Hale DSD - Manual (Page 15)

PRIMING PUMP\
Priming pumps are used to create a vacuum; they are designed to evacuate air through the suction
hose and into the pump. The vacuum created allows atmospheric pressure to push water from the open
body of water through the suction hose and into the pump. Hale centrifugal midship pumps use Rotary
Vane Positive Displacement pumps for priming. A positive displacement pump moves a specified
amount of air or fluid with each revolution.
As shown in Figure 1-13, the priming pump has a single rotor mounted off-center (eccentric) to the
pump body housing. The vanes in the rotor slide in grooves and are held against the body housing by
centrifugal force. As a vane turns toward the discharge, it recedes into the rotor. As the rotor continues
past the discharge, the vane advances outward from its groove and against the body housing. During
this cycle, the space between the rotor and housing case fills with air, and the vanes, acting as wipers,
force air out of the discharge, creating a vacuum in the main pump allowing atmospheric pressure to
push water into the suction side of the main pump, filling it with water.
While the rotor draws air from the main pump, lubricant is pulled in from the lubricant tank This
lubricates the pump and the bearings and helps to create a better vacuum by scaling close tolerances in
the priming pump. The pump should not be operated unless the lubricant tank is filled
A Hale priming pump has a single control that both opens the priming valve between the midship pump
and the priming pump and starts the priming motor. The primer is automatically lubricated during
operation.
VANE
Figure 1-13. Priming System
HOUSING
ROTOR