From Vacuum Technology: Calculations in Chemistry


The remaining vacuum pumps to be discussed in this chapter fall into a group which remove gas particles from systems by sorption effects such as adsorption, chemisorption/gettering and implantation. They tend to be used on systems where any contamination of the vacuum by pump fluids, lubricants, etc. must be avoided. However, those pumps that remove gas particles exclusively by temperature-dependent gas adsorption on molecular sieves or Al 2O 3 (adsorption pumps) will not be discussed.

In high/UHV pumps where the pumping action is based on sorption effects, the removal of gas is brought about essentially by chemical reaction (gettering) at the surface of materials such as titanium. With some getter pumps, reactive metal surfaces are freshly generated during pump operation either by evaporation (as in titanium sublimation pumps) or by sputtering (as in sputter-ion pumps). With non-evaporable getter (NEG) pumps, the passive layer which is formed during reaction with gases such as O 2, N 2, H 2O, is removed by degassing in vacuum.

3.4.1 Sputter-ion Pumps (SIP)

The pumping action of a SIP is based on sorption processes initiated by gas ions formed in a Penning discharge (see Chapter 5) maintained by a strong (flux density 0.1 to 0.2 T), homogeneous magnetic field. Ions impinge on parallel cathode plates made of a getter material such as Ti and sputter the getter which adheres to nearby surfaces within the pump and adsorbs reactive gases. Gas ions with sufficient energy...

Products & Services
Diaphragm Valves
Diaphragm valves close by means of a flexible diaphragm attached to a compressor.
Pinch Valves
Pinch valves include any valve with a flexible elastomer body that can be pinched closed, cutting off flow, using a mechanism or fluid pressure.
Ball Valves
Ball valves are quarter-turn, straight-through valves that have a round closure element with matching rounded seats that permit uniform sealing stress. The valve gets its name from the ball that rotates to open and close the valve. Ball valves are used in situations where tight shut-off is required. They are wide duty valves, able to transfer gases, liquids and liquids with suspended solids (slurries). Ball valves provide tight shut-off and characterizable control. They have high rangeability due to the design of the regulating element and few complications from side loads typical of butterfly or globe valves.
Butterfly Valves
Butterfly valves control flow through a circular disc or vane by turning the valve's pivot axis at right angles to the direction of flow in the pipe. They are normally used as throttling valves to control flow.
Globe Valves
Globe valves are linear motion valves with rounded bodies, from which their name is derived.  They are widely used in industry to regulate fluid flow in both on/off and throttling service. 

Topics of Interest

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