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To achieve a higher vacuum, other techniques must then be used, typically in series (usually following an initial fast pump down with a positive displacement pump). Some examples might be use of an oil sealed rotary vane pump (the most common positive displacement pump) backing a diffusion pump, or a dry scroll pump backing a turbomolecular pump.
The most common sources of trouble (out-gassing) in vacuum systems are: Cadmium, often present in the form of cadmium plating, or in some soldering and brazing alloys; Zinc, problematic for high vacuum and higher temperatures, present in some construction alloys, e.g. brass and some brazing alloys.
Vacuum systems usually consist of gauges, vapor jet and pumps, vapor traps and valves along with other extensional piping. A vessel that is operating under vacuum system may be any of these types such as processing tank, steam simulator, particle accelerator, or any other type of space that has an enclosed chamber to maintain the system in less than atmospheric gas pressure.
Vacuum technology is based on differential air pressure. Rotary vane vacuum pumps generate an operation pressure of -0.4 to -0.6 bar at the vacuum station, which is also the only element of the vacuum sewerage system that must be supplied with electricity. Interface valves are installed inside the collection chambers. They work pneumatically.
The sorption pump is a vacuum pump that creates a vacuum by adsorbing molecules on a very porous material like molecular sieve which is cooled by a cryogen, typically liquid nitrogen. The ultimate pressure is about 10 −2 mbar. With special techniques this can be lowered till 10 −7 mbar.
A vacuum ejector, or simply ejector, or aspirator, is a type of vacuum pump, which produces vacuum by means of the Venturi effect.. In an ejector, a working fluid (liquid or gaseous) flows through a jet nozzle into a tube that first narrows and then expands in cross-sectional area.
The term "roughing pump" derives from the vacuum range it works in, "rough vacuum", above 1x10 −3 torr (0.1 Pa). Pumps that operate in the high vacuum ranges typically don't operate, or only operate inefficiently, at atmospheric pressures , whereas pumps that work efficiently at atmospheric pressure usually cannot produce a vacuum lower than ...
A molecular drag pump is a type of vacuum pump that utilizes the drag of air molecules against a rotating surface. [1] The most common sub-type is the Holweck pump, which contains a rotating cylinder with spiral grooves which direct the gas from the high vacuum side of the pump to the low vacuum side of the pump. [2]