PURIFIER OPERATION
Centrifugal force is the fundamental operating
principle used in the purification of fluid. Centrifugal
force is that force exerted on a body or substance by
rotation. Centrifugal force impels the body or substance
out ward from the axis of rotation.
Essentially, a centrifugal purifier is a container
rotated at high speed. As it rotates, contaminated lube
oil is forced through, and rotates with, the container.
Only materials that are in the lube oil are separated by
centrifugal force. For example, water is separated from
lube oil because water and lube oil are immiscible,
which means they are incapable of being mixed. Also,
there must be a difference in the specific gravities of the
materials before they can be separated by centrifugal
force. You cannot use a centrifugal purifier to separate
JP-5 or naval distillate from lube oil because it is capable
of being mixed; likewise, you cannot remove salt from
seawater by centrifugal force.
When a mixture of lube oil, water, and sediment
stands undisturbed, gravity tends to form an upper layer
of lube oil, an intermediate layer of water, and a lower
layer of sediment. The layers form because of the
specific gravities of the materials in the mixture. If the
lube oil, water, and sediment are placed in a container
that is revolving rapidly around a vertical axis, the effect
of gravity is negligible in comparison with that of the
centrifugal force. Since centrifugal force acts at right
angles to the axis of rotation of the container, the
sediment with its greater specific gravity assumes the
outermost position, forming a layer on the inner surface
of the container. Water, being heavier than lube oil,
forms an intermediate layer between the layer of
sediment and the lube oil, which forms the innermost
layer. The separated water is discharged as waste, and
Figure 10-33.—Disc-type centrifugal purifier.
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