When using active fall protection systems such as travel restraint and fall arrest systems, it is very important for users to understand the provided systems and equipment.
Complete systems should be provided with user instructions and system performance. If users do not know how the systems behave, they may not be able to understand the severe consequences of improper use. The following information should help everyone to understand the intricacies of fall protection system performance.
First of all, what is the difference between Travel Restraint and Fall Arrest? Travel restraint, commonly referred to as fall restraint, should prevent users from falling, whereas fall arrest mitigates the risk and severity of a fall. Travel restraint is usually accomplished by specifying a lanyard length that will keep users away from the edge. However, in some cases users are trained to adjust lanyard lengths to prevent them from reaching the edge. A good rule of thumb is: if your lanyard allows you to stand within 2 ft of the edge, you may not be set up for travel restraint.
Okay, that all makes sense, so what is clearance? There are two types of clearance; required clearance and available clearance. Available clearance is the distance required between a reference point and the nearest object below that a falling worker could impact. Required clearance is the distance from a reference point to the toes of a fallen worker after they have fallen. Typically, designers will either use the anchor point or the surface the user is standing on as a reference point. These are both suitable reference points; however, when an anchor is located overhead, it may be difficult to spatially understand how much clearance is required below it.
Okay, that all makes sense, so what is clearance? There are two types of clearance; required clearance and available clearance. Available clearance is the distance required between a reference point and the nearest object below that a falling worker could impact. Required clearance is the distance from a reference point to the toes of a fallen worker after they have fallen. Typically, designers will either use the anchor point or the surface the user is standing on as a reference point. These are both suitable reference points; however, when an anchor is located overhead, it may be difficult to spatially understand how much clearance is required below it.
Determining clearance requires designers to determine:
How far the worker will fall before the slack in the system is taken up (i.e. before the lanyard becomes tight and force is applied to the anchor). This is called free fall.
How much a personal energy absorber will deploy – this is based on user weight, free fall distance, and equipment used.
If there will be any deflection at the anchor. For Horizontal Lifeline Systems, this includes stretch and sage of the lifeline. For rigid anchors, this includes deformation.
A safety margin is included as required by the design standards to account for any unknown variances from the assumed inputs.
Another detail that is important to understand is the arrest force per user. This is the maximum impact on a worker if they fall. This is limited to the force the personal energy absorber is rated for only if the energy absorber doesn’t bottom out (deploy fully). How can you make sure that you don’t do this? Use the equipment specified by the designer, and always verify you will not see a free fall greater than indicated in the performance summary. This may mean that you have to adjust the length of your lanyard several times throughout the day, or that you must use a different lanyard than what you have in your kit.
The load on the system is given in the system performance details as well. If this is a horizontal lifeline system our designers calculate the load transfer from the worker to the anchors through the cable. For rigid anchors, the applied force is typically the same as the impact force on the user. If users decide to use equipment that is not certified for use with the system, they risk overloading the anchors or connections.
Our team of specialist engineers perform an analysis for each and every system we design, providing this information in a clear and concise manner. Contact us today to learn how we can ensure you have all the information you need to make a safe environment for work at heights.
Need Additional Help?
Whether your project is a self-installation, supervised installation, or you require turnkey services, High Engineering Fall Protection specialists are standing by to assist you. Get started by requesting a quote or contact us at (403) 287 0475.