At the sharp edge of safety

Fall arrest systems are required when there is any risk that a worker may fall from an elevated position. The system activates only when the actual fall occurs and typically consists of a full-body harness with a shock-absorbing lanyard or retractable lifeline, an anchor point and a means rescue. To specify a fall arrest system, it is important that the specific risks of the application involved are considered.

The Work at Height (WAH) Regulations, introduced a decade ago, state: 'A fall arrest system shall not be used in a manner which involves the risk of a line being cut' (Schedule 5, part 3). Performance of a lifeline will vary dependant on the construction of the line and the nature of the edge. So, for example, on comparable diameters of lifelines, a stainless steel lifeline will be weaker when used over edges than a galvanised steel line and steel edges tend to cause more damage than concrete.

Risks are compounded by the fact that sharp edges are found in many leading edge applications. A typical example of a leading edge application would be the installation of sheet roofing materials where the installer’s fall protection system is anchored at foot level behind him. As the installer moves out and away from the anchor point, there is the risk of a fall over the edge of the building or the edge of an elevated platform.  

While the primary risk in leading and sharp edge applications is where the lifeline passes over a sharp edge – it can be frayed or severed – there are a number of other related risks:

Increased fall distance:  leading edge applications often involve workers being attached at foot level which increases the distance of a fall compared with anchorage at shoulder height or above. 

Lock-up speed: Self-retracting lifelines (SRLs) react to a fall when the lifeline accelerates out of the housing, which is generally at a velocity of 1.37m/s. When SRLs are anchored at foot level, the lifeline does not achieve the required acceleration during a fall until after the user’s D-ring passes over the leading edge and below the level of the anchor. This means that the user will already have fallen about 1.52m before the SRL device will engage to arrest the fall.

Increased fall-arrest forces: Falling further means the impact on the body through the fall protection system will potentially be higher when the fall is arrested.  

Increased potential for pendulum hazards:  if a fall occurs when a worker is positioned at an angle to the anchor point, there is the danger that he will swing like a pendulum. This in itself poses impact dangers which are compounded if the lifeline saws back and forth across a sharp edge.

There are some measures that can be taken to reduce risks and prevent hazards in sharp and leading edge applications, which include using an energy absorber with standard SRLs, protecting edges with anti-wear/friction solutions and elevating anchor points. However, the safety industry now recognises that precise leading edge/sharp edge criteria need to be applied to the SRLs used in these applications. Specifically, it is recognised that lifelines not specially designed for foot level anchorage will generate forces far exceeding accepted safety parameters in the event of a fall. For that reason, leading and sharp edge components must work together to absorb energy, limiting the average arresting forces to 408 kg (4kN) or less.

HSE now states that users must ensure that equipment can be used in a horizontal plane and CE EN360 sharp edge certification sets out the requirements when SRLs are used with a shock absorbing unit. 

The Capital Safety range includes SRLs designed specifically for leading and sharp edge applications. These were initially introduced in response to the introduction by the American National Standards Institute (ANSI) of new standards on self-retracting devices, which included significant changes to their design and testing. Products include a 2.4m personal SRL designed for foot-level anchorage which is capable of stopping a fall within centimetres, providing increased protection at low heights, and a galvanised steel leading-edge SRL which is sad to be 35% stronger than standard cables.

Compliance is key to safety – both by the employer who must provide the right equipment and by the worker who must use it correctly.  Proper training is essential to ensure that workers fully engage with the need for fall protection measures and that they understand the unique hazards related to sharp and leading edges.  

WAH regulations require that anyone using personal PFPS should be properly trained by a ‘competent person’ who should be someone capable of identifying risks and with the authority to carry out measures to eliminate them. Major equipment suppliers offer training programmes that combine classroom training backed up by training and product manuals with hands-on training.