Horizontal Systems Defined
This means that if you are working at height attached to an HLL and you fall, your fall must be completely arrested before you hit something on a lower level (this may or may not be the ground). The distance that you fall before your Personal Fall Arrest System (PFAS) begins to arrest your fall cannot exceed 6 feet - and the distance between activation of the PFAS and total fall arrest cannot exceed 42 inches (in most cases). This is important with regards to the DESIGN of a horizontal system, and strongly reinforces the fact that simply stringing a cable between two end points does NOT constitute a true Horizontal System . OSHA 1926.502(d)(8) states : ‘Horizontal lifelines shall be designed, installed and used, under the supervision of a qualifiedperson, aspart of acompletepersonal fall arrest system,whichmaintainsasafety factor of at least two’ .This guidance is not exactly, comprehensive, so there is quite a bit of variability in themarketplace. Types of Horizontal Lifeline Systems There are two basic types of Horizontal Lifeline Systems: Architectural and Structural . Architectural Systems are typically roof-mounted cable systems utilizing short post anchors. They are most often run down a roof ridge, or around the perimeter of a flat roof and may be used for either restraint or for fall arrest. In an effort to protect the roof structures to which they are attached, these systems typically utilize deforming anchorage posts, which absorb fall arrest energy and mini- mize the transmission of these forces to the roofing substrates.
Installations of Architectural Horizontal Lifeline Systems are almost universally permanent installations, as penetrations of the roofing surface are required. In most cases, they will have to be inspected, and potentially serviced, on an annual basis as a result of their constant exposure to the elements in all extremes of weather. For these reasons, the most effective and efficient systems are utilized for restraint, so as to reduce the opportunity for damage to be done to the building in the event of a fall. These are most effectively utilized with Vertical Lifelines and Rope Adjustors as opposed to Energy-Absorbing Lanyards or SRL’s. Well-disciplined use of VLL’s will greatly ex - tend the serviceable life of these systems. Structural Horizontal Lifeline Systems are generally utilized in construction environments or inside of fixed facili - ties. These systems can be mounted in a variety of different ways. In steel erection, they can be strung between columns, six to eight feet above the walking-working surface, in order to provide an overhead anchorage. They can also be installed on free-standing stanchions, which can allow these systems to be used when vertical structures may not exist in order to provide anchorage locations.
Structural Horizontal Lifeline Systems will rely on in-line energy absorbers to dissipate some of the
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