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 TM 5-685/NAVFAC MO-912
CHAPTER 8
LUBRICATING OIL PURIFICATION
8-1. Purification systems.
cally neutral, highly absorbent material. Cotton,
cellulose waste, or paper is usually used as the
Oil purification systems, either in the engine pres-
absorbent filtering material. The filter tank is pro-
sure system or oil supply system are classified by
vided with necessary entry and exit ports, internal
the method of flow used' in purifying the oil. The
tubing (perforated and solid), check valves and ori-
systems frequently used are the bypass and full-
fices to ensure proper flow of the oil through the
flow types as follows:
filtering material. Filters are more efficient than
a. In the bypass system part of the total oil circu-
strainers in removing very small particles and are
lating in the engine passes through the filter or
usually designed to process strained oil. Refer to the
purifying equipment. The system continuously
filter manufacturer's literature for details and ser-
cleans a small portion of the oil and, in general,
vicing instructions.
removes contaminants as fast as they are formed in
(2) Chemically actiuated. Absorbent filters con-
the engine. Thus, new oil may deteriorate but will
tain chemically activated material instead of chemi-
gradually stabilize when the effectiveness of the
cally neutral material. Construction of absorbent-
filtration system matches the rate of production of
type and adsorbent-type filters is similar. The
contaminants.
filtering materials include charcoal, clay and fuller's
b. In the full-flow system all of the oil circulating
earth. These materials remove water, acidic compo-
in the engine passes through filtering equipment
nents, and may absorb certain light petroleum ele-
prior to going to the engine.
ments, waxes or residual products. They usually
accomplish good purification and may reduce acid-
8-2. Forms of contamination.
ity as well as remove the solid contaminants. Absor-
bent or adsorbent filters may be used on straight
Refer to appendix C paragraph C-le(2) for informa-
run, uncompounded mineral oils where there is no
tion on complete sample testing. Oil contamination
danger of removing essential additives. Absorbent
usually occurs in one of two forms, as follows:
filters (chemically-neutral filters) should be used in
conjunction with compounded or additive-type oil.
other solid matter entering the oil.
Refer to the filter manufacturer's literature for de-
b. Undesirable substances such as water, poly-
tails and servicing instructions. Ensure that the
merized products of oil breakdown, acids and other
filtering system complies with the engine manufac-
chemical matter entering the oil.
turer's recommendations.
8-3. Methods of purifying.
c. Centrifuging. An oil purification centrifuge
usually consists of a stationary bowl that encloses a
Oil purification is accomplished by the use of one, or
rotating element. The element, mounted on a verti-
any combination, of the following methods: strain-
cally arranged axis, rotates at a high speed within
ing, filtering, centrifuging, or reclaiming.
the bowl. High-speed rotation causes a column of oil
a. Straining. The usual type of oil strainer can be
to form in the portion of the element nearest the
woven wire screen or perforated sheet metal. Edge-
center and a column of water to balance this at the
type and wire-wound strainers are also used. The
outer edge of the centrifuge bowl. Solid particles
edge-type consists of stacks of metal discs separated
having a gravity value heavier than that of the oil
by thin washers. The wire-wound type consists of a
are thrown outward, and the heavy solids accumu-
spool wrapped with finely serrated wire forming a
late in the centrifuge bowl. Water is removed by the
clearance between adjacent wires. Strainers are de-
high gravity differential produced by the high speed
signed to remove solid particles from the oil, usually
of the centrifuge. Effective mechanical separation
between 0.0015 and 0.003 inches in size, depending
occurs; however, materials in a suspended state are
on the engine manufacturer's specifications. Refer
not always removed by this method. Chemical con-
to the strainer manufacturer's literature for details
taminants are separated only if they have a mark-
and servicing instructions.
edly different specific gravity from that of the oil.
b. Filtering. Filtering is accomplished using
Polymerized products having a gravity similar to
chemically neutral or chemically activated filtering
that of oil are not separated and, in general, fuel oil
material.
dilution is not affected or corrected. The centrifuge
(1) Chemically neutral. The oil filter usually
is used extensively in fuel oil purification but has
consists of a canister or tank containing a chemi-
8-1
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