Ulvac CRYO-U12H, Instruction Manual

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CRYO-U ® Cryopump Instruction Manual
ULVAC CRYOGENICS INCORPORATED F-1
Appendix F
DEW CONDENSATION
1. Dew Condensation on a Cryopump
A cryopump accumulates frozen gases on the inside arrays using refrigeration. Dew
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 Cause of Condensation Corrective Action
In Operation
(1)
Dew condensation occurs as the
surface of the cryopump case
reaches dew point under current
ambient temperature and humidity.
Use an air conditioner to keep optimal
temperature and humidity.
Refer to the Dew Point Table on the next
page.
(2)
Residual moisture inside is frozen
due to insufficient regeneration.
Perform the regeneration work again,
confirm that the cryopump passes the
pressure buildup check, and start cooling
down.
(3)
Vacuum level inside the cryopump
is insufficient during cooldown.
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.
In
Regeneration
(4)
Frozen gases that have been
accumulated fall from the inner kit.
Use band heaters for regeneration.
Use heat insulating material when
condensation is severe.
(5)
Residual moisture is frozen during
rough pumping
Go through the regeneration process
again, confirm that the cryopump passes
the pressure buildup check, and start
refrigeration.