Hale DSD User Manual
Page 5
BASIC PARTS OF A HALE Midship CENTRIFUGAL PUMP
Figure. 1-2 shows the basic parts of a Hale midship centrifugal pump. These parts are briefly
described in the following text
Impeller
The impeller provides velocity to the water. This part is mounted on a shaft that is rotated by
the drive. Water enters the rotating impeller at the intake (or eye), and is confined by the
shrouds and the vanes mounted in the impeller to build pressure The vanes guide water from
the inlet to the discharge and reduce the turbulence of the spinning water. Vanes curve away
from the direction of rotation so water moves toward the outer edge. The shrouds form the
sides of the impeller and keep the water confined to centrifugal acceleration.
Figure 1-3 traces a drop of water from the intake of the impeller to the discharge outlet The
impeller is mounted so that the discharging tribe is widest at the pump outlet. The increasing
discharge path, known as the volute, collects the water at a constant velocity. A further
increase in pressure and a decrease in velocity takes place in the diffuser.
Figure 1-3. Impeller Operation
Clearance Rings
Clearance rings prevent the water that is pressurized and leaving the pump volute from
returning to the intake of the impeller. Centrifugal pumps have clearance rings at the impeller
intake to prevent leakage. This is accomplished by limiting the radial clearance between the
spinning impeller and the stationary clearance ring. Refer to Figure 1-2.
A clearance ring usually has a radial clearance of about 0.0075-inch per side, or a 0.015-inch
diameter. However, the clearance will increase over time as the pump is operated. Wear is due to
foreign material found in the water. Clearance rings are designed for replacement as the clearance
increases from usage and wear.
If a pump is operated without water for extended periods or without discharging water, it may
overheat. This may damage the pump and the drive mechanism.
IMPELLERS
(TWO STAGE)
SLEEVE BEARING
SLINGER RING
BALL BEARINGS
BALL BEARINGS
CLEARANCE
RINGS
PACKING
AUTO-LUBE