An impeller pump is used to move a liquid through a piping system. This type of device is very common, and may be used in many different fluid system applications. Impeller pumps are excellent for use with liquids that contain impurities, such as solids, because they do not clog easily. Selecting the right impeller pump for a specific application is usually based on the type of fluid, flow rate, and operating conditions, such as temperature and pressure.
The main parts of an impeller pump are the housing or casing, the impeller mechanism, motor, and support bearings. The pump housing typically consists of a cavity that contains the moving parts of the pump while maintaining a liquid tight seal. A motor is used to rotate a shaft connected to the impeller inside the pump housing. The impeller mechanism is supported by the bearings. Most impeller pumps are electrically-powered, but units powered using air pressure or hydraulic fluid are also available.
The impeller mechanism generally consists of a short, cylindrical disc that contains one or more vanes, which may also be called blades, and a smaller diameter cylindrical drive shaft that is used to connect the impeller to a drive motor. When the impeller rotates, the vanes force liquid, in the radial direction, outward aganst the inside of the pump casing. Since the liquid is confined by the pump casing, the pressure of the fluid increases as it is forced outward against the inside surface of the pump cavity, and through the pump exit. The number of vanes on the impeller can range from one to greater than ten. For heavily soiled or solid-containing liquids, like sludge, sometimes only one vane is used.
An impeller pump can be purchased in a variety of diameters, ranging from less than 1/4 inch (0.6 cm), to greater than 10 feet (3 meters). These pumps operate at speeds ranging from below 30 to several thousands of revolutions per minute. Multi-stage impeller pumps can be purchased, in which the output of one unit is directed into another, thereby increasing the capacity and pressure capability. Several pumps can also be linked together in a series to increase the output and pressure of the fluid system.
The materials used to manufacture an impeller pump are usually based on the type of fluid it will be used with, and future operating conditions. For fluid systems that use water, aluminum or cast iron housings — with bronze or stainless steel internal components — are often used. For applications using fluids that are highly corrosive, or that operate at high temperatures or pressures, materials such as titanium, metal alloys, and other chemically-resistant materials are used, to ensure acceptable pump performance and life. Impeller pumps are also manufactured using plastics, usually for smaller scale applications that operate at lower flow and pressure conditions.