Page 61 - Know and Understand Centrifugal Pumps

Useful Wo

and Pump

Efficiency

Useful work from a pump

The physicist James Watt is honored in the electrical community for the
term ‘watt’. He made various advancements and improvements to
stationary boilers and steam engines. It is said that the first practical use
of the steam engine was in raising (call it pumping) water out of the
coalmines. Almost all mines would flood if the water were not pumped
from the bilge, out of the mine. Before the steam engine, the miners
used children and horses to lift and carry the bilge water.
James Watt developed the terms of energy, work, and power. He
defined the following:

Energy is the capacity to perform work. Example; I have the energy
in my bicep muscle to lift a 100-pound weight.
Work is a force multiplied over a distance. Example: If I lift a 5-
pound weight one foot into the air, then I’ve performed 5 foot-
pounds of work.
Power is work performed within a certain specified time frame.
Power is when I perform 5 foot-pounds of work within a second, or
minute.

Many people conhse these terms, but they actually have precise
definitions. If I should lift 10 pounds a distance of 10 feet, then I’ve
performed 100-foot-pounds of work (10 pounds x 10 feet = 100).
Before the steam engine, the most powerhl force to perform work, or
exert a force, was a horse.
James Watt, with actual tests, determined that a coal mine draft horse
could lift 550 pounds, a distance of one foot, within a second. So,
James Watt declared 550 foot-lbs/sec. to be one Horsepower. To this
day, this has become the standard definition of a horsepower (1 HI’ =

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