| A vacuum pump is a device that removes gas molecules from a sealed volume in order to leave behind a partial vacuum. The vacuum pump was invented in 1650 by Otto Von Guerickie.
Vacuum pumps are used in many industries and scientific processes including electric lamps, vacuum tubes, cathode ray tubes, semi conductors, electron microscopy, radio therapy, radio surgery, radio pharmacy, mass spectrometers, vacuum coatings, glass coatings, ophthalmic coatings, trash compactor, trash compactor, freeze drying and air conditioning.
Pumps can be broadly categorized according to three techniques:
Positive displacement pumps:
Positive displacement pumps use a mechanism to repeatedly expand a cavity, allow gases to flow in from the chamber, seal off the cavity and exhaust it to the atmosphere. Positive displacement pumps are the most effective for low vacuums. Positive displacement pump works simply as a manual water pump. It evacuates a chamber indefinitely without requiring the growth. A compartment of the vacuum can be repeatedly closed off, exhausted and expanded again.
Supporting the only basic principal, positive displacement pumps are used in most industrial applications as rotary vane pump, diaphragm pump, liquid ring vacuum pump, piston pump, scroll pump, screw pump, wankel pump, external vane pump, booster pump, multistage roots pump and toepler pump.
Momentum transfer pumps:
Momentum transfer pumps are also called as molecular pumps and use high speed jets of dense fluid or high speed rotating blades to knock gaseous molecules out of the chamber. Momentum transfer pumps are in conjunction with one or two positive displacement pumps and used to achieve high vacuums.
The two main types of momentum transfer pumps are the diffusion pump and the turbo molecular pump. Both the types of pumps blow out gas molecules that diffuse into the pump by imparting momentum to the gas molecules. Diffusion pumps blow out gas molecules with the help of jets of oil or mercury, while the turbo molecular pump use high speed fans to push the gas.
Entrapment pumps:
Entrapment pumps capture gases in a solid or absorbed state. Entrapment pumps can be used to reach ultrahigh vacuums, but they require periodic regeneration of the surfaces that trap air molecules or ions. Entrapment pumps may be cryo pumps, which use cold temperatures to condense gases to a solid or absorbed state. Chemical pumps, which react with gases to produce a solid residue or ionization pumps, which use strong electrical fields to ionize gases and propel the ions into a solid substrate.
Vacuum pumps also differ in details as manufacturing tolerances, sealing material, pressure, flow, admission and non admission of oil vapor, service intervals, reliability, tolerance to dust, tolerance to chemicals, tolerance to liquid and vibrations. |
