Telemark Cryogenics Microprocessor Based Cryochillers
Page
52
of
63
Revision 1.0.7 October 2018
System has poor
cooling with large
temperature
differential between
CI and CO
Too much heat is being applied to the
cryo-coil
Remove Internal heat source
Possible refrigeration leak
Check values of
#(
'(
CT
-
While in cool, and standby and
compare with previous logged
values
("*
Consult Telemark for free
application advice. Aim for a cryo-
coil, which has low mass, high
surface area, low volume and a
small resistance to flow.
Cryo-coil or refrigeration lines have
become damaged
It is common for the refrigeration
lines to be twisted or damaged.
The entire refrigeration circuit
should be free from restrictions
)
Check defrost and suction line
hand valves have been opened
System has poor
cooling with small
temperature
differential between
CI and CO
Process problem The UNIT is designed to have a
maximum stabilised temperature
differential between CI and CO
values of 20
o
c. It is possible for
absolute temperatures and in
chamber conditions to vary for the
following reasons
Ambient humidity -
Moisture levels in substrate or poor
chamber cleaning increasing levels
of out-gassing
Poor process control especially if
substrate heaters are part of your
process.
If the cross over pressure is too
high when the UNIT is switched to
cool there is a significantly
increased heat load – aim for 5 x
10
-3
mbar – Consult tables in
section 4
System is slow to
cool
It typically takes 15 – 30 seconds
for an appreciable drop in the
temperature at CI. This may be
longer if remote sensors are being
used
Damaged refrigeration lines especially
the cryo-coil and return refrigerant line
Check line for blockages and
twists.
System is placed in cool too soon after
termination of defrost
The UNIT requires some time to
liquefy refrigerant to feed the cryo-
coil fully when in cool. Try
optimising your process by
lengthening the standby period
following a defrost. Typically 1
minute of extra standby will speed
cooling to the base temperature by
about 2 mins
Cryo-coil has too big a thermal mass Redesign cryo-coil using thinner
gauge material
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