Ulvac CRYO-U Series, Instruction Manual

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Troubleshooting
A-6 ULVAC CRYOGENICS INCORPORATED
Problem Possible cause Corrective action
Ⅵ．
Regeneration is
required at short
intervals.
1) Incomplete regeneration
Regeneration temperature is so
low that the water in the absorbent
cannot be dried out.
①
Perform regeneration as
described in Sec.6. Warm the first
stage and the second stage up to
room temperature.
②
Repeat introduction of dry
nitrogen gas and rough pumping.
This is the most effective way.
③
After rough pumping, confirm that
the pressure buildup speed from
40Pa is 1.3Pa/min or less.
2) Leakage in vacuum system. Detect and stop the leakage.
Ⅶ．
Refrigerator drive
motor is making
irregular or
intermittent motion.
1) Helium gas is heavily
contaminated.
Perform cryopump decontamina-
tion procedures as described in
Sec.8.5. Use helium gas with pur
ity of 99.999% or more.
2) Input voltage to the motor is low.
Check the input voltage to the
compressor and the refrigerator.
Optimum voltage of the refrigera-
tor unit is 144V for two-phase
motor and 200V for three-phase
motor.
Because it should be a check
under the hot line condition, an
appropriate maintenance person
in charge needs to check.