Wpływ węzłów na parametry mechaniczne lin stosowanych w sprzęcie chroniącym przed upadkiem z wysokości
Impact of knots on mechanical parameters of ropes used in fall arrest equipment

Summary/Abstract: Textile elements, including mainly ropes and webbings of different designs, made of various raw materials, are used in personal equipment protecting against falls from a height. The examples of such equipment are horizontal and vertical anchor lines, self-locking devices on a flexible anchor lines, textile energy absorbers, lanyards, etc. Particular attention should be paid to the components of such equipment containing fibre ropes of up to several dozen meters length, due to their impact on the course of the fall arrest. In the case of equipment used in sports and recreation, but also in industrial conditions, e.g. in arboristics, the use of ropes is often associated with the formation of knots. Due to the impact of such structures on human safety, a study of the mechanical parameters of fibre ropes with knots of different types was undertaken in CIOP-PIB in 2020. The paper presents tests of fibre ropes of different design in terms of knotability ratio. Parameter K, as determined in these tests, refers to the certainty of tying a knot on a fibre rope, i.e. the impossibility of its self-loosening. Dynamic studies of the performance of fibre ropes ending in loops with three types of knots are presented. The results showed that rope endings in the form of a loop with a knot absorb significantly more kinetic energy than a straight section of a fibre rope when arresting a fall from a height. Studies of the effect of knots on the breaking force of fibre ropes were also presented. The results indicate that the breaking force in the case of a loop with a knot can be e.g. 50% lower than that characterizing the straight section of the rope on which it was formed.

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