it to a given degree of purity. Decreasing the
spindle. The spindle is suspended from a ball bear-
viscosity of the oil by heating is one of the most
ing assembly. The bowl is belt-driven by an
effective methods of facilitating purification.
electric motor mounted on the frame of the
Even though certain oils may be satisfactorily
purifier.
The lower end of the bowl extends into a
purified at operating temperatures, a greater
flexibly mounted guide bushing. The assembly
degree of purification will generally result by
restrains movement of the bottom of the bowl,
heating the oil to a higher temperature. To
but it also allows the bowl enough movement to
accomplish this, the oil is passed through a heater,
where the proper temperature is obtained before
center itself during operation. Inside the bowl is
a device with three flat plates that are equally
the oil enters the purifier bowl.
spaced radially. This device is commonly referred
Oils used in naval ships may be heated to
specified temperatures without adverse effects,
to as the THREE-WING DEVICE, or just the
three-wing. The three-wing rotates with the bowl
but prolonged heating at higher temperatures
and forces the liquid in the bowl to rotate
is not recommended because of the tendency
at the same speed as the bowl. The liquid to be
of such oils to oxidize. Oxidation results
centrifuged is fed, under pressure, into the
in rapid deterioration. In general, oil should
bottom of the bowl through the feed nozzle.
be heated sufficiently to produce a viscosity of
After the bowl has been primed with water,
approximately 90 seconds Saybolt universal
separation is basically the same as it is in the disc-
(90 SSU).
type purifier. Centrifugal force causes clean fluid
Pressure should NEVER be increased above
normal to force a high-viscosity oil through the
to assume the innermost position (lowest specific
gravity), and the higher density water and dirt are
purifier. Instead, viscosity should be decreased by
forced outward towards the sides of the bowl.
heating the oil. The use of excess pressure to force
Fluid and water are discharged from separate
oil through the purifier will result in less efficient
openings at the top of the bowl. Any solid
purification. On the other hand, a reduction in
contamination separated from the liquid remains
the pressure that the oil is forced into the purifier
inside the bowl all around the inner surface.
will increase the length of time the oil is under
the influence of centrifugal force and will result
in improved purification.
GENERAL NOTES ON PURIFIER
The proper size discharge ring (ring dam) must
OPERATIONS
be used to ensure the oil discharged from a
For maximum efficiency, purifiers should be
purifier is free of water, dirt, and sludge. The size
operated at the maximum designed speed and
of the discharge ring used depends on the specific
rated capacity. Since reduction gear oils are
gravity of the oil being purified. All discharge
usually contaminated with water condensation,
rings have the same outside diameter, but have
inside diameters of different sizes.
the purifier bowls should be operated as
separators and not as clarifiers.
You should obtain specific details of operating
When a purifier is operated as a separator,
a given purifier from the appropriate instructions
PRIMING OF THE BOWL with fresh water is
provided with the unit. The information you have
been provided is general and applicable to both
essential before any oil is admitted into the
types of purifiers.
purifier. The water serves to seal the bowl and
to create an initial equilibrium of liquid layers.
If the bowl is not primed, the oil will be lost
through the water discharge port.
AIR COMPRESSORS
Several factors influence purifier operation.
The time required for purification and the out-
The air compressor is the heart of any
put of a purifier depend on such factors as the
compressed air system. It takes in atmos-
viscosity of the oil, the pressure applied to the oil,
pheric air, compresses it to the pressure
desired, and moves it into supply lines or
the size of the sediment particles, the difference
in the specific gravity of the oil, the substances
into storage tanks for later use. Air compressors
that contaminate the oil, and the tendency of the
come in different designs and configurations
oil to emulsify.
and have different methods of compression.
The viscosity of the oil will determine the
Some of the most common types used on
length of time required to purify the oil. The more
gas turbine ships will be discussed in this
chapter.
viscous the oil, the longer the time will be to purify
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