Tensile strength of ropes and friction hitch used in tree climbing work

Abstract

Tree climbing techniques for arboriculture are becoming more and more popular, but like any work activity, there are risks for the operator. The PPE (personal protective equipment) and protective systems studied here include semi-static ropes and friction hitches. The work rope/friction hitch system is a combination that many operators rely on, but unlike current mechanical rope clamps and descenders, they do not have European certifications. For this reason, tensile tests were carried out using a traction bench on rope/knot systems. Two rope models and two types of knots were used to stress the systems and materials as much as possible, so as to observe the resulting ratios. A total of 36 tests were carried out in which measurements were taken, including applied load in traction, knot creep, and rope diameter changes. Several results were obtained, including a maximum load of 18.7 kN, a maximum slip of 9.6 cm and a maximum diameter variation of 3 mm. This work represents a preliminary investigation for verifying the relationship between work ropes and friction knots. Relationships among the variables were observed; differences emerged mainly as a function of the type of knot used rather than the type of rope used. The data obtained is also important for applications towards improving preventative safety measures.