Ulvac CRYO-U Series Instruction Manual page 88

Troubleshooting
Problem
Ⅵ．
Regeneration is
required at short
intervals.
Ⅶ．
Refrigerator drive
motor is making
irregular or
intermittent motion.
A-6
Possible cause
1) Incomplete regeneration
Regeneration temperature is so
low that the water in the absorbent
cannot be dried out.
2) Leakage in vacuum system.
1) Helium gas is heavily
contaminated.
2) Input voltage to the motor is low.
ULVAC CRYOGENICS INCORPORATED
Corrective action
①Perform regeneration as
described in Sec.6. Warm the first
stage and the second stage up to
room temperature.
② Repeat
introduction
nitrogen gas and rough pumping.
This is the most effective way.
③After rough pumping, confirm that
the pressure buildup speed from
40Pa is 1.3Pa/min or less.
Detect and stop the leakage.
Perform cryopump decontamina-
tion procedures as described in
Sec.8.5. Use helium gas with pur
ity of 99.999% or more.
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.
of dry