Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGprecautions should be taken to lock the mainshaft.11. Where the rotation of the propellers mayresult in injury to a diver over the side, or indamage to the equipment, propeller shafts shouldbe locked.12. When a ship is being towed, the propellersshould be locked, unless it is permissible andadvantageous to allow the shafts to trail with themovement of the ship.13. When a shaft is allowed to turn or trail,the lubrication system must be in operation. Inaddition, a careful watch should be kept on thetemperature within the low pressure turbinecasing to see that windage temperatures cannotbe built up to a dangerous degree. This can becontrolled either by the speed of the ship or bymaintaining vacuum in the main condenser.14. The main propeller shaft must be broughtto a complete stop before the clutch of the turninggear is engaged. (If the shaft is turning,considerable damage to the turning gear willresult.)15. When the turning gear is engaged, thebrake must be set quickly and securely to pre-shaft turning and damaging the turningvent thegear.BALANCEDSEMIBALANCEDRUDDER STOCKPLATFORM DECKSHELL PLATINGUNBALANCEDFigure 5-24.— Rudder assembly.147.523.99 Figure 5-25.— Balanced, semibalanced, andunbalanced rudders.110