Safety of rope-guided conveyance systems

The guide rope factor of safety (FOS) currently set in regulations in various countries is unduly conservative and constrains the maximum attainable depth for shafts using rope guides. It limits the amount of guide rope tension that can be imposed, which is important for controlling the lateral motion of conveyances. A lower FOS would lead to more constraint of lateral conveyance motion and therefore safer winding, but this implies a design trade-off of apparent rope safety versus conveyance guidance safety. This paper considers the safety of rope-guided shaft systems and questions whether the above trade-off is appropriately set. Rope safety, the role of guide ropes, and constraints on increasing guide rope tension are discussed. Precedents for review of rope FOS are recalled. The paper provides a motivation for reducing the regulated guide rope static FOS, which will give designers more flexibility in configuring rope-guided systems and will reduce capital costs—potentially significantly if the design is on the boundary of these constraints. Following precedents for a lower rope FOS, it is proposed that, if adopted, this reduction is made with the obligation to meet a code of practice for guide rope installation, inspection, and maintenance.