Did you know that many of the fall arrest devices designed for vertical work are unable to stop a fall when the rope on which they act is in tension? This is what emerged from a survey conducted in late 2012 by BARA, the Danish Association of vertical works, testing five known models.
The use of sliding in vertical fall arrest devices work is mandatory in Europe since 2001, when Directive 2001/45 / EC was adopted.
The Royal Decree specifies that the safety rope "will be equipped with a mobile fall prevention system which follows the movements of the worker." The best way to ensure that we meet this legal requirement is to use control devices for vertical rope work under EN 12841 A standard.
Now if these devices are perfectly safe in normal uses, there are situations where they are unable to stop a fall: when they are used on a tensioned line. These situations are rare but can occur, for example, the need for a rescuer using the same rope as the casualty.
Such maneuvers are an important part of the educational content related to rescues at height imparted by the main international professional associations in vertical work, hence the need for additional security measures.
The fact that devices with EN 12841 A display ineffective in situations that may occur in vertical works evidence that the test methods in this standard does not provide for this possibility. I will not be advisable to use devices outside of UNE-EN, quite the contrary but this shows that technical standards should never be considered as the highest level of security, but rather, as the minimum required level.
Examples are functions with which some manufacturers equip their devices, functions not required by the technical rule but which increase the level of security: Coding shells in panic functions and descenders, cam wear indicators and critical components, etc.
Aware of this problem, the Danish Association of vertical works, BARA, set out to do a number of tests whose results, to put it bluntly, make your hair stand on end: five models of fall arrest devices tested, only one is able to stop a fall on a tensioned line.
Tests
The study tested the following devices:- Kong Back-up
- Troll / Yates / ISC Rocker
- ISC RED
- Petzl ASAP
- Petzl Shunt
Although the shunt is no longer a valid fall arrester for vertical jobs since Petzl issued a circular to this effect in 2012, it was decided to try it out of curiosity having been used for years throughout the world, mainly by companies and technical IRATA.
Test conditions
He used a rope of 11.2 mm of the Sterling brand. This rope was burdened with a mass of 100 kg (the "victim") to 30 cm of soil.He used a dummy 80 kg (the rescuer) that was dropped on the fall line in tension (rope work "victim").
-also was tested with a mass of 50 kg, to check if the variation in mass alter results.
-The Rocker and Kong Backup devices were connected directly without using rope lanyard (provided by the manufacturer).
He used a lanyard 60 cm made of dynamic rope for Shunt and Red (according to manufacturer in the case of the Internet, not the shunt).
He used a L57 again for each ASAP test (mandatory requirement by the manufacturer) .
-The Fall devices were connected to the sternal ring harness.
-the Mass that was dropped was placed as high as possible above the device to simulate situations factor 2 on.
Results
Troll / Yates / ISC RockerThe Rocker failed both tests with both 50kg and with 80kg. The author of the test discourages its use in situations tightrope.
This device failed the test with 50 kg and stopped the fall in the 80 kg test. The author of the test discourages its use in situations tightrope.
This device failed both tests and 80 -50 kg. The author of the test discourages its use in situations tightrope.
The Asap he stopped falling in both configurations of 50 and 80 kg. The author considers it acceptable in a situation of tight rope.
This device passed the test in both configurations but in a later test in two attempts failed ... The author of the test discourages its use in situations tightrope.
Of the 5 devices tested only the ASAP is able to stop a fall on a tensioned line situation. However the test author reminded us that this device has other troubling weaknesses such as for example the high height of fall required by the manufacturer (5 meters + 10% chord length for a load of 2 persons), which for example would use his unworkable in many training centers that do not exceed 5 or 6 meters.
Of course, all these devices work well as the test methods specified in the standards for which have been certified - EN 12841 A, 353.2 or both in the case of some appliances-. However, these test methods do not allow for tensioned line situation simulated in the test conducted by BARA, which corroborates what we said at the beginning that the technical standards do not involve the highest level of safety applicable to a product, but on the contrary, the lowest level required.
The question to be asked in light of these results is, should they upgrade the standard for vertical sliding fall arrest device for work and adapt to the reality of the sector or, conversely, should be used in vertical procedures which should be adapted to the standard?
