Residual strength of carabiners used by tree climbers

Abstract

Tree climbers increasingly use carabiners and apply them in situations for which they are not designed. Because failure of carabiners can result in serious injury or death, the following study tested how well carabiners endure the stress to which climbers subject them. This study distributed carabiners of four types (all manufactured by Petzl) to climbers in Massachusetts and New York, USA, and collected them a year later. Then, carabiners were broken in a universal testing machine and measured the maximum load, as well as surface roughness. No carabiners broke below their rated strength; and used carabiners were, with one exception, as strong as new carabiners. Surface roughness was a weak, but significant, predictor of strength. Findings are discussed in light of climber safety and the importance of conducting long-term studies. © 2009 international society of arboriculture.