IRSST - Institut de recherche Robert-Sauvé en santé et en sécurité du travail

Study of Machine Safety for Reduced-Speed or Reduced-Force Work


The hazards associated with the moving parts of industrial machines are known to be the source of serious and even fatal accidents. The purpose of section 186 of the Quebec Regulation respecting Occupational Health and Safety (ROHS) is to provide guidance for machine maintenance, repair and adjustment work, further to section 182, which governs production work by prohibiting access to hazard zones and ensuring that moving parts are stopped when workers enter these zones. The focus of this research project was the application of ROHS section 186. The first objective was to assess the state of knowledge and recommendations in the literature on reduced-energy modes of operation, especially in terms of speed, force, pressure and temperature values. The second objective was to understand, through factory visits, how ROHS section 186 is being implemented.

A review of the literature revealed a wide variety of recommendations with respect to reduced-energy levels. The recommendations, chiefly based on standards and closely related to a specific context, are generally presented with accompanying supplementary conditions. A reduction in energy alone is often not sufficient to reduce the risk. Factory visits have shown that the various conditions prescribed in ROHS section 186 are sometimes hard to meet simultaneously. Safeguards, including the reduction of energy levels, are therefore a compromise between different constraints (related to job needs, the machine itself, production requirements, etc.) and risk reduction in order to prevent or reduce potential harm.

Last, the study revealed that reduced-energy values depend on many factors and that the wide variety of possible situations makes it necessary to conduct an in-depth risk analysis. The application of ROHS section 186 is therefore an integral part of the risk assessment and reduction process for tasks where workers have no alternative but to enter the zone where machine parts are in motion. The purpose of this process is to achieve a level of risk comparable to that contemplated in ROHS section 182, by taking protective measures that will compensate for opening a guard or starting up the machine. These protective measures are based on three principles: reduce harm, increase the possibility of avoiding harm and reduce exposure to the hazard. Yet the issue of determining reduced-energy levels remains unresolved. Generally speaking, when the literature recommends values, if the situation in question corresponds exactly to the context described in the literature, then designers may use these same values. On the other hand, when no reference is available, the determination of a tolerable energy level must be based on more extensive thought and analysis. Only a thorough comparison of the context of the proposals made in the literature and that of the real situation will allow extrapolation of the recommendations to comparable, but not identical situations. A risk analysis must be conducted. The study identified some reference points or factors that will provide guidance to designers and users as they analyse specific cases and try to decide on the most appropriate values for reduced speed, force, kinetic energy and contact pressure.