4 - Pumping

Abstract

There are many pump types available and many different combinations of pumps that can be used to pump a system for any particular process. One of the types of pumps is the rotary pump that can be made with two different chambers so that the exhaust of one chamber is further increased in pressure by going through a second stage of compression. Roots pumps or blowers are frequently used in series with roughing pumps allowing the rotors to freewheel as the gas is initially drawn through from the chamber on the way to the roughing pumps. As the pressure in the system drops, the efficiency of the roughing pumps falls off. At this point, the roots pump is then powered to increase the rotor speed, and this increases the output pressure, which becomes the supply pressure for the roughing pumps, bringing them back into their more efficient operating range. Turbomolecular pump is a high vacuum pump that uses a shaft rotating at high speed with a series of multibladed rotors on the shaft. The rotors alternate with multibladed stators. Cryopumps work by compressing helium using a compressor that can be air or water cooled and then allowing the helium to expand to cool down a surface within the system that acts as a condensation pump.