Boiler feedwater pump

A feedwater pump (often referred to as a feed pump for short) is a pump used to supply a steam boiler or steam generator with feedwater needed to produce steam.

In steam power plants it is designed as a centrifugal pump. In larger power plants, a backing pump is connected upstream of the feed pump to provide the necessary upstream pressure. The feed pump is usually driven by its own smaller steam turbine, the so-called feed pump drive turbine or "spar" for short. The start-up and shut-down operation is performed by electric feed pumps "ESP". The power range of such pumps can be up to 42 MW in large power plants and is thus the largest single item of a steam power plant's own demand.

For safety reasons, each boiler must have at least two independently operating feed devices (for large systems, one turbo feed pump and two electric feed pumps).

For smaller steam plants (locomotives, steam cranes, smaller boiler plants) there are also piston pumps. These duplex pumps consist of two mechanically coupled pistons. The drive piston is driven by the steam pressure and moves the pump piston which delivers the feed water. The drive piston has a larger diameter than the pump piston. This allows the pump to generate a higher pressure than is supplied to it as drive pressure.

Another design, which used to be common on steam locomotives, among others, is the steam jet feed pump, a jet pump driven by steam.