Vacuum pump

A vacuum pump is a pump that removes gas to leave behind a partial vacuum (of varying quality, depending on the pump). Various mechanisms can be used; sometimes more than one will be used (in series or in parallel) in a single application.

Related Topics:
Pump - Vacuum - Series - Parallel

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

A partial vacuum can be created using a positive displacement pump that transports a gas load from an inlet port to an outlet (exhaust) port. Because of their mechanical limitations, such pumps can only achieve a fairly crude partial vacuum. To achieve a more-perfect vacuum, other techniques must then be used (usually following an initial fast "pump down" using a positive displacement pump). In a turbomolecular pump, the momentum transfer principle is used, accelerating the gas molecules from the vacuum side to the exhaust side (which is usually maintained at a reduced pressure by a positive displacement pump). Another alternative is cryogenic entrapment where individual gas molecules are liquified and contained in a cold trap.

Related Topics:
Turbomolecular pump - Momentum - Cryogenic - Cold trap

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Achieving truly high vacuums is difficult because all of the materials exposed to the vacuum must be carefully evaluated for their outgassing properties. For example, oils, greases, rubber, or plastic used to form gaskets and seals must not boil off when exposed to the vacuum or the gases they produced would prevent the creation of the desired degree of vacuum. Often, all of the surfaces exposed to the vacuum must be baked at high temperature to drive off adsorbed gases.

Related Topics:
Outgassing - Oil - Grease - Rubber - Plastic - Gasket - Seal - Boil - Adsorbed

~ ~ ~ ~ ~ ~ ~ ~ ~ ~