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TM 5-685/NAVFAC MO-912
(7) Hot oil sump pump (return oil pump, filter
ing are provided for that changeover. The auxiliary
pump is generally used long enough to return the oil
pump) to force hot used oil through filtering and/or
purifier and cooler.
from the critical points and to check the pressure,
(8) Oil filter to remove suspended solids, dirt
temperature and flow sensors, indicators, and con-
and sludge.
trols to enable engine cranking. Pumps are usually
(9) Sampling valves for taking samples of oil
gear-type with pressure regulation. The engine-
and filter solids periodically for testing and analy-
driven pump speed is directly related to engine
sis.
speed so that oil flow increases as speed increases.
b. Types and operation. Large diesel engines use
(10) Transfer systems for adding new oil and
removing used oil from the engine lube system.
a lubrication system different from that of smaller
(a) Lube oil must have certain properties for
diesel engines. Because large engines require a
specific application. It must flow properly at the
large quantity of oil, a separate sump tank is in-
minimum temperatures (pour point), have proper
stalled to receive oil from the crankcase. The lubri-
viscosity (resistance to shear) between moving parts
cating oil pump draws oil from the sump tank
and retain desired viscosity over the range of tem-
through the strainers. Oil is then discharged, under
peratures in the engine (viscosity index). The oil
pressure, into the oil cooler.
must resist oxidation (stability) that forms gum and
(1) The oil then goes to a header, located on the
sludge and the associated catalytic effects of engine
engine, with branches leading to the various parts
metals present (especially copper and lithium) in
of the system. Leads extend from the header to each
the detergent additives. It must allow sludge par-
main bearing. After the oil has been supplied to the
ticles to disperse and not clump or deposit through-
main bearings, it passes through a drilled passage
out the engine. It will contain inhibitors to prevent
in the crank web. The oil then passes through a hole
oxidation, a dispersing agent and a detergent to
in the crank bearing journal to the connecting rod
keep surfaces clean.
bearing and up through a drilled hole in the con-
necting rod to the wrist pin. At the wrist pin, the oil,
(b) The physical specifications for crankcase
in some engines, passes through a spray nozzle for
lube oil are not positive indications of suitability.
splash lubrication against the underside of the pis-
The experience of the engine manufacturer is guid-
ton for cooling. The oil then drains down to the
ance for recommended oils. The user must choose.
engine crankcase and returns to the pump. Other
(c) Periodic sampling, analysis and evalua-
tion of results is important. An out-of-spec problem
branches from the header rnay supply oil to the gear
will be evident. It is also necessary to look for trends
trains, camshafts and bearings, rocker arms and
push rods, cylinder walls, turbo-chargers, blowers,
that warn of a condition that may become a major
and in some engines, to an oil-cooling system for
problem. An abnormal rise in the wear metals indi-
pistons. Engines may vary in many details, but the
cates abnormal wear. Increasing sulphur content
principles are the same in all.
and acidity indicates that the lube oil is being con-
taminated by high-sulfur fuel, oil blowby, etc.
(2) Lubricati ng systems of small engines usu-
ally are self-contained. The crankcase or a separate
(d) The lube oil tank must be sufficiently
oil pan underneath the engine contains all the oil
large to hold the oil required for the engine. It must
used in the system. Figure 3-8 is a cross section of a
be kept clean and closed to prevent contamination
diesel engine, showing lube oil flow.
of the oil. A vent with flame arrestor should exist.
c. Process. The diesel engine lubrication system
The tank is the reservoir that feeds the oil pumps.
The pump suction line should be above any possible
must circulate, filter, and cool large quantities of
sludge or water at the bottom. The tank and all the
lubricating oil. Figure 3-9 shows a schematic ar-
rangement of the main components of a diesel lubri-
components of the lube system should be of materi-
cation system. The arrows show the flow of lube oil
als that will not contaminate the oil.
through the system.
(e) Lube oil pumps circulate the oil at pres-
d. Oil storage. All high-speed engines and most
sure (5 to 75 psi depending on engine design and
system pressure losses when cold) through the oil
medium and low-speed engines use the crankcase
base or a sump integral with the crank-case for
feedline to the engine lube oil header. An auxiliary
storing lubricating oil. Several engines operate with
electrically-driven pump is used prior to starting a
a so-called dry crankcase to avoid crankcase oil fog
cold engine to provide warm oil to all points, espe-
that may cause excessive cylinder lubrication. Such
cially to heavily loaded main, crank, and wrist pin
engines must have an outside sump tank placed so
bearings, to make sure the lubricating film is
that oil from the crankcase will drain into it. One
formed at first movement. This auxiliary pump may
design has an elevated, closed pressure tank to
also serve as an automatic standby should a normal
which oil is pumped from the crankcase. Open,
engine-driven pump system fail. Controls and valv-
3-13





 


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