| Abstract | Lifeboats are used as a means of evacuation from offshore structures and marine vehicles. Currently, the International Maritime Organization (IMO) Lifesaving Appliances (LSA) Code does not specify thermal protection and ventilation criteria for lifeboats. The objective of the present study was to assess the thermal protection and ventilation rate of lifeboats for the Arctic environment. Two SOLAS approved lifeboats were used for model development: a 72-person lifeboat with engine off and a 20- person lifeboat with engine on. The dilution experiments (where the rate of reduction of concentration in injected carbon dioxide was estimated, to determine ventilation rate) with the 72-person lifeboat found that the lifeboat had a ventilation rate of 2 l/s with vents open, which is inadequate to maintain carbon dioxide level below 5000 ppm. The 20-person lifeboat had 11.6 l/s at full engine power and 7.8 l/s at half power; both being inadequate ventilation rates. A thermal manikin and a mathematical model were used to assess heat and cold stress of lifeboat occupants under various lifeboat, occupancy and ventilation conditions in the Arctic summer environment. In a lifeboat with the engine running, the occupants are likely to suffer heat stress unless a ventilation rate of several hundred litres per second can be achieved. The effect of occupant heat loss with ventilation was also assessed in the 72-person lifeboat with the engine off. When the lifeboat is carrying half the number of people for which it is rated and when these occupants are wearing dry reference clothing and lifejacket, the ventilation rate could be increased to 100 litres per second (minimum ventilation to keep carbon dioxide below 5000 ppm is 27 l/s) to achieve thermoneutral heat loss (51.7 W/m2). When the lifeboat is fully loaded, the ventilation rate can be increased to 300 l/s to achieve a similar microclimate (minimum ventilation rate to keep carbon dioxide level below 5000 ppm is 54 l/s). A higher ventilation rate is required if the engine is on. This suggests that an increase in ventilation rate needs to be implemented to avoid heat stress and provide adequate ventilation. In conclusion, the use of a thermal manikin supported by a simple heat loss model helped define the adequate ventilation rates in lifeboats under simulated Arctic summer conditions and showed that the current risks are mainly carbon dioxide toxicity and heat stress. |
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