in figure 7-16, view D. Wider spaces are checked
seawater by centrifugal force. Water, how-
with a piece of square key stock and a thickness
ever, can be separated from lube oil because
gauge.
water and lube oil are immiscible (incapable
of being mixed). Furthermore, there must
be a difference in the specific gravities of
the materials before they can be separated by
PURIFIERS
centrifugal force.
Detailed instructions are furnished with each
When a mixture of lube oil, water, and
purifier concerning its construction, operation,
sediment stands undisturbed, gravity tends to
and maintenance. When you are responsible for
form an upper layer of lube oil, an intermediate
the operation and maintenance of a purifier, study
layer of water, and a lower layer of sediment.
the appropriate manufacturer's technical manual
The layers form because of the specific gravities
and follow the instructions carefully. In the
of the materials in the mixture. If the lube
oil, water, and sediment are placed in a
following section we will discuss general informa-
tion on the methods of purification and the
container that is revolving rapidly around a
vertical axis, the effect of gravity is negligible
principles of operation of centrifugal purifiers.
in comparison with that of the centrifugal
Centrifugal purifiers are used for purification of
force. Since centrifugal force acts at right
both lube oil and fuel. However, since the
angles to the axis of rotation of the container,
principles are the same for both, we will discuss
the sediment with its greater specific gravity
lube oil only.
assumes the outermost position, forming a
layer on the inner surface of the container.
A purifier may remove both water and
Water, being heavier than lube oil, forms an
sediment, or it may remove sediment only.
When water is involved in the purification
intermediate layer between the layer of sediment
process, t h e purifier is usually called a
and the lube oil, which forms the innermost
SEPARATOR. When the principal contaminant
layer. The separated water is discharged as
i s dirt or sediment, the purifier is used
waste, and the lube oil is discharged to the
as a CLARIFIER. Purifiers are generally used
sump. The solids remain in the rotating unit.
as separators for the purification of fuel.
When used for purification of a lube oil, a purifier
Separation by centrifugal force is further
may be used as either a separator or a clarifier.
affected by the size of the particles, the viscosity
Whether a purifier is used as a separator or a
of the fluids, and the time during which the
clarifier depends on the water content of the
materials are subjected to the centrifugal force.
oil that is being purified.
In general, the greater the difference in specific
gravity between the substances to be separated and
The following general information will help
the lower the viscosity of the lube oil, the greater
you understand the purification process, the
will be the rate of separation.
purposes and principles of purifier operation, and
the basic types of centrifugal purifiers in use in
naval service.
PURIFIER CLASSIFICATION
Two basic types of purifiers are used in
PURIFIER OPERATION
Navy installations. Both types use centrifugal
force. Principal differences in these two machines
In the purification of fluid, centrifugal
exist, however, in the design of the equip-
force is the fundamental principle of opera-
ment and the operating speed of the rotating
tion. A centrifugal purifier is essentially a
elements. In one type, the rotating element
container that is rotated at high speed while
is a bowl-like container that encases a stack
of discs. This is the disc-type DeLaval purifier,
contaminated lube oil is forced through, and
which has a bowl operating speed of about
rotates with, the container. However, only
materials that are in the lube oil can be
7,200 rpm. In the other type, the rotating
separated by centrifugal force. For example,
element is a hollow cylinder. This machine
JP-5 or naval distillate cannot be separated
is the tubular-type Sharples purifier, which
has an operating speed of 15,000 rpm.
from lube oil, nor can salt be removed from
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