
while the cold-head motor is running.
Install a new oil adsorber.
Proceed as for “contamination”; check
direction of rotation.
Increase insulating vacuum to
< 10
-3
mbar.
Install a new displacer piston.
Install a new control valve or control disk.
Install a new oil adsorber and purge the
system as for “contamination”. Clean the
control disk and control valve.
Install a new control valve or control disk.
Reduce the magnetic field or shield the
cold head motor and then install a new
cold-head motor.
Repair note
Operating
Instructions for
the compressor
unit.
Trained personnel
only.
Operating
Instructions for
the compressor
unit.
Trained personnel
only.
--
Trained personnel
only.
Trained personnel
only.
Trained personnel
only.
Trained personnel
only.
Trained personnel
only.
6
Troubleshooting