Ulvac CRYO-U Series Instruction Manual page 18

minutes of regeneration.
Gas exhausted from cryopump during regeneration has a pungent odor, similar to
②
that produced in arc welding operation.
A lot of ozone causes an intense explosion, and is very dangerous. In case of
pumping ozone by the cryopump, the following safety precautions must be taken.
1. Suppress the amount of ozone captured in the pump below an allowable value by
increasing the frequency of regeneration. A required regeneration cycle depends on
the flow rate of oxygen gas and other process conditions.
2. Reduce the flow rate of oxygen gas to the minimum as far as it does not influence the
process performance.
3. Reconfirm the safety required if the process condition is changed, as it might increase
ozone yield.
When using oxygen as a process gas, appropriate safety precaution and measures
must be taken with reference to "6. Regeneration after pumping flammable, explosive, or
combustion enhancing gas".
6. Regeneration after pumping flammable,
explosive, or combustion enhancing gas
When regenerating the cryopump after pumping flammable, explosive, or combustion
enhancing gas, those gases must be safely vaporized again and exhausted. Following
safety measures on the regeneration method are extremely important for employing the
cryopump safely. Please take proper safety precautions and measures from both hardware
and process software points of view. Also, recognize there is a risk that some hazardous
gas would be secondarily produced in the vacuum chamber as a result of plasma reaction
or the like.
1. Safety measures for regeneration
Following are the safety measures which you should prepare and implement
regarding regeneration process after pumping flammable gas, explosive gas, or
combustion enhancing gas. Please take necessary measures referring to figure.2.
Moreover, you may have to take additional safety measures depending on the kind of
the gas used, the process conditions, or the environment used. Be sure to take
required and sufficient safety precautions according to actual conditions.
S-6 ULVAC CRYOGENICS INCORPORATED