Sump Pumps and Multistage

These are a small single-stage vertical pumps used to drain shallow pits or sumps. They are of the same general construction as vertical process pumps but are not designed for severe operating conditions.

Multistage Centrifugal Pumps
These pumps are used for services requiring heads (pressures) higher than can be generated by a single impeller. All impeller are in series, the liquid passing from one impeller to the next and finally to the pump discharge. The total then is the summation of the heads of the individual impellers. Deep-well pumps, high pressure water supply pumps, boiler feed pumps, fire pumps, and charge pumps for refinery processes are example of multistage pumps required by various services.

Multistage pumps may be of the volute type, with single, or double suction impellers or of the diffuser type. They are have horizontally spilt casing or, for extremely high pressure, 20 to 40 MPa (3000 to 6000 lbf/in2), vertically split barrel type exterior casting with inner casing containing diffusers, interstage passage, ets.