Ulvac CRYO-U Series, Инструкция по эксплуатации

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Troubleshooting
A-4 ULVAC CRYOGENICS INCORPORATED
Problem Possible cause Corrective action
(Continued) 4) Failure of the refrigerator unit or
the compressor unit.
Contact our Service Engineering
Division or the nearest CS center.
Ⅴ．
Pumping performance
of the cryopump is
lowered.
Examples
・
Temperature is higher
than the normal value.
・
Pumping speed is
falling.
･
Vacuum level has
worsened.
･
Helium gas filling
pressure is lower than
the specified value.
1) The ultimate pressure of the
vacuum chamber after roughing is
still high.
Rough pump to the maximum
allowable crossover pressure or less
(Recommended value: 40Pa). Refer
to Sec. 5.6 for details.
2) A large amount of gas has been
captured.
Regenerate the cryopump as
described in Sec.6.
3) High partial pressure of helium
remained in the cryopump.
Purge helium with dry nitrogen gas to
reduce the partial pressure of helium.
4) Leakage
①
Air-to-vacuum leakage at
attaching parts or ports on the
cryopump.
②
Helium leakage caused by the
slack of helium gas joint.
Detect the leakage by the evacuation
method using a helium leak detector
or mass analyzer, and stop the
leakage.
Detect the leak point by Sniffer
method using a helium leak detect
or or by the bubbling method with
soap, and stop the leakage.
If no leak is found, contact our
Service Engineering Division or the
nearest CS center.
5) Internal equipments of the
cryopump becomes loose in
the following parts:
①
Thermometer mounting bolts.
②
Mounting bolts of 80K shield,
80K baffle, and 15K cryopanel.
If necessary, disassemble the
cryopump and remount the
temperature sensing part firmly to the
second stage of the refrigerator unit.
Replacement of the indium sheet is
required.
If necessary, disassemble the
cryopump and retighten all screws.
Replacement of the indium sheet
is required.