Pump, device used to raise, transfer, or compress liquids and gases. Four general classes of pumps for liquids are described below. In all of them, steps are taken to prevent cavitation (the formation of a vacuum), which would reduce the graham vacuum technology flow and damage the structure of the pump. Pumps used for gases and vapours are usually known as compressors steam ejector (see Air Compressor). The study of fluids in motion is called fluid atmospheric air injector dynamics (see Fluid Mechanics). Reciprocating pumps consist of a piston moving back and forth in a cylinder that has valves to regulate the flow of liquid into and out of the cylinder. These pumps may be single or double acting. In the single acting pump, the pumping action takes place on only one side of the piston, as in the case of the common lift pump, vacum solutions in which the piston is moved up and down by hand. In the double acting pump, dry pumps the pumping action takes place on both sides of the piston, as in the electrical or steam-driven boiler feed vane vacuum pump pump, in which water is supplied to a steam boiler under high pressure. These pumps can be single-stage or multi-staged. Multi-staged reciprocating pumps have multiple cylinders in series. See Steam Engine.
Also known as rotary pumps, centrifugal pumps have a rotating impeller, also known as a blade, that is immersed in the liquid. Liquid enters the pump near the axis of the impeller, and the rotating impeller sweeps the rotary piston pump liquid out towards the ends of the impeller blades at high pressure. The impeller also gives the liquid a relatively high velocity that can be converted into pressure in a stationary part of the pump, known as the diffuser. In high-pressure pumps, a number of impellers may be used in series, and the diffusers following each impeller may contain guide vanes to gradually reduce the liquid velocity. For lower-pressure pumps, the diffuser is generally a spiral passage, vacuum gas piston pumps known as a volute, with its cross-sectional area increasing gradually to reduce the velocity efficiently. The impeller must be primed before it can begin operation that is, the impeller must be surrounded by liquid ring vacuum pump liquid when the pump is started. This can be done by placing a checkvalve in the suction line, which holds the liquid in the pump when the impeller is not rotating. If this valve leaks, the pump may need to be primed by the introduction of liquid from an outside source such as the discharge reservoir. A centrifugal pump generally has a valve in the discharge line to control the flow and pressure.