Ulvac CRYOPUMP CRYO-U Series Instruction Manual page 16

3. Perform regeneration immediately
after shutting down cryopump
After shutting down the cryopump operation, proceed with warm-up and rough pumping as
part of regeneration process in order to maintain the cryopump in clean vacuum.
In many vacuum pumping processes, large amount of moisture is often captured and
condensed inside the cryopump. If the cryopump is left without appropriate care after
shutdown, captured moisture will react with internal parts, resulting in corrosion.
Moreover, if corrosion of internal parts continues, pumping performance may deteriorate
resulting in extended cooling time or rise of ultimate temperature.
Make sure to perform regeneration immediately after shutting down the cryopump in order
to remove water vapor. Following three steps in the regeneration sequence mentioned in
Section 6.4 are required; 1) Warm-up, 2) Discharge (desorption) of captured gas, and 3)
Pressure buildup check.
Such corrosion of inner kits might occur depending on the kind or amount of the process
gases. Also, note that when the inner kits need to be replaced due to corrosion, such
service should be payed even within the guaranteed term.
4. Cautions when pumping flammable
or explosive gases
Hydrogen has both flammability and explosiveness. When a flammable or explosive
gas is pumped with the cryopump, it must be removed safely from the pump in the
warm-up process of regeneration. Be sure to take the following safety precautions.
(1). Control and manage the process condition, the time period and method of
regeneration in order to keep the concentration of the hazardous gases
discharged to the exhaust duct below an allowable value.
(2). Eliminate ignition factors completely from the pump and duct.
(3). Make sure that the safety precautions mentioned above can work well even in
any abnormal events.
Possible causes of ignition in the vacuum equipment are as follows:
 Ignition by a vacuum gauge filament being turned on
 Ignition by a heater with heating element(s) exposed into the process
circumstance or the like
S-4 ULVAC CRYOGENICS INCORPORATED