6.7 Considerations In Design Of Harnesses
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Statutory Documents - IMO Publications and Documents - Circulars - Maritime Safety Committee - MSC/Circular.616 – Evaluation of Free-Fall Lifeboat Launch Performance – (22 June 1993) - Annex – Evaluation of Free-Fall Lifeboat Launch Performance - Section 6 – Human Tolerance To Acceleration Forces - 6.7 Considerations In Design Of Harnesses

6.7 Considerations In Design Of Harnesses

  6.7.1 The purpose for having a seat harness in a free-fall lifeboat is to restrain the occupants in the seats during the free fall and subsequent water entry. Serious injury could result if an occupant was to float free of the seat during free fall or was ejected from a seat during water entry. Also, as has been discussed, coupling between the occupant and the seat has an affect upon the potential for injury and the ability to infer that potential.

  6.7.2 Restraint of the occupant must begin with the pelvis. The pelvis can be effectively restrained with a lap belt that has its anchor point situated so that the plane of the loop formed by the buckle is below the iliac crest and the "H" point (the H point is located 8.65 cm above the seat pan and 13.72 cm in front of the seatback). This ideal configuration results in the buckle being located as low on the abdomen as possible. If the belt is located too high on the abdomen, it is possible for the occupant to slide under the belt during an impact (submarining). As such, it is important that the position of the lap belt is not dependent on how the shoulder harness is adjusted. Tightening the shoulder harness should not cause the lap belt to be drawn upward.

  6.7.3 Restraint of the torso is achieved through use of a shoulder harness. The shoulder harness must be configured so that, when properly worn, the occupant does not slide out from behind it. An ideal arrangement is to have straps that pass over the shoulders. The upper anchor of the straps should be above the shoulders and located as close to the center of the seat as possible. The lower anchor should be low on the seat and below the lap. If the shoulder belts are connected to the lap belt, the point of attachment should be to the side of the pelvis so the final position of the lap belt is not dependent upon the adjustment of the shoulder harness.

  6.7.4 A final consideration in the design of a seat restraint system must be ease of use. The seat harness must be easy to don with minimum training, it must be easy to intentionally release, and its configuration must be compatible with the type of lifejacket intended to be used in the lifeboat. Because time is of the essence during an emergency, and because the lifeboat should not be launched until all occupants are seated and restrained, the harness should be designed so that: 1) the proper way to wear the seat harness is fairly obvious, 2) there are not an excessive number of components that must be found, and 3) the buckles and adjustments are easily reached (including those times when all seats are filled). The buckles and anchors must be designed so that they do not release under the inertial loads caused by water impact. At the same time, buckles should be designed so that they can be quickly released if it were necessary to evacuate the lifeboat.

Parent topic: Section 6 – Human Tolerance To Acceleration Forces
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