on each face of the piston is balanced.Removing the oil signal from the valve rodactuator stops motion in the valve rod and thehub servomotor. The self-centering feature of theservomotor over the regulating valve pin providesthe restoring force to counteract anyhydrodynamic tendency to change pitch from thatset by the command signal.INSPECTIONSThe inspections mentioned here are theminimum requirements for reduction gears.Where defects are suspected, or operating condi-tions so indicate, inspections should be made atmore frequent intervals.No inspection plates or other fittings of themain reduction gear may be opened without thepermission of the engineer officer. Before replac-ing of an inspection plate, connection, fitting, orcover which permits access to the gear casing,make a careful inspection to ensure that noforeign matter has entered or remains in the cas-ing or oil lines. An entry of the inspections, andthe name of the CPO or officer who witnesses theclosing of the inspection plate, should be madein the Engineering Log.PMS INSPECTIONSThe PMS requirements discussed in this sec-tion are general in scope. Inspection requirementsfor your ship are listed in the ship’s PMS Manualand should be referred to for all maintenanceaction.Gears should be jacked DAILY—ATANCHOR—so that the main gear shaft ismoved 1 1/4 revolutions. This jacking should bedone with lubricating oil circulating in the system.You should take the following actionsQUARTERLY:1. Sound with a hammer the holding downbolts, ties, and chocks to detect signs of loosen-ing of casing fastenings.2. Open inspection plates, inspect gears, andoil-spray nozzles. Wipe off oil at different pointsand note whether the surface is bright or if alreadycorroded, and whether or not new areas areaffected.3. Inspect the strainers for the oil-spraynozzles to see that dirt or sediment has notaccumulated in them.4. Take and record all main thrust bearingreadings.When conditions warrant or if trouble issuspected, a work request should be submitted toa naval shipyard to perform a 7-YEAR INSPEC-TION of the main reduction gears. This inspec-tion includes clearance readings of bearings andjournals; alignment checks and readings; and anyother inspections, tests, or maintenance work thatmay be considered necessary.If the ship’s propeller strikes ground or asubmerged object, a careful inspection should bemade of the main reduction gear immediatelyfollowing the OCCURRENCE of the casualty. Inthis inspection, the possible misalignment of thebull gear and its shaft should be considered.Where practicable, a naval shipyard should be re-quested to check the alignment and concentricityof the bull gear.NAVAL SHIPYARD OVERHAULDuring a naval shipyard overhaul, the fol-lowing work should be performed: inspection ofthe condition and clearance of thrust shoes to en-sure proper position of gear; inspection of thethrust collar, nut, and locking device; and inspec-tion of the flexible couplings between turbines andreduction gears and removal of the sludgedeposits.FULL POWER TRIALSThe correction of any defect disclosed byregular tests and inspections, and the conscien-tious observance of the manufacturers’ instruc-tions, should assure that the gears are ready forfull power at all times.It is not advisable to open up gear cases,bearings, and thrusts immediately BEFORETRIALS. In addition to the inspections whichmay be directed by proper authority which areconducted during the FULL POWER TRIALS,the following checks must be made AFTERTRIALS. Open the inspection plates, and examinethe tooth contact and the condition of the teethto note changes that may have occurred duringChapter 4—REDUCTION GEARS AND RELATED EQUIPMENT4-15
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