The following troubleshooting tips
cover very basic cryopump maintenance and troubleshooting. If you require
detailed technical assistance please contact the pump manufacturer.
You are of course welcome to contact SFC
Most cryopumps provide years of trouble-free
operation with little maintenance and down time. These pumps are not
maintenance-free however and knowing when and what to service can
save time and money on expensive overhauls or replacements. Always
follow the cryopump manufacturers instructions located in the system
The following tips cover a few of the more common
problems encountered when operating cryopumps.
Symptom: Increase in ultimate pressure or
normal operating temperature.
Unlike a turbo or diffusion vacuum pump the cryopump
retains all of the gases it has pumped and will eventually need to
be emptied. (Regeneration)
Generally, If the compressor is operating, the cold head is
quietly turning and the temperature is in the normal range, the only
possible cause of pressure increase is a full pump or increased gas
load such as a leak. Perform a helium leak test on the vacuum
system and regenerate the cryopump per the
Symptom: Cryopump failing rate-of-rise-test
after regeneration. Regeneration completed but pressure and
temperature problems still exist.
If the cryopump has been exposed to atmosphere while
cold, an additional or extended regeneration may be necessary.
Roughing the cryopump for extended periods or opening the rough
valve while the pump is cold can allow contamination from mechanical
pump oil back-streaming. The interval between array replacement
varies greatly depending on the type and conditions of normal use.
If the extra regeneration does not correct the problem the
15K Charcoal array may need
to be replaced.
Symptom: The cold head is making strange
If the cold head runs smoothly until it has begun to
cool and suddenly starts to make ratcheting sounds or otherwise
stops turning smoothly, the helium circuit has become contaminated.
Severe contamination may cause the pump mechanism to seize.
Perform the decontamination procedure per manufacturers
instructions. This procedure is not difficult but does require a
maintenance manifold and care should be taken to follow the
If the cryopump compressor starts and continues to
run for half an hour it's probably okay. It may require service but
at least it's not dead. The adsorber should be changed at the proper
intervals as specified by the manufacturer. If not changed the
adsorber can allow compressor oil into the helium circuit which can
lead to costly repairs. Adsorber replacement for most compressors is
a simple task but again, the installation instructions should be
Correct helium pressure within the compressor is very
important. Low pressure can result in high pump temperature and may
indicate a leak in the helium circuit. Higher than normal pressure
can cause the compressor overload to trip. Check both static and
dynamic pressures against the specifications for your specific unit.
If you find you are having to add helium more than once or twice a
year, there is probably a leak somewhere in the helium circuit. Use
a helium leak detector to isolate the leak.
Improper line voltage, frequency and phase can cause
numerous cryopump system malfunctions. Insure that the compressor
and pump are connected exactly as indicated in the installation
manual and verify the proper voltage and phase of input power.
Symptoms of improper power connections and/or connections can
include complete failure to operate, sluggish or stopped cold head
operation, tripping of compressor breakers, and others. Check the
installation manual for power requirements and connections.
Specialty Fluids Company is not affiliated with Brooks Automation
or Austin Scientific in any way.
OnBoard, CTI-Cryogenics, CT-8 and CT-10 are registered trademarks of Helix
Technology Corp., Brooks Automation
is a registered trademark of Austin Scientific Co., Oxford