Taking safety to the edge
July 1st 2008

Most standard fall arrest lanyards provide excellent protection when the lanyard hangs free during and after a fall. They are, however, much less satisfactory if the lanyard passes over a sharp edge. John Goacher of Sperian Protection explains

For anyone whose job involves working at height, the Work at Height Regulations make the provision of appropriate personal protective equipment (PPE) mandatory. In many cases, this will take the form of a full body harness and a fall arrest lanyard.

Until now, however, these lanyards have only been tested by methods that simulate a vertical fall, with the lanyard hanging free of obstructions.

Unfortunately, the situation in the real world is often rather different. Consider, for example, a person working on a flat roof who is using a lanyard. If the worker falls over the edge of the roof the lanyard will experience an impact at the roof edge and may be cut, allowing him or her to fall to the ground.

Similar situations may also occur in steel erection, working with scaffolding, working on electricity pylons and in many other circumstances.

New testing methods In Germany in particular, a lot of work has been done to address this issue of lanyards and sharp edges. The result is a new testing methodology for lanyards, which is expected to be added to the existing EN354 standard in the future.

Naturally, the lanyard itself has to be manufactured from material that is resistant to cutting by the sharp edge and work carried out by Sperian has found that a specifically plaited rope construction using the latest polymer fibres is the best way of achieving the performance required.

Simulates a fall The test procedure for these lanyards is extremely rigorous and reproduces a factor 2 fall over a sharp edge. Factor 2 is the worst case fall situation and simulates a fall where the person is connected to an anchorage point below foot level. For this test, the lanyard is attached to an anchor point and then runs above the horizontal surface that has a sharp edge.

For the purposes of the test, the 'sharp edge' is defined as an edge with a radius of 0.5mm ±0.1mm. To the free end of the lanyard, a mass of 100kg is attached and, during the test, this falls vertically from a height of 2m above the sharp edge (see diagram). The test system includes a load indicator, and this must show that the load is never subject to a force in excess of 6kN during this dynamic phase of the test.

After the system has come to rest, a further static load of 200kg (350kg for webbing) is added to the load end of the lanyard. To meet the requirements of the proposed new standard, the lanyard must then remain intact for a minimum of 3min.

The test is first carried out with the point of contact of the lanyard and the sharp edge in line with the anchor point. It is then repeated with the point of contact displaced by 1.5m, so that, after the test mass has fallen, the lanyard slides along the sharp edge and is, therefore, more likely to be cut. Once again, the additional load is added and the lanyard must support this for at least 3min.

It's not hard to see that the situations modelled by the sharp edge testing procedures are very much closer to those that are likely to be encountered in real world situations. It's also true that many existing lanyards fail these tests dramatically, typically parting almost instantly at the point of contact with the sharp edge.

Even though they might comply with existing standards, these products clearly do not provide workers with the level of protection they have a right to expect. It is, therefore, logical to seek out products, such as those in the Miller by Sperian range, which have been shown to pass the sharp edge tests.

Safety is everyone's concern, and the new sharp edge tested lanyards play a major role in enhancing safety for those who work at height.

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