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

CLEARANCE

RINGS

PACKING

AUTO-LUBE