Ulvac CRYOPUMP CRYO-U Series Instruction Manual page 97

CRYO-U Cryopump Instruction Manual
®
1. Dew Condensation on a Cryopump
A cryopump accumulates frozen gases on the inside arrays using refrigeration.
condensation may occur on the cryopump case under the conditions as follows. Cares must be
taken to prevent short circuit in electrical parts around the cryopump.
When
(1)
(2)
In Operation
(3)
(4)
In
Regeneration
(5)
Appendix F
DEW CONDENSATION
Cause of Condensation
Dew condensation occurs as the
surface of the cryopump case
reaches dew point under current
ambient temperature and humidity.
Residual moisture inside is frozen
due to insufficient regeneration.
Vacuum level inside the cryopump
is insufficient during cooldown.
Frozen gases that have been
accumulated fall from the inner kit.
Residual moisture is frozen during
rough pumping
ULVAC CRYOGENICS INCORPORATED
Corrective Action
Use an air conditioner to keep optimal
temperature and humidity.
Refer to the Dew Point Table on the next
page.
Perform the regeneration work again,
confirm that the cryopump passes the
pressure buildup check, and start cooling
down.
If the vacuum level does not improve,
rough pump again with a dry pump that
has no oil backflow.
When the vacuum level is gradually
improving, adiabatic vacuum is kept when
the cooldown is completed and dew
disappears.
Use band heaters for regeneration.
Use heat insulating
condensation is severe.
Go through the regeneration process
again, confirm that the cryopump passes
the pressure buildup check, and start
refrigeration.
Dew
material when
F-1