the lube oil is discharged to the sump. The solids remain
in the rotating unit.
Other factors that affect separation by centrifugal
force include the size of the particles, the viscosity of
the fluids, and the length of time the materials are
subjected to centrifugal force. Generally, the greater the
difference in specific gravity between the substances to
be separated and the lower the viscosity of the lube oil,
the greater the rate of separation.
Two basic types of purifiers are used in Navy
installations, and both types use centrifugal force. There
are principal differences in the equipment design and
operating speed of the rotating elements of the two
machines. In one type, the rotating element is a
bowl-like container that encases a stack of discs. This is
the disc-type DeLaval purifier, which has a bowl
operating speed of about 7,200 rpm. In the other type,
the rotating element is a hollow cylinder. This machine
is the tubular-type Sharples purifier, which has an
operating speed of 15,000 rpm.
Figure 10-33 shows a cutaway view of a disc-type
centrifugal purifier. The bowl is mounted on the upper
end of the vertical bowl spindle, and driven by a worm
wheel and friction clutch assembly. A radial thrust
bearing at the lower end of the bowl spindle carries the
weight of the bowl spindle and absorbs any thrust
created by the driving action. Figure 10-34 shows the
parts of a disc-type bowl. The flow of fluid through the
bowl and additional parts are shown in figure 10-35.
Contaminated fluid enters the top of the revolving bowl
through the regulating tube. The fluid then passes down
the inside of the tubular shaft, out the bottom, and up
into the stack of discs. As the dirty fluid flows up through
the distribution holes in the discs, the high centrifugal
force exerted by the revolving bowl causes the dirt,
sludge, and water to move outward. The purified fluid
is forced inward and upward, discharging from the neck
of the top disc. The water forms a seal between the top
disc and the bowl top. (The top disc is the dividing line
between the water and the fluid.) The discs divide the
space within the bowl into many separate narrow
passages or spaces. The liquid confined within each pass
is restricted so that it flows only along that pass. This
arrangement minimizes agitation of the liquid passing
through the bowl. It also forms shallow settling
distances between the discs.
Any water separated from the fluid, along with
some dirt and sludge, is discharged through the
discharge ring at the top of the bowl. However, most of
the dirt and sludge remains in the bowl and collects in a
more or less uniform layer on the inside vertical surface
of the bowl shell.
A cutaway view of a tubular-type centrifugal
purifier is shown in figure 10-36. This type of purifier
consists of a bowl or hollow rotor that rotates at high
speeds. The bowl has an opening in the bottom to allow
the dirty fluid to enter. It also has two sets of openings
Figure 10-34.Parts of a disc-type purifier bowl.