Ulvac CRYO-U Series, Instruction Manual, Page: 73 / 106

CRYO-U
®
Cryopump Instruction Manual
ULVAC CRYOGENICS INCORPORATED 8-5
WARNING
The following are the recommended maintenance procedures of the pressure relief valve.
This maintenance is required once or twice a month. Confirm the safety of the gases exhausted
into the cryopump before beginning the maintenance, since the inner kit in the cryopump is
exposed to atmosphere when cleaning the pressure relief valve.
1. Remove the cap from the pressure relief valve.
2. Clean the pressure relief valve and the cap using the cloth moistened with alcohol.
Reinstall the valve and the cap after they dry.
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Maintenance of heater for regeneration
(Applicable only to a cryopump system with heater)
Periodical maintenance is required as shown in Table 8-1.
Heaters for regeneration, both sheathed type and cartridge type, have a possibility of
deterioration of nonconductivity with age. Be sure to install a ground-fault circuit interrupter,
and conduct periodic inspections of the nonconductivity to prevent a short circuit.
8.4 Charging Helium Gas
Please supply the equipments for charging helium gas (regulators, charging hoses) that can be
used at 2.0MPaG or above.
If the helium pressure gauge of the compressor unit shows 0 MPaG, contamination caused by
air or moisture may occur in the system. If it occurs, contact our Service Engineering Division
or customer support center.
When helium gas pressure is lowered, it is necessary to add helium. Investigate the cause of
the pressure reduction before adding helium gas. If there is a leakage, take an adequate
measure before charging. Improperly connected self-sealing coupling is one of the causes of
leakage.
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Recommended regulator is the one designed for helium gas (left-hand thread) and has the
pressure gauge of 4-6MPaG on low pressure side.
CAUTION