Assessment of thermal protection in life rafts in passenger vessel abandonment situations

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\ubaC water temperature and 19\ubaC air temperature) and cold conditions (5\ubaC water temperature and 5\ubaC 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.Peer reviewed: YesNRC publication: Ye

Homogenization of o/w emulsion during the flow through a packed bed of Silicon carbide microparticles

Przedstawiono wyniki badań przepływu rozcieńczonych emulsji olej-woda przez złoże mikrocząstek węglika krzemu (71÷100 µm). Olej mineralny był fazą rozproszoną (5 i 15% obj.), a Tween 40 wykorzystano jako emulgator. Przetłoczone przez złoże emulsje zawierały mniejsze krople oleju i były bardziej jednorodne od emulsji wstępnej. Użyte złoże przede wszystkim spowodowało zanik kropel o średnicy większej od 30 µm. Zaobserwowano również silny wpływ stężenia emulsji na spadek ciśnienia.The results of study on the flow of diluted o/w emulsions through packed beds of Silicon carbide microparticles (71÷100 µm) are reported. The mineral oil as dispersed phase (5 vol% and 15 vol%) and Tween 40 as emulsifier were used. The emulsions pressed through the packed bed contained smaller oil droplets and were more uniform than the preliminary emulsion. The packed bed used in the study caused mainly the disappearance of droplets with diameters greater than 30 µm. A strong effect of emulsion concentration on pressure drop was also observed

Thermal requirements for surviving a mass rescue incident in the arctic - report on environmental conditions

In this project, the objective is to investigate if the current thermal protective equipment and preparedness available to people traveling in the Canadian Arctic are adequate for surviving a major air or cruise ship disaster and to identify the minimum thermal protection criteria for survival. To facilitate experimental design and modeling effort, the environmental conditions along the cross-polar routes for modern aviation and shipping routes for cruise ships in the Canadian Arctic are studied and summarized in this report. There is daily air traffic through the Arctic, so it is important to consider mean and extreme environmental conditions throughout the year as accidents may occur any time. However, cruise ship traffic through the Canadian Arctic is typically between the months of July to late September or early October, where the environmental conditions are less severe. Considering air traffic throughout the year, the daily average air temperature varies between 5\ub0C and -40\ub0C. The extreme minimum air temperature can drop to -55\ub0C and the extreme wind chill can be 70\ub0C. Snow depth can be up to 40 cm during winter months. For cruise traffic during the months of July to September, the daily average air temperature varies between 5\ub0C and 10\ub0C. In July, there is typically one day or less with temperature below \u20132\ub0C. In August, there are typically 5 to 10 days below \u20132\ub0C but not less than 10\ub0C. In September, virtually every day is below 2\ub0C. There are 5 to 10 days below 10\ub0C and approximately 3 days below 20\ub0C. In the summer, typical significant wave height reaches 3 m and peak period varies between 4.5 s and 20 s.Peer reviewed: YesNRC publication: Ye

Thermal Protection in Inflatable Liferafts – Human and Thermal Manikin Testing to Quantify:Training Issues, Assess Occupant Heat Balance and Develop Performance Criteria

Inflatable liferafts are used worldwide as a means of evacuation and survival from almost all ocean‐going vessels, regardless of their size, purpose or region of operation. Vessel size ranges from fishing and other commercial vessels with small crews to offshore oil installations and passenger ships with thousands of persons onboard. While International Maritime Organisation (IMO) standards currently require inflatable liferaft components to “provide insulation” or “be sufficiently insulated”, no performance criteria accompany these requirements. This paper will outline the methodology and results from a three year research project involving a multidisciplinary team which utilised human subjects and a thermally instrumented manikin to investigate the gaps in knowledge for the thermal performance of inflatable liferafts in cold environments. Tests were conducted in a controlled laboratory environment with a 16 person SOLAS‐approved liferaft and air and water temperatures as cold as 5°C. The main variables investigated were clothing wetness (wet and dry) and liferaft floor insulation (insulated and uninsulated). The project’s four main objectives were to: 1) develop thermal protection criteria for inflatable liferafts assuming otherwise unprotected occupants, 2) propose an objective methodology for testing inflatable liferaft thermal protection performance, 3) develop tools for search and rescue planners to predict survival times of liferaft occupants and 4) provide guidance to training authorities and manufacturers. The study found that: 1) the thermal insulation of a combined system of clothing and liferaft using a thermal manikin gave good agreement with measurements using humans, as long as proper corrections for differences between manikin and humans are appropriately applied, 2) system insulation values coupled with a cold exposure survival model can be expected to give search and rescue planners reasonable predictions of survival time in liferafts where hypothermia is the main risk factor and 3) the factors substantially affecting the survival time of liferaft occupants are: whether any type of thermal protective aid (TPA) is worn,clothing wetness, liferaft floor insulation and liferaft ventilation rate

An Overview of Recent Projects to Study Thermal Protection In Liferafts, Lifeboats and Immersion Suits

In a marine evacuation, passengers may find themselves in lifeboats, liferafts or in the water. Survival is more challenging in cold regions and a person’s ability to survive until rescue depends on many factors, including the amount of protection the evacuees have against the cold, as well as the quality of breathing air in liferafts and lifeboats that are enclosed. Currently, international regulations do not provide specific thermal protection and ventilation performance criteria for lifeboats or liferafts. In addition, methods for approval testing of immersion suits have not been standardised and there is resistance in certain jurisdictions to the use of thermal manikins because regulating authorities are unsure of the correspondence between manikins and human. This paper provides an overview of several projects that have been completed and one ongoing by the Maritime and Arctic Survival Scientific and Engineering Research Team (MASSERT) to address the knowledge gaps in these areas. The results contribute relevant knowledge to close these gaps and are being used to advance international standards. They also show the value of using thermal manikins in combination with numerical models to predict the performance of lifesaving appliances when it is impractical or ethically unacceptable to conduct experiments with humans. The tools developed are being applied to create performance criteria and evaluate the performance of Arctic survival gear

Motion response of a full-scale life raft in laboratory tow experiments

A 16-person full-scale life raft was towed in a tow tank in calm water, regular and irregular waves. The objectives were to assess the raft motion response, occupant motion, tow force, effect of tow speed, effects of different test variables (drogue deployment, floor inflation, weight distribution and ballast), and the likelihood of occupant motion sickness. Comparisons of RAOs obtained in regular and irregular waves demonstrated that irregular waves could be used as a cost effective means to determine raft response with a high degree of confidence. They also show that the life raft tow performance is different in waves than in calm water. For example, mean tow force is 20% higher in the sea state tested than in calm water. Floor inflation, drogue deployment, even weight distribution and tow speed increase mean tow force and tow force variation about its mean. The data also show that the same ballast types should be used to access the effects of different variables because manikin and water bag ballast produce different results. Measured occupant heave acceleration was about the same as the raft heave acceleration. From occupant heave acceleration, it was estimated that after 20 hours in the raft, 20% of occupants would vomit. Formulae were proposed to predict tow force in different sea states. Mean tow forces predicted using calm water tow resistance and RAOs derived from regular wave tow tests compared well with measured mean tow force in irregular waves.Peer reviewed: YesNRC publication: Ye

Preliminary evaluation of DND Joint Support Ship design

The report describes the flow visualization, bare hull resistance and free running manoeuvring experiments carried out on a model (IOT 907) of the preliminary design for the Joint Support Ship. The flow visualization experiments were used to design and position the bilge keels. The resistance experiments were used to assess the applicability of the software used to predict the resistance of this design. The manoeuvring experiments were used to assess what could be achieved in terms of turning circle performance.NRC publication: Ye

An empirical method for the estimation of towing resistance of a life raft in various sea states

Current IMO regulations require life rafts to be tow tested only in calm water. In real evacuation situations, life rafts are deployed in the prevailing environmental conditions, with wind and waves. Added wave resistance is small at low wave heights but increases nonlinearly with increased wave height. If life rafts are to be towed in moderate seas (up to 4 m significant wave height), tow force estimates based only on calm water tow resistance become less reliable. Tow patches, towline, towing craft etc. also need to be designed to withstand dynamic wave loading in addition to mean load. Therefore, mean tow force, tow force variation and maximum tow force are important. A full-scale 16-person, commercially available, SOLAS approved life raft was towed in the tank, in upwind, head seas with significant wave height of 0.5 m. The measured tow force showed that it could be treated as a linear system with wave amplitude, by demonstrating that tow force is mainly inertial and follows a Rayleigh distribution. Therefore, extreme-value statistics used for waves can be applied to developing equations for predicting tow force. A method is proposed to predict life raft tow force at different tow speeds and in various sea states, with waves and wind. The method involved using tank experiments to obtain tow force response for one sea state. The information can then be used to predict life raft tow force in wind and waves for different sea states. Three equations are proposed to demonstrate that a simple tank experiment could provide valuable information necessary to empirically estimate the mean tow force, tow force variation and maximum tow force for a specific life raft in different sea states. The equations are developed for upwind, head seas. These equations were extensively validated using tow force measured in the tank. They were partially validated with limited sea trial data, by towing the same 16-person life raft and a 42-person life raft in upwind, head seas with significant wave height of 1.3 m. The equations were able to predict maximum tow forces to within 15% of the measured.Peer reviewed: YesNRC publication: Ye

Description of manouevring trial carried out on CCGA Miss Jacqueline IV \u2013 October 2004

This report describes manoeuvring experiments carried out on the 65 ft. (19.81 m) long fishing vessel CCGA Miss Jacqueline IV off St. John\u2019s, NL October 15, 2004 as part of the Fishing Vessel Safety Project (Proj. 2017). The objective of the project is to acquire quality full-scale motions data on fishing vessels to validate physical model methodology as well as numerical simulation models under development. Eventually, tools will be developed and validated to evaluate the number of Motion Induced Interrupts (MIIs), induced by sudden ship motions, and their impact on crew accidents to develop criteria to reduce MIIs. Although the priority was to collect seakeeping data, a manoeuvring test program was also prepared in the event that calm seas prevailed. Thus an opportunity to acquire manoeuvring data in relatively calm seas was exploited prior to a seakeeping trial carried out on October 17 and 18. This document describes the CCGA Miss Jacqueline IV, the trials instrumentation package, data acquisition system, test program, data analysis procedure and presents the manoeuvring results.Peer reviewed: YesNRC publication: Ye

Experimental study and modelling of thermal protection in liferafts using a thermal manikin and human subjects

Experiments were conducted in cold conditions (5\ub0C water temperature and 5\ub0C air temperature) to assess the thermal protection of a 16-person, SOLAS approved, commercially available liferaft using a thermal manikin and human subjects. The comparison tests included four cases \u2013 1. Inflated raft floor; dry clothing (Idry); 2. Inflated raft floor; wet clothing (Iwet); 3. Uninflated raft floor; dry clothing (Udry); 4. Uninflated raft floor; wet clothing (Uwet). The results demonstrated equivalence in insulation between human subjects and a thermal manikin for all cases of comparison (Idry: Manikin 0.236 (m2\ub0C)/W versus Human 0.224 (m2\ub0C)/W; Iwet: Manikin 0.146 (m2\ub0C)/W versus Human 0.145 (m2\ub0C)/W; Udry: Manikin 0.174 (m2\ub0C)/W versus Human 0.185 (m2\ub0C)/W; Uwet: Manikin 0.101 (m2\ub0C)/W versus Human 0.116 (m2\ub0C)/W). The results also showed the repeatability of the thermal manikin tests (0.177 (m2\ub0C)/W versus 0.171 (m2\ub0C)/W in Udry baseline case; and 0.101 (m2\ub0C)/W versus 0.104 (m2\ub0C)/W in Uwet baseline case). The results indicated that the insulation of a closed cell foam floor is comparable to an inflated floor (0.236 (m2\ub0C)/W compared to 0.221 (m2\ub0C)/W and 0.236 (m2\ub0C)/W for closed foam floor from manufacturer A and B respectively). TPA provided considerable additional insulation than all baseline cases. A test with a human subject wearing a TPA in the Uwet case showed an improvement of 48% over the baseline case. TPA provided more additional insulation than a wet suit in all test cases except Udry case. In Uwet case, the worst test condition, the insulation obtained by sitting on a lifejacket (0.149 (m2\ub0C)/W) is less than wearing a TPA (0.158 (m2\ub0C)/W). Both of these are better than sitting directly on an uninflated floor (0.104 (m2\ub0C)/W) or a closed cell foam floor (0.129 (m2\ub0C)/W). There is a significant decrease in insulation value sitting in 10 cm of water (0.05 (m2\ub0C)/W). Two human subject tests show an insulation value of 0.079 (m2\ub0C)/W and 0.081 (m2\ub0C)/W respectively. A liferaft occupant heat loss model was developed and integrated with Defense R&D Canada\u2019s Cold Exposure Survival Model to predict survival time. For Uwet case, the worst test condition, the survival time is 32 hours and functional time is 24 hours for those experimental conditions.Peer reviewed: NoNRC publication: Ye