Ulvac CRYOPUMP CRYO-U Series Instruction Manual page 17

 Ignition by static electricity
 Ignition by liquid ozone
If a roughing pipe or exhaust line is made of plastic such as vinyl chloride, it may produce
static electricity.
On the other hand, ozone may generate under the process utilizing plasma with oxygen or
CO gas. Captured and condensed ozone in the pump liquefies in the warm-up process of
X
regeneration. Note here is the following. The liquid ozone is so unstable that it might
explode by impact or ignition resulting from the reaction with organic matter.
In case of a pumping flammable or explosive gas(es), appropriate safety precaution must
be taken with reference to "6. Regeneration after pumping flammable, explosive, or
combustion enhancing gas".
5. When pumping oxygen
Mixing oxygen and flammable gas invites danger.
Oxygen enhances combustion. Use the cryopump after confirming the safety
precautions or measures when pumping the mixture of oxygen and flammable
gas into the cryopump. In particular, mixed gas of oxygen and hydrogen has a
broad range of combustion/detonation and is extremely dangerous.
The mixes gas with hydrogen of 4% or more and oxygen of 5% or more at atmospheric
pressure could cause explosion momentarily (refer to "4.When pumping flammable or
explosive gases").
When oxygen is used as a process gas, appropriate safety precautions must be taken with
reference to "6. Regeneration after pumping flammable, explosive, or combustion
enhancing gas".
Oxygen may generate ozone.
Ozone may be unexpectedly generated in plasma production process (e.g.,
sputtering, etching, glow discharge, EB deposition). Ozone pumped and
condensed in the cryopump liquefies in the warm-up process of regeneration. The liquid
ozone at high concentrations might explode by impact or ignition by the reaction with
organic matter. In case that large amount of ozone is generated in the process and
accumulated in the cryopump, following may be observed at the time of regeneration:
(1) Cracking/popping sounds (as in electrical arching) is heard in the first few minutes
of regeneration.
ULVAC CRYOGENICS INCORPORATED S-5