Assessment of Thermal Protection of Life Rafts in Passenger Vessel Abandonment Situations

Abstract

Inflatable life rafts are currently used on almost all passenger, fishing and commercial vessels, and offshore oil installations. Worldwide, life rafts are the primary evacuation system from fishing vessels with relatively small crews to large Roll on/Roll off passenger vessels with over a thousand passengers and crew. While International Maritime Organization (IMO) standards currently require inflatable life raft components to “provide insulation” or “be sufficiently insulated”, there are no performance criteria for these requirements (IMO, 1996). In a passenger ship abandonment situation in cold water, passengers may be wearing very little personal protective clothing. Therefore, life rafts provide the only significant thermal protection against the cold ocean environment while they await rescue. Manufacturers equip life rafts with an insulated floor to reduce heat loss from direct contact with the cold ocean water. The insulation provided is critically important for life raft occupants who have little protective clothing. The heat loss of unprotected persons is drastically increased if there is a layer of water on the floor as would likely be the case when someone climbs into the life raft from the ocean or if water is splashed into the life raft in heavy weather. Experiments were conducted in mild cold (16°C water temperature and 19°C air temperature) and cold conditions (5°C water temperature and 5°C air temperature) to assess the thermal protection of a 16-person, Safety of Life at Sea (SOLAS) approved, commercially available life raft. This paper presents results in the mild cold condition only. It has been found that the wave height effect may be ignored as a first approximation to reduce the number of environmental variables because the results demonstrated that wave height effect is less important with leeway. Heat conductance decreases considerably with floor inflation. Heat conductance is about the same with floor inflated 50% and 100%. The CO2 concentration in the 11-person test exceeded 5000 ppm in less than an hour inside the life raft, with closed canopy and no active ventilation. This hostile microclimate inside the life raft suggests that active ventilation at a known rate is required to keep the CO2 level at a safe controlled level when longer duration tests are to be conducted in the future. Wet clothing has a significant effect on occupant heat loss.