Hale RSD - Manual (Page 15)

15 Section 2: Introduction
Hale Products, Inc., Nov. 2005, Rev-A
In tro d u ctio n
❑
2 Introduction
2.1 PRINCIPLES OF OPERATION
Centrifugal Force
Hale pumps are centrifugal pumps that operate on the principle of centrifu-
gal force created by a rapidly spinning disk. (See Figure 2-1: “Centrifugal
Force - Rotating Disk.”)
As the disk rotates, it throws water from the center
toward the outer circumference of the disk. The
velocity at which the water travels from the center
directly relates to the diameter of the disk and the
speed of rotation.
When water is confined in a closed container, such
as the volute (pump body), the velocity of the water
is converted to pressure that rises to a level depen-
dent on the speed of rotation.
There are three interrelated factors that regulate
the performance of a centrifugal pump:
❑ SPEED (RPM) If the speed of rotation
increases with flow held constant, fluid pressure increases.
❑ PRESSURE If pressure changes with speed held constant, the flow,
measured in gallons or liters per minute (GPM/LPM), changes inversely;
if pressure increases, flow decreases. Pressure is measured in pounds
per square inch (PSI) or BAR.
❑ FLOW If the pressure is held constant, the flow increases with an
increase in the speed of rotation. Flow is measured in the number of gal-
lons of fluid per minute (GPM/LPM) that a pump can deliver when sup-
plied from draft.
A centrifugal pump is preferred by the fire protection service due to its ability
to fully utilize any positive suction inlet pressure, reducing the amount of
work done by the pump.
For example, if the required discharge pressure is 120 PSI (8.3 BAR) and
the inlet pressure is 45 PSI (3.1 BAR), the pump must only produce the dif-
ference in pressure or 75 PSI (5.2 BAR).
Figure 2-1: Centrifugal
Force - Rotating Disk