Function of feed pump in a boiler feed system / steam turbines
The feed pump raises the feedwater
The feed pump raises the feedwater to a pressure high enough for it to
enter the boiler.
For auxiliary boilers, where small amounts of feedwater are pumped,
a steam-driven reciprocating positive displacement pump may be used.
Another type of feed
pump often used on package boiler installations is known as an 'electro
feeder'. This is a multi-stage centrifugal pump driven by a constant speed
electric motor. The number of stages is determined by the feed
quantity and discharge pressure.
Steam turbine-driven feed pumps are usual with high-pressure
watertube boiler installations. A typical turbo-feed pump is shown in
Figure above. The two-stage horizontal centrifugal pump is driven by an
impulse turbine, the complete assembly being fitted into a common
The turbine is supplied with steam directly from the boiler and
exhausts into a back-pressure line which can be used for feed heating.
The pump bearings are lubricated by filtered water which is tapped off
from the first-stage impeller. The feed discharge pressure is maintained
by a governor, and overspeed protection trips are also provided.
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