The vessel to which you are assigned is gear-driven with one main propulsion diesel engine and a fixed-pitch propeller. While underway, the main engine becomes disabled, requiring your vessel to be towed back into port. If pressurized lubricating oil is not available to the reduction gear shaft bearings, what must be done during the towing operation?
• Gear-driven propulsion systems with a single diesel engine and fixed-pitch propeller • How reduction gear input and output shafts behave when the vessel is being towed and the propeller turns • Why pressurized lubricating oil is critical for reduction gear shaft bearings during rotation
• When the vessel is towed, which shaft (input or output) will tend to rotate due to water flow past the fixed-pitch propeller? • If the main engine is disabled and not running, what happens to the gear-driven lubricating oil pump and the availability of pressurized lube oil? • Which component(s) do you need to keep from turning in order to protect unlubricated bearings, while still avoiding damage to other machinery (like the turning gear or clutch)?
• Verify which shaft(s) actually rotate when the propeller shaft is free and the vessel is moving through the water. • Consider what happens mechanically if you engage the engine turning gear or propulsion clutch while the propeller is being forced to turn by the tow. • Confirm which option best protects bearings that no longer have pressurized lubricating oil, without introducing a new risk of mechanical damage elsewhere.
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