The speed at which a pump is operated is a matter of more or less
importance, according to its widely varying conditions. In all
calculations regarding the capacity of a pump the regularity with which
it makes its “stroke” is taken into consideration; the uniformity of
the supply of water to a boiler is always a subject of anxiety to the
attendant. The capacity of a pump is usually determined by its number
of strokes in a given time, hence the need of a pump regulator or
governor.
[Illustration: FIG. 566.]
The governor is not only intended to maintain a uniform water pressure
in the mains, but to prevent the pump from racing whenever a greater
quantity of water is demanded than the pump is capable of delivering,
as in the case of bursted mains or hose, or any other contingency
whereby the pressure upon the discharge pipe is suddenly relieved.