LAUSR

Abstract Industrial machines are known to possess many hazards. One machine safety design requirement found in the machinery directive in Europe, national or provincial legislation in North America, as well as national and international safety of machinery standards is the control mode for maintenance when guard or protective device has to be displaced or removed. One of the conditions is that the control mode permits operation of the hazardous elements only in reduced risk conditions. This condition presents some challenges to designers and users alike. What are considered reduced risk conditions is open to interpretation. The objectives of this study were to identify values for safe reduced speed, safe kinetic energy and safe contact pressure from the literature and from enterprises and to identify the factors influencing the choice of values. It was found that values for reduced speeds, force, energy, contact pressures varied widely. Industrial visits showed that enterprises use reduced speeds by switching to the reduced speed mode of operation without applying the other required conditions. Machines were modified to incorporate this mode of operation indicating some design problems. Some factors were identified which could guide the choice of values when the information is missing from standards or other documents. When a safety standard exists for a particular machine and that the values are specified in the standard, designers and users can use those values. However, if the machine has no safety standard, a risk assessment is needed before deciding which values to use.