Liferafts: SOLAS tested to the limits

The testing regime behind liferaft compliance provides a strong example of the reasoning regulators apply when they make rules to deal with real life emergency situations.

Compliance with global maritime safety regulations is not optional but the reasoning behind a given set of rules can often be opaque, with the user sometimes finding fault with individual requirements or tempted to see a dislocation between dry legal language and real-life situations.

But the legalese is a manifestation of the precision regulators bring to their craft and reflects repeated consideration of the same issues, lessons learned from actual maritime incidents and investigations, and consensus among a broad range of expert stakeholders.

Among those stakeholders, it is not surprising that the flag administrations responsible for agreeing global maritime regulations at the International Maritime Organization and the technical bodies advising them routinely to consult with life-saving appliance developers themselves, including VIKING. After all, suppliers - in combination with the recognized organizations authorized by flag states - play a full role in testing that the LSA in use meets the detailed requirements of IMO instruments.

One comprehensive account of the reasoning behind the maritime safety rules and their development can be secured by considering the tests used to ensure liferafts and the shipowners responsible for deploying them uphold compliance during emergency situations.

Faced with the need to abandon ship, and having assembled evacuees at their muster stations for example, the crew will be required to throw or lower liferafts overboard. Understandably, in doing so the user would expect to be assured that the equipment will be up to handling the resulting impact of hitting the water or the stresses and strains of davit-handling.

Hitting the water

Under the Life-Saving Appliances Code (LSA Code), throw overboard liferafts need to have been verified as being constructed to operate satisfactorily when dropped into the water. In this case, liferafts are stored in fiberglass containers which hold high-pressure gas used for inflating life rafts at the time of emergency.

Historically, the drop height was envisaged as 18m but liferafts today are routinely stowed at far greater heights above the waterline: in each case, they need to be satisfactorily drop-tested from at least that height.

Given that a container falling from heights of 60m and upwards can reach quite a speed by the time it hits the water, additional steps have taken to protect the equipment, including greater use of foam to line the container and safeguard the emergency kit against impact. Every passenger ship davit-launched liferaft, meanwhile, must be capable of being boarded by its full complement of persons, while cargo ship davit-launched liferafts will need to be boardable by the full complement within three minutes of the instruction being given.

Abandoning ship

With the emergency evacuation procedure underway, there is no time to lose but there is also no room for compromise on safety. In the case of the davit-launched liferaft, for example, lowering at sea in unpredictable conditions in mind, davit-launched liferafts must also be capable of withstanding a lateral impact against the ship’s side at a velocity of 3.5 m/s and a drop into the water from a 3 m height without compromising its ability to function.

At VIKING, the testing process also involves lifting a weight of four times the weight of a full vessel where average weights of those on board are the SOLAS average of 82.5kgs per person.

Where throw-overboard liferafts are concerned, inflation takes place at water level in no more than one minute in a real life situation, which is why the rules demand a test process able to emulate conditions experienced in temperature ranging from -30°C to +65°C.

Hard landings

Whatever the liferaft’s capacity and whether the evacuee is jumping into it or joining via a connecting chute, the platform must also be robust enough to handle repeated landings. For this reason, liferafts are subjected to jump tests which simulate the impact of a person weighing 82.5kgs. The liferaft needs to be capable of withstanding repeated jumps onto it from a height of at least 4.5 m above its floor both with and without the canopy erected.

The liferaft also needs to be fitted with an efficient painter line of not less than 10 m in length plus the distance from the stowed position to the waterline - or 15 m, whichever is the greater. Its purpose is to provide a connection between the ship and the life raft to pull the liferaft from its container, but one which can be broken to ensure that the life raft is not dragged under by the sinking ship (breaking at 2.2 ± 0.4 kN).

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In a real-life emergency, liferafts will also be taking boarders from the water, and this eventuality is subject to a separate boarding and closing arrangement test. Again, whether a liferaft is designed to carry 6 and 150 persons, the expectation is that it will maintain a positive freeboard when full: compliance here is subject to a loading and seating test.

Understandably, given the fact that most onboard will be first-time liferaft passengers, will be of differing sizes and will have boarded in a hurry, there is every likelihood that weight onboard will be unevenly distributed. For this reason, liferafts are also subject to a stability test.

Rescue underway

Having safely negotiated the evacuation and settled themselves inside the liferaft, passengers will be aware that their ordeal is far from over and, perhaps, not be in the mood to appreciate the testing that has been done to verify that their inflatable craft can withstand the high winds and hard weather.

Like regulations, for example, the resilience of fabrics and glues develop over time. In fact, by law, the liferaft must have a canopy to protect the occupants from exposure which is automatically set in place when the life raft is launched and waterborne. The canopy consists of two layers of material separated by an air gap, which needs to show itself as being able to withstand being hit by 2,300 liters of water per minute over a 5 minute period without letting more than four liters to enter the liferaft.

Having survived the elements while waiting for rescue, liferafts must also be able to handle the rescue itself, and be buoyant and stable enough to withstand boarding by rescue personnel or robust enough to handle towing should that be the preferred option. For example, the life raft and its fittings must be sufficiently robust as to allow towing at a speed of 3 knots in calm water when loaded with its full complement of persons and equipment and with one of its sea anchors streamed.

In fact, technically, and as the contents of regulation emergency kits affirm, every liferaft needs to be constructed as capable of withstanding exposure for 30 days afloat in all sea conditions. However, no passenger is likely to want to verify this capability in person, which is another reason why testing for compliance must be rigorous in all respects.

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