There are different types of lifeboats used on board a ship on the basis of the type of ship and other special requirements. Not all the lifeboats have the same type of releasing mechanisms, for the launching of a lifeboat depends on several other factors. In this article, we will take a look at the main types of lifeboat releasing mechanisms and also learn about the SOLAS requirements for lifeboats.
Types of lifeboat releases: On load and offload release.
There are two types of lifeboat releasing mechanisms- on load and offload. These mechanisms release the boat from the davit, which is attached to a wire or fall by means of a hook. By releasing the hook the lifeboat can be set free to propel away from the ship.
The offload mechanism releases the boat after the load of the boat is transferred to water or the boat has been lowered fully into the sea. There is a hydrostatic piston unit provided at the bottom. the piston is connected to the operating lever via a link. As the ship becomes waterborne, the water pressure will move the hydrostatic piston up. The piston will continue to move up, pushing the lever and as a result, it will operate the hook arrangement releasing the fall wire. There is a safety pin arrangement provided near the clutch box, which disables the offload release (in case of rough weather or hydrostatic piston malfunction) allowing the operator to perform onload release of the lifeboat.
On load mechanism:
On load mechanism can release the lifeboat from the wire, with the ship above the water level and with all the crew members inside the boat. The load will be still in the fall as the boat would not have touched the water. Normally the on-load release is operated when the boat is about to touch the surface of the water so that the fall is smooth without damaging the boat and harming the crew inside. A lever is provided inside the boat to operate this mechanism. As the lever is operated from inside, it is safe to free the boat without going out of the lifeboat, when there is a fire on the ship.
Free Fall lifeboat release:
In Free fall lifeboat, the launching mechanism is similar to on load release. the only difference is that the freefall lifeboat is not lowered till 1m above water level, it is launched from the stowed position by operating a lever located inside the boat which releases the boat from rest of the davit and boat slides through the tilted ramp into the water.
SOLAS and LSA code Requirements for lifeboat:
-The size, number and the capacity of the lifeboat for a merchant vessel is decided by the type of the ship and number of ship’s crew, but it should not be less than 7.3 m in length and minimum two lifeboats are provided on both side of the ship (port and starboard).
-The requirement for the lifeboat of a cargo ship with 20,000 GT is that the boat must be capable of launching when the ship is heading with a speed of 5 knots.
-The lifeboat must carry all the equipment described under SOLAS which can be used for survival at sea. It includes rations, fresh water, first aid, compass, distress signaling equipment like rocket etc.
-The ship must carry one rescue boat for rescue purpose along with other lifeboats. One lifeboat can be designated as a rescue boat if more then one lifeboat is present onboard ship.
-The gravity davits must be held and slide down the lifeboat even when the ship is heeled to an angle of 15 degrees on either side. Ropes are used to hold the lifeboat in the stowed position with the cradle. These ropes are called gripes.
-The wires which lift or lower the lifeboat are known as falls and the speed of the lifeboat descent should not be more than 36m/ min which is controlled by means of centrifugal brakes.
-The hoisting time for the boat launching appliance should not be less than 0.3 m/sec with the boat loaded to its full capacity.
-The Lifeboat must be painted in international bright orange color with the ship’s call sign printed on it.
-The lifeboat station must be easily accessible for all the crew members in all circumstances. Safety awareness posters and launching procedures must be posted at lifeboat station.
-Regular drills must be carried out to ensure that the ship’s crew members are capable of launching the boat with minimal time during a real emergency.