CHAPTER 4
REDUCTION GEARS AND RELATED
EQUIPMENT
This chapter contains information on the
operation, care and maintenance of reduction
gears and related equipment found on Navy ships.
All EN1s and ENCs must be familiar with the
design and construction details of naval reduction
gears and related equipment. When more detailed
information is needed, refer to the manufacturer’s
technical manual.
REDUCTION GEARS
The main reduction gears are the largest
and most expensive single units of machinery
found in the engineering department. When the
main reduction gears are installed properly and
are operated properly they give years of satisfac-
tory service. However, when casualties occur to
the main reduction gears they put any ship out
of operation or force it to operate at reduced
speed. Main reduction gear repairs are very
costly. Usually they must be accomplished by a
shipyard.
FACTORS AFFECTING GEAR
OPERATION
Proper lubrication is essential for the efficient
operation of reduction gears. This includes
supplying the proper amount of oil to the gears
and bearings, and keeping the oil clean and at
the proper temperature. All abnormal noises and
vibrations must be investigated and corrective
action must be taken immediately. Gears and
bearings must be inspected in accordance with cur-
rent instructions issued by NAVSEA, the type
commander, or other proper authority.
Lubrication of Gears and Bearings
The correct quantity and quality of lubricating
oil must be available at all times in the main sump.
This oil must be clean and it must be supplied to
the gears and bearings at the pressure specified
by the manufacturer. In order to supply the
proper quantity of oil, several conditions must be
met. The lubricating oil pump must deliver the
proper discharge pressure, and all relief valves in
the lubricating system must be set to function at
their designed pressure. Too small a quantity of
oil will cause the bearing to run hot. On the other
hand if too much oil is delivered to the bearing,
the excessive pressure will cause the oil to leak at
the seal rings, and may also cause the bearing to
overheat.
Lubricating oil must reach the bearing at the
proper temperature. If the oil is too cold, there
will be insufficient oil flow. If the oil supply is
too hot, some lubricating capacity is lost. For
most main reduction gears, the normal
temperature of oil leaving the lube oil cooler
should be between 120°F and 130°F. For full
power operation, the temperature of the oil leav-
ing the bearings should be between 140°F and
160°F. The maximum temperature rise of oil
passing through any gear or bearing, under any
operating condition, should not exceed 50°F, and
the final temperature of the oil leaving the gear
or bearing should not exceed 180°F. Temperature
rise and limit may be monitored by a thermometer
or by a resistance temperature element installed
where the oil is discharged from the bearings.
Cleanliness of lubricating oil cannot be
overstressed. The oil must be free from such
impurities as water, grit, metal, and dirt. Par-
ticular care must be taken to remove metal flakes
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