Sumitomo Marathon CP-8 - TEMPERATURE CYCLING AND REFRIGERATION LOSS

Troubleshooting
59
Problem
Possible Cause
Corrective Action
Temperature is cycling. Contaminated gas is causing
a cold head freezing-thawing
cycle.
Perform Gas Cleanup and
Charging procedure on the cold
head (procedure in this manual)
and on the compressor and gas
lines. See their manuals. If the
problem remains, consult a
SCAI Service Center.
Sudden loss of refrigeration
capacity.
Loss of insulating vacuum. Check the vacuum system for
operation and leaks.
Compressor malfunction. Troubleshoot the compressor.
See the compressor manual.
Slow loss of refrigeration
capacity.
Small insulating vacuum leak. Leak check and repair the
vacuum system.
Cold head is leaking. Use the Leak Checking and
Leak Repair procedures in this
manual.
Worn seals. Use the appropriate cold head
Disassembly and Repair
procedures in the cold head
manual. Leaking seals will be
confirmed by a streaming
pattern of black particles on the
displacer near the seal rings.
During rough pumping,
pressure in the vacuum
enclosure will not fall low
enough to maintain an
adequate vacuum.
Vacuum chamber leaks. Leak check the system. Repair
the leaks. Refer to the Leak
Checking and Leak Repair
sections in this manual.
Outgassing is occurring. Vacuum bake the vacuum
chamber. Refer to the Vacuum
Baking sections in this manual.
Gas permeates the gaskets
and joints of the vacuum
chamber.
Review the gasket or seal
material and joint design. Check
that all bolts are tightened.
Cooldown time is excessively
long.
Oil contaminates the
cryopanels.
Clean the cryopump chamber.
Replace the cryopanels. Refer
to the Cryopanels section.