on each face of the piston is balanced.
Removing the oil signal from the valve rod
actuator stops motion in the valve rod and the
hub servomotor. The self-centering feature of the
servomotor over the regulating valve pin provides
the restoring force to counteract any
hydrodynamic tendency to change pitch from that
set by the command signal.
The inspections mentioned here are the
minimum requirements for reduction gears.
Where defects are suspected, or operating condi-
tions so indicate, inspections should be made at
more frequent intervals.
No inspection plates or other fittings of the
main reduction gear may be opened without the
permission of the engineer officer. Before replac-
ing of an inspection plate, connection, fitting, or
cover which permits access to the gear casing,
make a careful inspection to ensure that no
foreign matter has entered or remains in the cas-
ing or oil lines. An entry of the inspections, and
the name of the CPO or officer who witnesses the
closing of the inspection plate, should be made
in the Engineering Log.
The PMS requirements discussed in this sec-
tion are general in scope. Inspection requirements
for your ship are listed in the ships PMS Manual
and should be referred to for all maintenance
Gears should be jacked DAILYAT
ANCHORso that the main gear shaft is
moved 1 1/4 revolutions. This jacking should be
done with lubricating oil circulating in the system.
You should take the following actions
1. Sound with a hammer the holding down
bolts, ties, and chocks to detect signs of loosen-
ing of casing fastenings.
2. Open inspection plates, inspect gears, and
oil-spray nozzles. Wipe off oil at different points
and note whether the surface is bright or if already
corroded, and whether or not new areas are
3. Inspect the strainers for the oil-spray
nozzles to see that dirt or sediment has not
accumulated in them.
4. Take and record all main thrust bearing
When conditions warrant or if trouble is
suspected, a work request should be submitted to
a naval shipyard to perform a 7-YEAR INSPEC-
TION of the main reduction gears. This inspec-
tion includes clearance readings of bearings and
journals; alignment checks and readings; and any
other inspections, tests, or maintenance work that
may be considered necessary.
If the ships propeller strikes ground or a
submerged object, a careful inspection should be
made of the main reduction gear immediately
following the OCCURRENCE of the casualty. In
this inspection, the possible misalignment of the
bull gear and its shaft should be considered.
Where practicable, a naval shipyard should be re-
quested to check the alignment and concentricity
of the bull gear.
NAVAL SHIPYARD OVERHAUL
During a naval shipyard overhaul, the fol-
lowing work should be performed: inspection of
the condition and clearance of thrust shoes to en-
sure proper position of gear; inspection of the
thrust collar, nut, and locking device; and inspec-
tion of the flexible couplings between turbines and
reduction gears and removal of the sludge
FULL POWER TRIALS
The correction of any defect disclosed by
regular tests and inspections, and the conscien-
tious observance of the manufacturers instruc-
tions, should assure that the gears are ready for
full power at all times.
It is not advisable to open up gear cases,
bearings, and thrusts immediately BEFORE
TRIALS. In addition to the inspections which
may be directed by proper authority which are
conducted during the FULL POWER TRIALS,
the following checks must be made AFTER
TRIALS. Open the inspection plates, and examine
the tooth contact and the condition of the teeth
to note changes that may have occurred during
Chapter 4REDUCTION GEARS AND RELATED EQUIPMENT