ABSTRACT
Pumps can be categorized into two major groups, namely, gas transfer pumps and capture pumps. Transfer pumps can be classified into subcategories of displacement pumps and kinetic pumps. In the category of displacement pumps, the chapter discusses piston oil pumps; single-rotor pumps such as rotary oil pumps, rotary water ring pumps, dry piston pumps, dry rotary pumps, dry diaphragm pumps and scroll pumps; and then two-rotor pumps including Roots pumps and claw/hook pumps; and screw pumps. Kinematic pumps operate on the principles of transfer momentum from fast moving surfaces to molecules. Kinematic pumps are also those whose fluid jets or molecular beams transfer their momentum to molecules of the pumped gases. Such pumping media are employed in jet fluid pumps, particularly ejector and diffusion pumps. Gas molecules are also removed from the vacuum system by trapping them on cold and chemically active surfaces. Chemical sorption based on getters can be assisted by electric pumping.
