Safety
Life rafts correct installation If the hydrostatic release unit (HRU) securing your life raft is not installed correctly, it will not activate properly. Your life raft may be your means of survival if your vessel sinks—make sure it is installed correctly. By Sarah Cameron
AMSA accredited surveyors and marine inspectors continue to find life raft HRUs incorrectly installed. Whatever mounting system your life raft uses, there are a few things you need to know. HRUs are purchased separately to your life raft. When installing the new HRU, follow the instructions provided with the HRU and the life raft. As part of your planned maintenance schedule, visually check that the HRU is in date and in sound condition at least every 12 months, or as recommended by manufacturer’s instructions. Most HRUs have an expiry date, and must be periodically replaced (usually every two years). There are also serviceable types, which must be serviced and recertified by an approved service agent. During crew training explain the HRU’s operation and how to carry out a controlled abandon-ship procedure. Document these procedures in your safety management system and put them into practice through regular drills. 29
Working Boats May 2020
Float-free and automatic inflation
Manual release
Life raft canisters are buoyant and designed to float. If the canister submerges, the HRU enables the life raft’s securing mechanism to break free. When the life raft submerges to a depth of about four metres, the water pressure acts on the HRU’s diaphragm, releasing a spring-loaded knife or chisel to cut through the rope and release the life raft. If there are no obstacles the life raft canister will float free to the surface (similar to the mechanism in float-free EPIRBs).
Manual release occurs where passengers and crew are required to abandon the vessel in a more controlled manner.
The life raft canister floats to the surface, pulling out the painter, which remains connected by a weak link to the vessel.
For this system to work, the painter must be fastened to a strong point and the person manually inflating the raft must have a knife to cut the painter to release the life raft from the vessel once everyone is on board.
When the painter is pulled to the end, the gas cylinder in the life raft is activated and inflates the life raft. At this point, the buoyancy of the inflated life raft is enough to break the weak link connecting the painter line to the vessel, allowing the life raft to float to the surface, fully inflated and ready for boarding.
The strap securing the life raft must be capable of being released quickly and easily—for example, by a senhouse slip or pelican hook. Someone must then physically throw the life raft over the side and pull the painter line to inflate the life raft.
