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Liferaft design and development: Designed, made and tested to save lives
Like many journeys towards self-improvement, safer liferafts are the cumulative effect of many small steps in the right direction. BETTER SAFE asked Gert Smedmann Rasmussen to explain.
Liferafts today may look different to those first offered by VIKING in 1960, but expertise is needed to identify the many steps taken in the cause of advancing maritime safety and the reasoning behind any given detail.
Lending the experts eye at VIKING is Gert Smedmann Rasmussen – designer, engineer, and maritime safety equipment inventor. A practically-minded man, Gert also sees ensuring that every liferaft is conceived, manufactured and tested for optimized performance as part of his job description.
Stored in compact fiberglass containers on deck, modern liferafts are pressed, folded and rolled in exactly the right way so that they can be inflated almost instantly as survival craft able to accommodate up to 153 persons. Highly durable and with a lifespan of 15-20 years, they stand ready to provide safe evacuation in rough seas and at low temperatures. General performance also requires the liferaft design to deliver on more specific parameters such as water drainage at 2,300 liters a minute to keep those on board dry.
Remarkable for the uninitiated, such attributes are actually the necessary requirements for a liferaft doing its job under the Convention for Safety of Life at Sea (SOLAS).
“Chapter III of SOLAS gives details for the types and number of liferafts to be carried as per the size and type of the ship, but the work we do in designing, manufacturing and testing equipment can increase the chances of survival at sea,” he says. “That is not a job that you can ever say is ever truly finished.”
However, SOLAS represents a minimum standard for global maritime safety, and it evolves as new evidence is considered and can also be superseded by regional regulations. This means that the forward-looking work Gert and his design colleagues engage in needs to consider both how to optimize liferaft performance against the existing standard and anticipate the safety requirements ahead.
Rules and realities
An example of optimization is the ‘boarding ramp’ VIKING has phased in to allow people in the water to get into the liferaft. Where the previous solution relied on upper body strength and the ability of evacuees to drag themselves aboard, the new ramp features a strengthened loop which trails over the side to allow the boarder to step on and haul themselves up using leg muscles.
Developments required to match a changed regulatory agenda include the development of liferafts capable of performing at - 52 degrees Celsius, in line with the IMO’s Polar Code and in expectation that the Northern Sea Route through Russian arctic waters will become a key waterway for commercial ships.
The practical approach
With regulations and industry requirements set to evolve on a continuous basis, Gert remains convinced that meeting the challenges ahead will rely on taking the practical approach which has served VIKING so well over the last 60 years. CADCAM tools are clearly very useful, he acknowledges, but where liferafts are concerned - even today - the starting point for new and improved liferaft design lies in 2D drawing before 3D visualizing and small-scale prototyping.
"Believe me, the elasticity of the materials used for liferafts limits the usefulness of computer modelling in 3D. Rubber – even the synthetic kind - flexes and stretches differently in different directions, while the best way of testing how glues respond is by physical modelling."
Gert Smedmann Rasmussen
Designer, engineer and maritime safety equipment inventor
In fact, the practical test is a feature at all stages of the liferaft design, production, verification and delivery process, Gert emphasizes. A tensile testing machine is used to test the strength of all materials, for example, which stretches them at high pressure to find their breaking points.
Again, during production, samples are taken of the water-resistant adhesive in use for analysis after one day and seven days to verify their resilience, while sewing work on the canvas canopies is checked frequently and random samples from each batch of liferafts will be inflated to double their required working pressure for test purposes.
Even then, however, the internal testing process is not over, says Gert. Also critical is the role played by the company’s Development Test and Verification (DTV) department. The 14-strong DTV team base their work at facilities at the port of Esbjerg, with a test of a VIKING Life-Saving Equipment system underway or under preparation at any given time. In addition, the DTV team takes responsibility testing systems in harsh weather conditions, making regular sea trials an essential part of verifying liferaft performance.
Safety variables
Maritime safety is subject to other variables than weather which can affect its regulation and, in turn, life-saving equipment design. Gert observes that inclusion, for example, is increasingly becoming a topic for discussion. “Overall, VIKING’s R&D has been focusing on the effectiveness of evacuation procedures for wheelchair users, for example, and this is an area we can also foresee benefiting from regulatory oversight.”
Again, current regulations work on the basis that the average weight of the liferaft passenger is 82.5kg. Clearly, this is an average figure designed to accommodate a range of regions of origin, as well as different age groups and genders.
“We know that this is something that will affect us at some point and, perhaps we will have to go significantly higher in the years ahead,” he says. “Ultimately, we may need to have more freeboard to accommodate regulation on this point, or consider how larger individuals change seating arrangements, or think about reducing capacity.
“However, for the offshore market, we have already developed approved liferafts with lower capacity for people weighing above the 82.5 kg.” When it comes to measuring our own performance perhaps the most interesting thing is that the test reports showed what knew before - that our liferafts could withstand the challenge without any problems.”
