On load and Off load release
Off-load mechanism:
The off-load 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.
Ref: Marine Insight Website
