CSA - PLUS 1156
Fall-Arrest Systems - Practical Essentials
|Publication Date:||1 January 2000|
Fall protection has developed during the past twenty-five years into an independent, cohesive, and relatively complex field of safety engineering. This complexity is especially apparent in fall-arrest systems. These systems, when used correctly, arrest accidental falls by workers in situations where preventing falls is not feasible.
The fall event is dynamic in nature. Therefore, all the phenomena that take place during the arrest of an accidental fall by a fall-arrest system (FAS) are also dynamic. During the fall-arrest action, every component of the fall-arrest system is subject to momentary shock load, including the user's harness, shock absorber, lanyard, fall arrester, vertical lifeline, or self-retracting lifeline/lanyard. So too is a horizontal lifeline, an anchorage, and all the connecting hardware. Each and every component of the fall-arrest system must be able to withstand the dynamic forces occurring in the FAS with the required margin of safety.
These dynamic forces are always greater than the weight of the person falling. This is because of the sudden deceleration of the falling mass. The forces involved are much greater than the static weight of the fall victim, increasing by a factor as low as two when free-fall distance is negligible, to four if a shock absorber has been employed, to thirty and higher for some horizontal lifelines. The most common standard mass for a fall victim is 100 kg or 220 lb. The permissible shock load acting on the fall victim is limited by fall protection regulations in the United States and Canada to 8 kN (1800 lb).
A fall-arrest system is the very last line of defence against fall hazards. The first and best defence is to eliminate the hazards, if at all possible. Unfortunately, in many cases this is prohibitively expensive and therefore not feasible. The second defence is to prevent a fall, through the construction of barriers, guardrails, covers, and so on. This method is widely practised, relatively inexpensive, and quite efficient.
The third defence, fall arrest, becomes necessary when the first two approaches are not feasible. In such a case, it is accepted that a fall may occur, and employers provide an FAS to catch a falling worker in mid-air and bring the individual safely to a complete stop. The task is not always simple, particularly when safety nets are not practical and only a personal fall-arrest system may be used.
Detailed knowledge about fall events tends to be highly specialized. The course of studies in technical colleges does not yet deal with the engineering issues related to dynamic forces in fall-arrest systems and to the plastic (permanent) and elastic (temporary) deformation of FAS components. There has been quite a bit of research on and documentation of the medical aspects of the exposure of the human body to transitory deceleration, as these matters are directly related to the safety of flying personnel. However, these matters are taught only as specialty courses at medical schools and in the field of biomechanics. Regulations and technical standards for fall protection are also very complex, even for safety personnel, as anybody would agree who tries to digest ANSI Standard Z359.1 or the Subpart M - Safety Standards for Fall Protection in the Construction Industry (1926.500-503) issued by the U.S. Department of Labor.
Even though the regulations require that users of fall arrest systems be properly trained and periodically retrained, few users will be fall-protection specialists. PLUS 1156 is written with these non-specialists in mind. If FAS users follow the ten essential principles presented in this guide, their fall-arrest systems will safely stop most falls. As well, their employer's fall-protection program will prove itself appropriate and efficient.
The rules presented in this guide are simplified. They provide adequate direction for a person trained in fall protection, but they are not the only rules in fall-protection engineering for safety professionals. FAS designers and structural engineers who evaluate the strength of available anchorages must be familiar with a vast array of technical, legal, medical, and other rules.
Ten Essential Principles for Users of Fall-Arrest Systems
Here are ten simple and basic rules for using an FAS. You should follow them at all times.
1. Inspect your equipment before every use.
2. Don and adjust your harness properly.
3. Use your shock absorber or your shock-absorbing lanyard whenever possible.
4. Connect all components of your FAS using only compatible connecting hardware.
5. Attach your FAS only to a suitable anchorage.
6. Keep your fall distance to a minimum.
7. Consider the conditions of your workplace when choosing your equipment.
8. Care for your equipment as you would care for yourself.
9. Know the rescue procedure and equipment in case you should fall.
10. Be properly trained to use any fall protection equipment.