HALE AP, Техническое руководство

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There are three interrelated factors that regulate the performance of a centrifugal pump:
Speed (RPM):
If the speed of rotation increases with the flow held constant, the water pressure increases.
Pressure:
Pressure is usually expressed in psi or bar. If pressure changes and speed is constant, the flow
will change inversely (if pressure increases, flow decreases).
Flow:
Flow is usually expressed in gpm or Lpm that a pump can deliver when supplied from draft. If the
pressure is held constant, the flow will increase with an increase in the speed of rotation.
The centrifugal pump is preferred by the fire protection service due to its ability to fully utilize any
positive inlet pressure, reducing the strain on the pump.
For example, if the required discharge pressure is 120 psi (8 bar), and the inlet pressure is
45 psi (3 bar), the pump must only produce the difference in pressure of 75 psi (5 bar). This con-
tributes to low engine and pump speeds which reduces wear on the pump. Another important
benefit is the centrifugal pump has basically only two moving parts; the impeller and the shaft.
As shown on Figure 2, during operation water enters the suction eye of the impeller (intake). The
rotating impeller vanes develop discharge pressure and direct the water to the discharge open-
ing. The cutwater is a wedge that divides the water between the volute (a single chamber diffus-
er) and the pump discharge.
Figure 2. Single Stage Water Flow
2.4.1 Explanation Of Terms
The following major terms are explained in sufficient detail to allow a maintainer to communicate
pumping issues or troubles with Hale Customer Service personnel. As a basic understanding of
the terms (and the principles associated with them) will assist operators (for both operations and
maintenance purposes) utilize common terminology and understand accepted principles when
communicating among each other.
2.4.1.1
Atmospheric Pressure (Static Air Pressure)
Air pressure is 14 pounds (AKA psi) at sea level. Pressure increases below sea level and de-
creases above sea level due to the increased or decreased volume of air pushing down at that
height. In addition to the amount of air, weather also effects air pressure. Air in a high pressure