Determination of criteria for assessing the effect of inorganic acids on synthetic ropes in order to improve the safety of high-altitude works

Introduction. The relevance of this work is due to the frequent occurrences of various chemical substances affecting ropes in sport and in the industry of high-altitude works, as well as due to the lack of open-access information on changes in the rope tensile strength under effect of chemicals.

Aims and purposes. The aim of this work is to improve the safety practices in the usage of ropes both in sport and in industry by assessing the effect of acid solutions on the rope tensile strength, and by providing recommendations for pre-usage visual inspection procedures so that to detect ropes exposed to acids.

Methods. We study the influence of sulfuric acid, hydrochloric acid, and phosphoric acid, as substances widespread in sport and industry, on static polyamide rope, the type of rope used commonly as personal protective equipment. The methods used involve measuring the breaking strength of the ropes after either 30 sec and 1 hr of exposure to different concentrations of these acids. In addition, photographs of ruptures are provided, so that safety specialists be able to detect future causes of rope failures.

Results. The results of the tests conducted show the main markers of the effects of acids on the samples to be the following: increase in the stiffness of the rope in relation to parts not exposed to the acid; increase in the hardness in the areas of exposure, as a result of sintering of individual fibers; sticky surface of the sheath, in the cases when partial dissolution of the sheath takes place.

Conclusion. Though all acid solutions tested have negative impact on rope strength, not all are easy to detect. Particularly deceiving can be ropes with polyether sheath, in which the latter, being less sensitive to acids, may camouflage the damage to inner fibers, while after 30 sec of exposure to 45 % H₂SO₄ such damage leads to decrease in the tensile strength down to 46,8 % of its original strength. Thus, we conclude that the only reliable way to protect oneself from a rope failure is to know the history of the rope in an entire manner.

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