Leading edges — an under-recognised hazard
By Rick Millar, Technical Manager, Capital Safety Australia & New Zealand*
Wednesday, 07 October, 2015
The level of awareness about the need for personal protective equipment (PPE) has been greatly improved in the past 10 years, leading to much higher compliance. The supply of much more comfortable equipment and improvements in technology brought about by various manufacturers has only served to improve that compliance.
As in most cases, however, it is not only the actual PPE that needs to be considered when working on a site; it is the environmental factors at play that can affect the actual performance of the PPE when called on to keep people safe.
Construction workers who recently worked on a US football stadium grew to know about the real importance of this — specifically fall protection — when they were working at height. They also had to be sure to be using the appropriate equipment and use it properly to stay safe.
Two of the construction workers came to know the value of quality fall protection equipment and proper training firsthand: the first fell from a steel beam, six stories above ground. Less than two months later, another worker slipped from a beam and fell. Both escaped injury and possible death because of their fall protection equipment. Fortunately, these workers not only walked away after these accidents — remarkably, they were able to go back to work the same day.1
But what if they had been using the wrong products, or the wrong anchorage points, or had failed to take into account swing fall hazards or sharp-edge hazards?
Those workers may never have returned to work!
Many personal fall arrest systems rely on lifeline materials to perform when exposed to less-than-ideal conditions. But there are some applications where use of the wrong product — for example, where a lifeline contacts with a sharp edge — could have catastrophic results.
Product testing and certification organisations in the US and around the world, including the American National Standards Institute (ANSI), the Canadian Standards Association (CSA) and European Standards (CE), have been re-examining how lifelines in fall protection systems perform when subjected to these 'sharp edge' circumstances. They've also placed a new focus on 'leading edge' applications. Through this analysis, they have concluded that these two environments are unique in fall protection and involve increased risks due to the lifeline cutting, fraying or becoming otherwise compromised.
Understanding leading and sharp edges
Sharp edge
A sharp edge is one that, for practical purposes, is not rounded and has the potential to cut most types of lifelines. The ANSI standard for sharp edges involves testing the fall arrest device's lifeline over a piece of steel bar with a radius of no more than 0.127 mm. If the lifeline is cut or severely damaged, the device fails the test and does not comply with ANSI. European Standards are similar, though their sharp-edge test is slightly less rigorous. In both cases, however, the performance requirements that these lifelines are required to meet are well in excess of those for a regular lifeline.
Left image: A sharp edge 0.50 mm or greater typically found in I-beams and other similar materials. Right image: An extremely sharp edge 0.13 to 0.50 mm, typically found in roof sheeting and other similar materials.
Leading edge
To visualise a leading edge, imagine a worker installing steel decking on a new building. Now imagine the worker's fall protection system is anchored at foot level behind him, in the absence of any alternative anchorage location above them. As the worker moves out and away from the anchor point while installing the decking, the worker is exposed to a potential fall over the edge of the building or the edge of an elevated platform.
Risks of leading- and sharp-edge applications
In sharp-edge applications, the primary risk is the lifeline can be frayed or severed. Examples of other related risks with falls over leading edges include:
- Increased fall distance: When workers are attached at foot level, as they often are in leading edge applications, they will fall further than they would if they were anchored at shoulder height or above. Image 1 demonstrates the sequence of events that happen when a worker falls off a leading edge, and why a worker needs additional clearance. The required clearance when anchored at foot level varies by product, so make sure to reference the product instructions.
- Lock-up speed: Self-retracting lifelines react to a fall when the lifeline accelerates out of the housing at a certain velocity, generally about 1.3 m/s. When self-retracting lifelines 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 the user has already fallen about 1.6 m before the self-retracting lifeline 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. This is why many leading-edge and sharp-edge-rated products contain additional energy-absorbing devices.
- Increased potential for swing hazards: If a worker falls and is off to one side, they may swing like a pendulum. While this is in itself dangerous, the danger is compounded if the worker is on a sharp edge and the lifeline saws back and forth across that edge.
New standards call for different equipment
Previously, the industry made attempts to prevent hazards in sharp- and leading-edge applications. These solutions included attaching an energy absorber to standard self-retracting lifelines; protecting edges with antiwear/friction solutions; and elevating anchor points. While these efforts have been helpful, many organisations have now incorporated leading-edge/sharp-edge criteria into their standards or are working towards doing so. While these requirements are yet to appear in Australian and New Zealand Standards, they have been updated in ANSI, CSA and European Standards defined by the CE testing standards for self-retracting lifelines (SRLs).
In August 2012, ANSI released a new standard — ANSI Z359.14 on self-retracting devices (SRDs)2 — to address leading-edge or sharp-edge applications for SRLs. The US OSHA Standard Z359.14 includes significant changes to the design and testing of leading-edge (LE) SRLs. It provides a baseline for manufacturers to test their products against, in order to ensure they are safe and compliant.3 It also requires manufacturers to provide new information in product user instructions and on product markings.
Although these requirements are yet to appear in the Australian and New Zealand Standards, the risks to the lifeline remain the same. A sharp edge in Australia is the same as a sharp edge in the USA!
Products to deal with leading- and sharp-edge applications
Following the North American and European standards changes, manufacturers have responded by designing products for these applications. Lanyards with cut-resistant rope can be used, along with additional protections such as wear sleeves or the use of edge protection products to reduce the risk of fraying and scissoring.
Additionally, some manufacturers now make self-retracting lifelines with high-strength webbing and wire cable materials to overcome the excessive forces being applied to the lifeline in a leading-edge application.
Both compliant equipment and training needed to keep workers safe
While equipment specifically designed for leading edge applications is needed to keep workers safe, it's only effective if crews understand how to use it and why they need it. Proper training is essential to ensure workers fully engage and understand the hazards related to sharp- and leading-edges. Your training provider should be able to address the risk management process around leading-edge applications.
Greater awareness also leads to greater safety
Fall protection experts agree that in addition to complying with the applicable standards, keeping workers safe at height also involves a much greater awareness of the fall protection risks that exist in particular applications, such as sharp- and leading-edge applications. This is particularly true for workers who have worked in sharp- and leading-edge environments for many years and have developed habits over time that may not be the safest practices in today's environments.
All workers and their employers need to be up to date on the latest technology — including products, applications and training — so that the appropriate equipment is used properly for the right application. In sharp- and leading-edge work, using a traditional product anchored at foot level may increase the risk of injury and create a false sense of security. Always consider these environmental factors when making a product selection to ensure safety intentions are carried through to effective implementation.
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