The Importance of Measurements When Working at Height

In 2018, the number of accident files opened and accepted in relation to falls at a lower level was 4,750, which represents an increase of 328 files compared to 2017. In addition, the number of deaths following falls rose from 10 in 2017 to 15 in 2018, which represents almost a quarter of all deaths (24,2%).

Unfortunately, these statistics show that this type of accident continues to be very frequent and very severe, despite being considered one of the 9 hazards consisting a tolérance 0 of the CNESST. It is therefore necessary for employers to choose the most appropriate fall prevention measure for each situation in order to promote their use by workers.

Fall protection systems play an important role in preventing fall-related injuries for employees. There are many types of systems for this purpose: guardrails, movement limitation systems, fall arrest systems and the use of warning ropes, etc.

Falls can occur from ladders, permanent structures like roofs, temporary structures like scaffolding, and other types of work platforms. Fall protection systems are generally needed when workers are working at heights of 3m or more (sometimes they are needed even at height lower than 3m if other conditions apply).

Horizontal lifeline systems (HLLS) are among the solutions considered when fall prevention measures are limited or not applicable. A horizontal lifeline system is made up of several components. When designing such a system, each component must be taken into consideration.

A horizontal lifeline system is a fall protection system that uses a horizontal lifeline to which one or more workers could attach their individual fall arrest system by means of an appropriate connecting device.

The horizontal lifeline is only one component of a flexible system that runs horizontally from one end anchor to the other via anchor connectors and is made of a cable, a fiber rope, a steel cable, a fiber cable, or a metal rod and which ends with terminal connectors.

The anchor point is a strong connection point capable of withstanding the impact forces applied by a fall protection system or an anchor subsystem.

A worker attaches themself to the system consisting of the previously defined components via their safety harness (to the horizontal lifeline) with a retaining link, consisting of a webbing lanyard and an energy absorber (via components such as shackles).

When designing an HLLS, there are two things to consider:

• The effect of the fall arrest on the person
• The ability (resistance) of the HLLS to stop the fall

It is also very important to differentiate between the conformity of each component to the applicable standards and the behavior of the whole system. When components interact with each other in the event of a fall, then compliance of each component itself is necessary, but not sufficient to confirm compliance of the entire system.

From the start of the fall until the length of the restraint device is reached, the tension of the device is naught. Thereafter, it increases until the maximum arrest force is reached just after the fall. The calculations are made based on this force, to ensure that it remains within a range that the human body can bear. The values are specified in the Quebec Occupational Health and Safety Regulations (OHSR) and the Safety Code for the construction industry (6kN).

Regarding the resistance of the HLLS to stop a fall, the parameters to calculate are fewer thanks to the standardization of the components found on the market and the values predetermined by the standards and regulations. However, those to be calculated are essential and the integrity of the whole system depends on them, in particular the anchoring points of the system in a fixed structure for example. It is for this reason that the regulations required that the system be designed by an engineer.

References:

Statistiques Annuelle CNESST-2018

Travail sécuritaire-Nouveau Brunswick

Rapport R-902 RSST