Telemark Cryogenics 1200 Instruction Manual page 52

Symptom Possible Cause
System has poor Too much heat is being applied to the
cooling with large cryo-coil
temperature
differential between
CI and CO
Possible refrigeration leak
(
Cryo-coil or refrigeration lines have
become damaged
)
System has poor Process problem
cooling with small
temperature
differential between
CI and CO
System is slow to
cool
Damaged refrigeration lines especially
the cryo-coil and return refrigerant line
System is placed in cool too soon after
Cryo-coil has too big a thermal mass
Telemark Cryogenics Microprocessor Based Cryochillers
" *
termination of defrost
Page 52 of 63
Corrective Action
Remove Internal heat source
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.
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
The UNIT is designed to have a
maximum stabilised temperature
differential between CI and CO
o
values of 20 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
-3
10 mbar – Consult tables in
section 4
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
Check line for blockages and
twists.
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
Redesign cryo-coil using thinner
gauge material
Revision 1.0.7 October 2018