Horizontal Multistage Centrifugal Pump in ring-section design, long-coupled or close-coupled, with axial or radial suction nozzle, cast radial impellers and motor-mounted variable speed system. Multistage pumps are defined as pumps in which the fluid flows through several impellers fitted in series. The head of a single-stage centrifugal pump is largely governed by the type of impeller and the circumferential speed. If the rotational speed cannot be increased due to other operating conditions and a larger impeller diameter would lead to very low specific speeds resulting in uneconomical efficiencies, fitting several stages in series can be an economic option of increasing the head. If the number of stages is altered at unchanged dimensions and speeds, the flow rate of such a multistage pump remains constant while the power input and head increase proportionally to the number of stages. This type of pump is often used in power station applications, e.g. as a boiler feed pump and in industrial applications requiring high pressures.