CRANES

Maintenance of Winches and Capstans You will maintain the winch or capstan similarly. Where band brakes are used on the drums, inspect the friction linings regularly and replace them when necessary. Take steps to prevent oil or grease from accumulating on the brake drums. Check the operation of brake-actuating mechanisms, latches, and pawls periodically. Inspect winch drums driven by friction clutches frequently for deterioration in the friction material. Check also to see if oil and grease are preventing proper operation. Lubricate the sliding parts of positive clutches properly. Check the locking device on the shifting gear to see if it will hold under load. CRANES Cranes are designed to meet the following criteria: 1. Hoist, lower, top, and rotate a rated load at the specified speed and against a specified list of the ship. 2. Handle 150 percent of rated load at no specified speed. 3. Withstand a static, suspended load of 200 percent of rated load without dam or distortion to any part of the crane or structure. The types of cranes installed on ships vary according to the equipment handled. The crane equipment generally includes the boom, king post, king post bearings, sheaves, hook and rope, machinery platforms, rotating gear, drums, hoisting, topping and rotating drives, and controls. Some of the components of cranes include booms, king post bearings, sheaves and ropes, machinery platforms, rotating gear and pinions, and drums. Booms A boom, used as a mechanical shipboard appliance, is a structural unit used to lift, transfer, or support heavy weights. A boom is used with other structures or structural members that support it, and various ropes and pulleys, called blocks, which control it. King Post Bearings Bearings on stationary king posts take both vertical load and horizontal strain at the collar, located at the top of the king post. On rotating king posts, bearings take both vertical and horizontal loads at the base and horizontal reactions at a higher deck level. Sheaves and Ropes The hoisting and topping ropes are led from the drums over sheaves to the head of the boom. The sheaves and ropes are designed according to recommendations by NAVSEASYSCOM. This command sets the criteria for selection of sheave diameter, size, and flexibility of the rope. Sufficient fair-lead sheaves are fitted to prevent fouling of the rope. A shock absorber is installed in the line, hoisting block, or sheave at the head of the boom to take care of shock stresses. Machinery Platforms Machinery platforms carry the power equipment and operator’s station. These platforms are mounted on the king post above the deck. Rotating Gear and Pinions Rotation of the crane is accomplished by vertical shafts with pinions engaging a large rotating gear. Drums The drums of the hoisting and topping winches are generally grooved for the proper size wire rope. The hoisting system uses single or multiple part lines as required. The topping system uses a multiple purchase as required. Operation and Maintenance of Cranes The hoisting whips and topping lifts of cranes are usually driven by hydraulic variable-speed gears through gearing of various types. This provides the wide range of speed and delicate control required for load handling. The cranes are usually rotated by an electric motor connected to worm and spur gearing. They may also be rotated by an electric motor and hydraulic variable-speed gear connected to reduction gearing. Some electrohydraulic cranes have automatic slack line take-up equipment. This consists of an electric torque motor geared to the drum. These cranes are used to lift boats, aircraft, or other loads from the water. The torque motor assists the hydraulic motor drive to reel in the cable in case the load is lifted faster by the water than it is being hoisted by the crane. 10-46