{"id":754,"date":"2025-12-31T21:16:50","date_gmt":"2025-12-31T21:16:50","guid":{"rendered":"https:\/\/swarm.craa.cz\/?p=754"},"modified":"2026-03-01T15:00:18","modified_gmt":"2026-03-01T15:00:18","slug":"poskozeni-oka-horolezeckeho-motylka-a-jeho-vliv-na-bezpecnost-lezce-poznatky-z-testu","status":"publish","type":"post","link":"https:\/\/swarm.craa.cz\/en\/poskozeni-oka-horolezeckeho-motylka-a-jeho-vliv-na-bezpecnost-lezce-poznatky-z-testu\/","title":{"rendered":"Po\u0161kozen\u00ed oka horolezeck\u00e9ho mot\u00fdlka a jeho vliv na bezpe\u010dnost lezce: poznatky z test\u016f"},"content":{"rendered":"
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Year 2, Issue 3, 2025
swarm.craa.cz, ISSN 3029-7508
Safety, Work And Rescue Magazine
Pages 12-23, https:\/\/doi.org\/10.71319\/swarm2503.12-12<\/p>\n<\/div>\n\n\n\n

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\"Strength<\/a><\/figure><\/div>\n\n\n<\/div>\n<\/div>\n\n\n\n

Alpine Butterfly Loop Damage and Its Impact on Rope Access Technician Safety: Insights from Testing<\/strong><\/h1>\n\n\n\n\n\n

Ond\u0159ej Belica<\/strong>1<\/sup> <\/strong>\"\"<\/a><\/sup><\/p>\n\n\n\n

1<\/sup> CRAA \u2013 Institute of Occupational Safety at Heights; obelica\"SWARMlezectvi.cz<\/p>\n\n\n\n\n\n

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Type of Paper
<\/strong>Review Article

Keywords<\/strong>
Alpine butterfly knot, fall protection, knot strength test, rope access, rope damage.<\/em><\/p>\n\n\n\n\n\n

CC BY licensed Open Access article<\/em>
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Abstract<\/strong>
This review systematically analyzes the results of tests conducted in 2021 on damaged alpine butterfly loops to assess whether such loops can safely used to secure a rope access technician while passing the knot. Findings indicate that tying the knot itself reduces rope strength more significantly than operational damage. Damage at the apex of the loop has the greatest impact, yet even damaged loops frequently meet or exceed the minimum requirements specified for certain personal protective equipment.<\/em><\/em><\/p>\n\n\n<\/div>\n<\/div>\n\n\n\n

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Introduction<\/strong><\/h2>\n\n\n\n

If personal protective equipment (PPE) against falls shows any signs of damage, whether minor or major, it must be removed from service. In practice, however, this rule is not always followed in the case of ropes. It is common, instead, to tie an eccentric knot at the damaged section to isolate it (most often an alpine butterfly) and continue using the rope for the remainder of the workday. Only at the end of the day (or, in some cases, at the end of the entire task or expedition) is the damaged section of the rope cut out, and the shortened rope is then used.<\/p>\n\n\n\n

For many users, the loop isolating the damaged section of the rope remains unusable, and some training systems therefore do not allow a rope access technician to clip a personal lanyard (cowstail) to the loop when passing the knot [1, p. 15]. The question arises whether such caution is necessary, since the rope is doubled within the loop, meaning that the damage may not affect the overall strength of the knot. This question was precisely the motivation for a study conducted in the summer of 2021. The aim of the study was to determine whether damage to the loop affects the overall strength of the knot and whether a loop with such damage is sufficiently strong to secure a rope technician [2].<\/p>\n\n\n\n

\"Clipping<\/a>
Figure 1: Clipping to the loop when passing the knot<\/strong> [2, p. 1]<\/sup><\/figcaption><\/figure><\/div>\n\n\n\n

1 Materials<\/strong><\/h2>\n\n\n\n

The tests were conducted on a vertical hydraulic testing machine (hereinafter referred to as the testing rig) with a maximum force capacity of 200 kN and a measurement accuracy of 0.5% [2, p. 3]. The tearing speed was manually controlled so that the displacement rate of the pulling mechanism did not exceed the standard-specified limit of 50 mm\/min [3, Art. 4.1.2.2].<\/p>\n\n\n\n

1.1 Rope<\/strong><\/h3>\n\n\n\n

For the tests, new, previously unused, low-stretch ropes with a diameter of 10.5 mm1<\/a><\/sup>, type A, manufactured in January2<\/a><\/sup> and June3<\/a><\/sup> 2021, and certified according to EN 1891, were used. These were white polyamide Truck ropes produced by Courant. According to the manufacturer, the static strength of the rope was 30 kN, the knot strength (using a figure-eight loop) was 19 kN, and the sheath contributes 47 % of the total rope strength [2, p. 2].<\/p>\n\n\n\n

1.2 Test specimens<\/strong><\/h3>\n\n\n\n

The knot chosen for the study was the alpine butterfly [5, Art. 6.1.2]. The research examined not only the effect of rope damage itself but also the influence of damage location on the strength of the butterfly loop. All test specimens were cut with a hot knife4<\/a><\/sup>:<\/p>\n\n\n\n