Troubleshooting Procedures - HELIX CTI-CRYOGENICS CRYO-TORR 100 Installation, Operation And Servicing Instructions

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Appendix A:
Troubleshooting
Procedures
A.1 Troubleshooting the Cryopump
A.2
Technical Inquiries . . . . . . . .
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HELIX TECHNOLOGY CORPORATION
A·1
A·1
A.1 Troubleshooting the
Cryopump
A.2 Technicallnquiries
The primary indication of irouble in a vacuum pumping
system is a rise in the base pressure of your vacuum
chamber. A rise in the base pressure may be caused by a
leak in the vacuum system or by a fault in the cryopump
i.e., saturation of the 15K cryo-adsorbing charcoal array.
(Regeneration may be necessary). If the cryopump
temperature is below 20K it must pump at rated
capacity; a high base pressure is usually caused by an
air-to-vacuum leak in the system.
If you suspect a leak in your vacuum system, isolate the
cryopump by closing the Hi-Vac valve and leak check
your vacuum chamber. If no leaks are found, a leak may
be present below the Hi-Vac valve (cryopump). Leak
checking below the Hi-Vac valve should be performed
with the cryopurnp shut off and at room temperature.
Leak checking while the cryopump is operating may
mask leaks that are present (due to the ability of the
cryopurnp to pump helium). If no leak is found, refer to
the cryopump troubleshooting procedures summarized in
TableA.l.
The problems presented in the Troubleshooting Table
are followed by possible causes and corrective actions.
The causes and corresponding actions are listed in their
order of probability of occurrence.
1)
is most likely,
2)
is next most likely, etc.
Maintaining a log of certain parameters during normal
operation can be a valuable tool in iroubleshooting the
cryopurnp. The parameters included in the log should
include as a minimum the following: the cooldown time
to 20K; the roughing time to 50j.l; the time to base
pressure at crossover; the time between regeneration;
and the compressor pressure reading.
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