HELIX CTI-CRYOGENICS CRYO-TORR 100 Installation, Operation And Servicing Instructions page 27

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5.5 Normal Operation
The Cryo-Torr high-vacuum pump system is designed to
operate without operator assistance.
As an aid to evaluating performance it may be
advantageous
to
record basic parameters at a regularly
scheduled period. An ideal time is
to
coordinate this
practice with other maintenance items or whenever
regeneration is required. On new systems record this
data at least on a monthly basis.
5.6 Cryopump Oxygen Procedures
AWARNING
Combustion supported by oxygen in the pump
could cause severe injury. When oxygen is used as a
process gas, special precautions should be taken.
When using oxygen as a process gas, it is strongly
recommended that as a minimum, the following
precautions be taken.
1.
Follow all cryopump operating instructions
including:
• Insure that there are no sources of iguition (e.g.,
hot filament vacuum gauges) on the cryopump
side of the Hi-Vac valve operating during the
warming or venting of the pump.
• Perform inert gas purge regenerations at flow
rates recommended for cryopumps.
2. Regenerate as frequently as practical to minimize
the amount of oxidizer present in the cryopump.
3. Provide proper and appropriate venting for the
cryopump relief valve to vent exhaust gases.
4. Any system exposed to richer-than-air oxygen levels
should be prepared for oxygen service per the
manufacturer's recommendations, including use of
oxygen service lubricating oils in roughing pumps.
5-3
eTl-CRYOGENICS
HE.L1X TE.CHNOLOGY CORPORATION
AWARNING
Explosion occurring from ozone in the pump could
cause severe injury. Ozone can be present as a by-
product of oxygen processes. If ozone is present,
special precautions described in the text below must
betaken.
Ozone may be unknowingly produced in an ionizing
process (e.g., sputtering, etching, glow discharge).
Explosive conditions may exist if ozone is present,
especially during warming of the cryopump. Signs of
ozone's presence are:
1.
Crackling/popping sounds (as in electrical arcing)
occurring within the first few minutes of
regeneration.
2. Gas venting from the cryopump during regeneration
may have a pungent smell, similar to that present in
an arc welding operation or after an electrical storm.
Note: A change in process may increase the
amount of ozone present.
If ozone
is
present, the following precautions must be
taken, in addition to those already mentioned.
1.
The required regeneration frequency should be
increased depending upon flow and process
conditions. Daily regeneration may be required.
(Call CTI-CRYOGENICS for assistance.)
2. Reduce the oxygen mixture to the absolute lowest
level the process will allow.
3. Be sure that the system is properly vented to a
scrubber or to a safe area preferably outdoors.