Boat winches are intended to handle rescue boats carried by sea-going and river ships. These do not include the winches used to regularly hoist and lower boats and launches in the performance of routine work and finishing operations of the ship.
Under the International Convention for Safety of Life at Sea all ships must be equipped with rescue boats. The same Convention specifies a number of requirements to davit on which the operating conditions of the electric drive depend to some extent.
The boat-handling gear must provide the means for:
The suspenders can be lowered either by unwinding the cable from the drum manually or by means of an electric drive.
The principle mode of operation of a boat winch drive consists of lifting the lifeboat, once at a time, a limited time period not longer than 5 min. The boat lifting speed is 0.1 to 0.15 m/s. The choice of the motor must be made so as to ensure starting of the motor at the maximum design load. As the boat lifting time must not exceed 5 min the motors may have to sustain heavy overloads as compared with the catalogue data which represent 60 min ratings.
The control systems for the motors of the boat winches are quite simple. Starting and stopping of a-c motors are effected by means of magnetic starters with a local push button control which may be reversible or non-reversible, depending on the construction of the winches.
The boat-handling gear must provide the means for:
- swinging-out of boat booms or davit with a fully fitted-out boat and lowering of the boat with the full number of people and with the ship rolling by 15° port or starboard;
- lifting of a fully fitted-out boat with the full number of people at a list of up to 8° at such an antirol at which the boat moves clear of the ship, and the swinging in of the davit with a fully fitted-out boat and a minimum number of people;
- swinging-out of booms or davits without a boat with the ship stopped even-keel.
The suspenders can be lowered either by unwinding the cable from the drum manually or by means of an electric drive.
The principle mode of operation of a boat winch drive consists of lifting the lifeboat, once at a time, a limited time period not longer than 5 min. The boat lifting speed is 0.1 to 0.15 m/s. The choice of the motor must be made so as to ensure starting of the motor at the maximum design load. As the boat lifting time must not exceed 5 min the motors may have to sustain heavy overloads as compared with the catalogue data which represent 60 min ratings.
The control systems for the motors of the boat winches are quite simple. Starting and stopping of a-c motors are effected by means of magnetic starters with a local push button control which may be reversible or non-reversible, depending on the construction of the winches.
