Ulvac CRYO-U Series, Instruction Manual

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Figure 2 Dilution of Oxygen/Flammable Gas
①
Whenever the cryopump has stopped regardless of causes of control order or power
failure, etc., it is necessary to immediately carry out the regeneration, which is
based on warm-up assisted with inert gas, in order to exhaust a flammable,
explosive, or combustion enhancing gas safely from the cryopump. For the
details of the regeneration, refer to “6.3 Warm-up Method” in Section 6. As for the
inert gas, use nitrogen gas that its dew point temperature is -40 ℃ or below or argon.
(In this instruction manual, the terms “inert gas” or “dry nitrogen or argon” mean
“nitrogen gas that its dew point temperature is -40 ℃ or below or argon”.)
Both the purge of the cryopump and the dilution of the exhaust duct with the inert gas
are required to reduce the concentration of hazardous gas and keep it under a
certain level where the gas does not burn or explode even when it evaporates during
warm-up.
Please fix up the purge flow rate, the dilution flow rate, and regeneration time period
(which related with the pumping capacity of flammable gas) and take measures
required before starting the cryopump operation.
② When the above regeneration is delayed or it is not conducted, all the gases captured
in the cryopump will be evaporated by natural temperature rise. After that, cryopump
pressure may reach to the atmospheric pressure easily or exceed it easily
depending on the amount of captured gases.
At this moment, however, never do evacuation of the hazardous gases remained in
the cryopump by using a roughing pump. Because, there is a possibility that such a
hazardous gas may explode in the roughing pump.
In order to exhaust the dangerous gas from the cryopump safely after
IN
R
OUT
D i lu t ion
Ine r t gas
P ressu re re l ie f va lve
CRYO -U
C h am b e r
O u t d o o r
- Use metallic pipe and grounding.
- Determine the pipe diameter that can
prevent the pressure loss, considering the
length to the outside.
Exhaust line
Chamber
Outdoor
CRYO-U®
Inert gas
Inert gas
Pressure relief valve
ULVAC CRYOGENICS INCORPORATED S - 7