Rigid Rail Systems
fall arrest energy. When a fall is arrested on an HLL cable, the cable will sag and the input forces are amplified to the end anchorages as a result of the lever mechanics involved when the cable begins to move in the vertical axis. In order to protect the integrity of the anchorages and the other system components, the energy absorber will deploy or elongate, dampening these forces. Elongation of the energy absorber adds additional length to the HLL line in addition to the dynamic sag, which increases the overall fall distance. As a result, clearance management is a critical factor in HLL utilization. The use of intermediate or by-pass anchorages can help to limit the overall sag distance by reducing the free-span length of the HLL cable. The shorter sub-span lengths can greatly reduce the sag dis- tance and also reduce the overall fall arrest energy being transmitted to the end anchorages making for a safer and more effective system. Structural Horizontal Lifeline Systems may be installed in a permanent fashion in areas of frequent ingress and egress where periodic on contiguous fall hazards are present. They may also be erected in temporary applications, particularly in construction, to mitigate short term fall hazards. In either case, the versatility of these systems make them a popular choice in either circumstance. There are also kits available which feature a synthetic rope lifeline to make them lightweight and easy to install. These systems do have some short-comings, however. They typically require greater clearance as the synthetic rope tends to stretch under a fall arrest load. Additionally, the rope is susceptible to very rapid degradation and requires very careful inspection. In facilities where the structure may be insufficient to bear the arresting loads characteristic of HLL systems, Rigid Rail systems are often used (see next section). These are comprised of metallic rails or tracks which will have trolleys which serve as mobile anchorage connectors, allowing the user to walk from one end of the rail to the other while constantly tied off to an overhead anchorage, usually with Self-Retracting Lanyard. Systems of this type offer several key advantages. First, due to their rigid and inflexible nature, the loads are not amplified and are distributed, more or less evenly, to the nearest adjacent anchorage loca - tions. This means that they can be installed in more insubstantial structures and facilities without the additional of additional structural steel or other modifications. Furthermore, there is no dynamic sag, so the fall arrest distances are considerably reduced, meaning that they can be used in applications where very low clearances exist. This is particularly useful in general industry applications where four- foot trigger heights are the rule of thumb. When coupled with an effective Class A Self-Retracting Lanyards, Rigid Rails systems offer excep- tionally good protection to workers where linear fall hazards exist, and because the fall arrest distanc- es are so short, self-rescue and assisted rescue are generally very easy to execute, greatly simplify- ing the overall fall protection plan. As with Horizontal Lifelines, most of these systems can accommodate multiple workers, which helps to increase their usefulness and appeal.
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