TOP 5 CONSIDERATIONS WHEN CHOOSING AN OVERHEAD FALL ARREST SYSTEM
There are a variety of ways to address safety at height. The key to choosing the right form of fall protection requires a clear understanding of two main factors (1) the risks & hazards associated with the work at height and (2) the dynamic and technical differences between solutions that exist to address those risks & hazards most effectively.
Once an overhead fall arrest system has been determined to be the best method to protect your work at height needs, there are two system types…Rigid Rail and Horizontal Lifeline (HLL).
When properly designed, engineered, installed, and maintained, Rigid Rail and Horizontal Lifeline systems are both capable of providing reliable and compliant fall protection. But which one is better? Which one is right for you?
These are the Top 5 considerations that you should consider when selecting the right type of overhead fall protection for your application.
The biggest driving factor when selecting a system is typically its cost as you may only have a certain budget to work within. Cost is naturally the first factor that goes into the decision-making process. While it is often true that HLL systems have a lower cost of entry than Rigid Rail systems, there are multiple additional factors that determine initial system cost and that ultimately influence the cost of ownership over the lifecycle of the system. However, some budgets and facilities are ideal for a HLL system.
# 2 Facility Layout
What most don’t consider is their facility layout, which plays a huge part in how the system will be installed, the working height, how the system performs, and the cost of the system. The roof of a typical facility is made up of frame rafters and purlins, and this is the structure that the fall arrest system will be installed onto.
Rigid Rails are versatile and can be installed onto either the purlins or the frame rafters, in any 360 degree direction. HLLs on the other hand, are usually only installed onto the frame rafters, unless additional structure is installed between two sets of frame rafters to allow for installing perpendicular to the purlins. This additional steel may end up making the fall arrest system more costly than just a standard Rigid Rail!
# 3 Working Height
One big disadvantage of HLLs is the larger fall clearance distance required, due to what is known as sag, as HLLs are not rigid like their counter part Rigid Rails. There are two types of Sag, Initial and Dynamic. Initial Sag comes from the weight of the system trolley, Self-Retracting Lifeline (SRL), and the weight of the wire rope. You can see initial sag in the figure below. When you add the weight of a falling person, you get the dynamic sag as seen in the figure below. Rigid rails by design do not have these sags and as such can be used in lower clearance areas.
#4 Worker Falling Safety
Both rigid rails and HLLs act as a fall arrest system, which means a worker can still fall but the fall protection system will stop the worker from hitting the ground. However, falling when using a HLL system comes with its own complications. Firstly, if a worker were to fall, the dynamic sag in a wire rope system will cause the trolley to roll into the middle of the HLL span, which in turn means the worker is exposed to a swing fall and potentially additional injuries. Lastly, if you have multiple workers using the HLL at the same time and one were to fall, all the slack in the system is removed and a sudden pull on the wire rope occurs resulting in the other workers being put at risk.
# 5 Rescue Plans
Rigid Rail and HLL systems should be regularly inspected, maintained, and repaired by a competent person to ensure the system is in good working order. This inspection is typically carried out annually, with a full engineering design review conducted every five years to ensure that the systems meet or exceed local and federal regulations. Should a fall occur both types of systems will require an inspection by a competent person to check for damages. Rigid Rail Systems typically will withstand a fall with minimal, if any, damages. However, Horizontal Lifeline Systems will often need part replacements (energy absorber, tensioner, wire rope, etc.) and in some cases you could end up having to replace the entire system!
The High Engineering team has a firm grasp of OSHA, CSA, ANSI standards and has decades of experience designing and installing fall protection systems for a range of applications including Rigid Rail and Horizontal Systems. Contact us with your questions and get help with choosing the perfect system!