CENTRIFUGAL PUMP CLASSIFICA-
which you are primarily concerned are used
TION.--Centrifugal pumps may be classsified in
for such purposes as
several ways. For example, they maybe either
single-stage or multistage. A single-stage pump
providing fuel oil to the GTE,
has only one impeller; a multistage pump has two
or more impellers housed together in one casing.
circulating lubricating (lube) oil to the
In a multistage pump, each impeller usually acts
separately, discharging to the suction of the next-
stage impeller. Centrifugal pumps are also
supplying seawater for the coolers in
classified as horizontal or vertical, depending on
engineering spaces,
the position of the pump shaft.
Impellers used in centrifugal pumps may be
pumping out the bilges, and
classified as single-suction or double-suction,
depending on the way in which liquid enters the
transferring fuel oil to various storage and
eye of the impeller. Figure 7-2 shows single-
service tanks.
suction and double-suction arrangements of
centrifugal pump impellers. The single-suction
CIASSIFICATION OF PUMPS
impeller (view A) allows liquid to enter the
eye from one side only; the double-suction
Pumps aboard ship outnumber all other
impeller (view B) allows liquid to enter the
auxiliary machinery units. They include such types
eye from both sides. The double-suction arrange-
as centrifugal, rotary, and jet pumps. In the
ment has the advantage of balancing the end
following section we discuss these different pumps
thrust in one direction with the end thrust in the
and their application to the engineering plant.
other direction.
Impellers are also classified as CLOSED or
OPEN. A closed impeller has side walls that
Centrifugal Pumps
extend from the eye to the outer edge of the vane
tips; an open impeller does not have side walls.
Aboard gas turbine ships, centrifugal pumps
Most centrifugal pumps used in the Navy have
of various sizes are driven by electric motors to
closed impellers.
move different types of liquid. The fire pump and
seawater service pump are two examples of this
CONSTRUCTION--As a rule, the casing for
type of pump.
the liquid end of a pump with a single-suction
A basic centrifugal pump has an impeller
impeller is made with an end plate that can be
keyed to a drive shaft, which is rotated by an
removed for inspection and repair of the pump.
electric motor. The drive shaft is fitted inside a
A pump with a double-suction impeller is
casing which has a suction inlet and a discharge
generallv made so one-half of the casing may be
our let. Figure 7-1 shows the arrangement of
lifted without disturbing the pump.
components in a centrifugal pump.
Figure 7-1.--Centrifugal pump
7-2
