Lifeboat Winch – Gravity Davits

Lifeboat winches used in gravity davits can be powered by electric or pneumatic drives. These drives are equipped with various safety features to ensure the safe operation of the lifeboat.

Electric and Pneumatic Drive Safety Features:

1. Lowering Operation: During the lowering operation, no mechanical assistance is required except for gravity (i.e., the weight of the boat). The only physical work needed is the release of the winch hand brake (dead man’s handle). The hand brake is equipped with a weight attached to the handle. When the operator releases the hand brake, a centrifugal brake provides controlled speed (e.g., 36m/minute) to the lowering process. If the operator loses balance and falls off, the weight in the handle engages the hand brake, causing the lifeboat to remain stationary at the stop position.

2. Hoisting Safety: A ratchet mechanism is incorporated in the hoisting arrangement to prevent the drum from reversing and the boat from falling back into the water in the event of a power failure during lifting. This mechanism provides an additional safety measure.

3. Interlock System: An interlock is provided between the positioning of the manual hoisting lever and the positioning of the power hoisting lever. This ensures that manual hosting and power hoisting cannot be carried out simultaneously, enhancing safety during operations.

4. Power Failure Protection: Both the centrifugal brake and the hand brake remain stationary during the hoisting operation. In the event of a power failure while hoisting the boat, the hand brake will securely hold the boat.

Safety Features for Davits:

1. Positive Turning Out Moment: Davits should have a positive turning out moment throughout the entire travel, even when the vessel is listed at any angle up to and including 25°.

2. Sufficient Strength: Davits should be designed with enough strength to safely lower the lifeboat to the water from the embarkation deck with its full complement of persons on board when the ship has a trim of up to 10° and is listed up to 15° either way.

3. Tricing Pendants: Davits should be fitted with “tricing pendants” to bring the boat alongside the embarkation deck, unless the boat is designed to be boarded and launched directly from the stowed position (e.g., free fall fully enclosed lifeboats).

4. Falls Release: Falls should only be released when the lifeboat is waterborne to ensure safe launch and prevent any premature release during hoisting.

5. Limit Switches: Limit switches should be installed to stop the hoisting motor when the boat has reached the stacking position, preventing any over hoisting or damage to the equipment.

These safety features are essential to ensure the proper functioning and safe operation of lifeboat winches and gravity davits in maritime environments.