centrifugal force is developed to throw the liquid
outward and away from the center of rotation. Thus the
liquid is sucked in at the center, or eye, of the impeller
(center of rotation) and discharged at the outer rim of
the impeller.
The centrifugal pump, like the diaphragm pump, is
driven by a single-cylinder, four-cycle, air-cooled
gasoline engine. To operate the engine properly, you
should be familiar with its controls.
NOTE: Refer to the operator’s manual for specific
instructions for the type of pump you are operating.
OPERATION.— The operation of centrifugal
pumps is generally similar to the operation of diaphragm
pumps. Centrifugal pumps (fig. 14-34) are also fitted
with stuffing boxes and various types of bearings that
require periodic operator’s maintenance and inspection.
Figure 14-34.—Centrifugal pump.
NOTE: Unlike positive displacement pumps, the
discharge stop valve on centrifugal pumps must be
closed before starting the pump.
The reason for closing the stop valve is to allow the
pump to work against the sealed discharge and buildup
an effective pressure head before attempting to move
and distribute the liquid downstream. After the pump is
up to speed and the discharge valve is opened, it will
continue to maintain that pressure head unless the
operating conditions change.
There is no danger of building excessive pressure
while the pump is running with the discharge closed. If
the centrifugal pump were permitted to continue
operation with the discharge sealed, it would simply
build up toward its maximum discharge pressure and
then begin to churn the liquid; that is, the discharge
pressure would overcome the suction pressure and the
liquid would continually slip back to the suction side of
the pump. Nothing more would happen, except that the
pump would build up heat since the liquid would not be
able to carry away heat generated by the moving parts.
INSPECTION.— There is little for you to inspect
other than routine operator’s maintenance.
If you
follow all of the operator’s manual instruction and the
pump does not function properly, call for a field
mechanic or turn it in to the dispatcher with a hard card
for repair.
SWEEPERS
Many different types of sweepers are used in the
Navy.
Some of the most common are the towed
sweeper, the street sweeper, and the magnetic sweeper.
Figure 14-35.—Towed sweeper.
14-30
