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Technical Information
Explosion
Operation of the diffusion pump without continuous evacuation below 0.5 Torr
(0.67 mbar), or without coolant and introducing a strong oxidizer (such as air)
or explosive vapors or powders or materials which may react with pumping
fluids in a hot pump (above 300 °F or 150 °C) can cause an explosion. Such an
explosion can violently expel valves and other hardware, slam open doors that
are not designed for appropriate pressure relief, or burst other components of
the vacuum system. Serious injury or death may result from expelled parts,
doors, shrapnel, and shock waves.
Three elements are required for explosion: fuel, oxidizer, and an ignition. A
combination of temperature and pressure can be a source of ignition. Most
diffusion pump fluids are fuels. Hydrocarbon fluids are more prone to oxidize
and explode than synthetic silicone-based fluid. The oxidizer can be air, which
can be introduced by a leak, deliberately brought in via a process, or
inadvertently admitted by operator error.
Oxygen and other strong oxidizers are even more dangerous than air. Certain
conditions of temperature and pressure can cause a combustible mixture to
explode. The larger the diffusion pump, the greater the risk of explosion and the
greater the risk of damage and injury. Never operate large diffusion pumps
utilizing hydrocarbon oils without a complete safety analysis for the entire
system and for the application.
Explosion and Fire from Acetone and Alcohol: Diffusion pumps are typically
cleaned with acetone and alcohol. When combined with air, oxygen, and other
oxides, alcohol and most other solvents are very flammable and explosive.
Never permit any trace of these cleaners to remain in or on the pump. Always
remove all traces of alcohol and acetone and other cleaners with clean, dry, oil-
free compressed air
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High Throughput Diffusion Pumps User Manual
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