Ulvac CRYO-U Series Instruction Manual page 20

stopping the cryopump, be sure to purge them out to the exhaust duct with
inert gas before pumping by a roughing pump.
③ Eliminate ignition factor. Insure that there are no sources of ignition (refer to "4. When
pumping flammable or explosive gases") on the cryopump side during regeneration.
④ Be sure to use metallic pipes for the roughing system and exhaust lines in order to
prevent generation of static electricity. Ground the pipes with the grounding
resistance of 100 Ωor less.
⑤ In case that the gas to be exhausted is hazardous and lighter than the dilution gas
(such as hydrogen gas), design and install the exhaust pipes so that its lighter gas
should not be accumulated in the pipes.
⑥ Perform inert gas purge into the exhaust line in order to reduce the flammable gas
concentration below its combustion range before exhausting them away to
atmosphere.
⑦ Perform inert gas purge as the regeneration starts.
⑧ Assuming the pressure relief valve would work, connect the pressure relief valve to
the exhaust line in order to dilute the gases which might spout out from the valve.
⑨ Be sure not to rough pump the cryopump without inspecting the state of the pump
just after power failure. As mentioned in the above ②, reduce the concentration of
hazardous gases in the pump and exhaust line by adding inert gas before rough
pumping. It helps to exhaust the vaporized gas safely out of the pump in case power
failure occurred.
⑩ When adopting a oil-sealed rotary pump as a roughing pump, change lubricating oils
with Fomblin grease which is insensitive to oxygen. Instead, a drypump will be fully
recommended.
2. Safety measures in emergency
If the troubles such as blackout, water outage, or pneumatic abeyance cause
suspension of a cryopump, take either among the following two actions.
1) When the cause of failure is eliminated before the temperature of the 2
reaches 20K, restart the cryopump.
2) When the temperature of the 2
the cause is eliminated. It is necessary to prepare some adequate devices to
introduce an inert gas automatically into both the cryopump and exhaust duct. The
devices include a thermometer, a valve for purge inert gas to the cryopump, a
valve for exhausting gases from the cryopump, an atmospheric pressure sensor in
the cryopump and a valve for introducing dilution gas into the exhaust line.
S-8
nd
stage exceeds 20K, perform regeneration even if
ULVAC CRYOGENICS INCORPORATED
nd
stage