7.6 Power Transmission - 7.6 Power Transmission Flashcards
Prime Mover(s) Engine(s)
Gas Turbines, Diesel, Steam Turbine
Main Reduction Gear (MRG)
Reduces High Speed/Low Torque into Low Speed/High Torque to drive the shaft/propeller
Shaft
Transmits power from the MRG to the propeller
Propeller
Fixed or Controllable Pitch Propeller (CPP)
Characterization of Steam & Gas Turbine MRG
Dual Input
Double reduction
Double helical
Locked train
Articulated
Characterization of Diesel (LSD/LPD) MRG
Dual Input
Single reduction
Double helical
Locked train
Articulated
Dual Input
Two points of power input from the turbines to the MRG
Locked Train
1st reduction pinion placed between a pair of 1st reduction gears
Balances tooth loading
Prevents “gear crawling”
Picture
Articulated
“Quill Shaft”
The gears and pinions are mounted on an outer shaft that “floats” and allows limited flexibility
The 1st reduction gear and 2nd reduction pinion outer shaft is mounted to an internal quill shaft
Bearings on each side of each gear vice only on the ends of the shaft
Accessory Drives/Connections
Attached Pump
Vent Fog Precipitator
Dehumidifier
Turning Gear
Tachometer
Shaft Brakes Assemblies
Clutches
MRG Lube Oil System Composition
1x Attached L/O Pump
2x Electric driven pump
Shell & tube type cooler
Duplex Strainer
L/O sight flow indicators
Oil must be >90o F prior to engaging jacking gear / normal operation
Prior to securing, lower lube oil temp 10-15o F (100o F min)
L/O Spray Nozzles
Forms a wide angle spray
Directed to gear mesh area
Provides cooling & lubrication
Turning Gear
Provides means to rotate components of the power train
Provides means to lock gears (and main shaft)
MRG Physical Security/Access
Placing OOC: CO
Physical Security:
Eng. Officer maintains key custody
If MRG is open, it requires permission and supervision
SSS Clutch (GT)
Synchronized Self-Shifting (SSS) clutch
Automatically engages and disengages the engine to the MRG
On the reduction gear input shaft prior to the 1st reduction pinion
Permits independent operation of the GTEs
Shafting System
Transfer torque generated by the main reduction gear to the propeller
Transmit the thrust developed by the propeller to the main thrust bearing
Main Thrust Bearing
Type:
Absorbs axial thrust transmitted through the shaft from the propeller
Location is specific to class of ship – 1 per shaft
Bulkhead Seal
Provides NO radial or axial support to the shaft
Allows for the shaft to traverse through bulkheads
Automatically sets a boundary between spaces due to pressure differentials (air or water)
Line Shaft Bearings
Provides radial support to the shaft
-Support the weight of the shaft to prevent it from sagging
Quantity based on length of shaft
Lubricated with 2190
-From its own sump
-Not part of the MRG L/O System
-“Without online purification”
-Remote temperature sensors
Stern Tube Seal
Maintain water tight integrity of the shaft traversing the hull
Includes an emergency inflatable seal; the shaft MUST be stopped and locked
Provides NO radial or axial support to the shaft
Stern Tube Bearings
Provides radial support to the shaft
Located aft of stern tube seal
Cooled and lubricated by seawater (stern tube seal & bearing)
-Provided by auxiliary seawater
-Flushing water used inport/shallow water
Split upper/lower shell
Made of bronze shell with phenolic strips
Strut Bearing
Construction is similar to the stern tube bearing
Supports the end of the shaft radially
Cooled by seawater
No flushing water is provided by the ship
May be more than one strut bearing
Types of Propellers
Fixed Pitch Propellers - non-movable blades
CRP/CPP - Propellers with movable blades
CRP/CPP - Propellers with movable blades
CRP uses oil to move propeller blades
CRP System Oil:
High pressure oil to hub
Return oil from hub
Prairie air to hub (CG & DDG)
Runs through shaft center
Surrounded by valve control rod
Valve rod supported by spider assemblies
Controllable Reversible Pitch (CRP) System
CRP L/O Sump
CRP L/O Pumps
Hydraulic Oil Power Module (HOPM)
Oil Distribution Box (ODBox)
Propellers
