On multi-part reeved systems, if the parts of the line are evenly distributed on either side of the boom centerline, the boom twist will also be minimized. On single-line reeving, when the hoist line runs along the center sheave or on the sheave beside the centerline of the boom, the boom twist is minimized. Full chart ratings may only be applied when the boom tip is symmetrically rigged. This condition causes the boom to twist, which subsequently reduces the rated capacity of the crane. Unbalanced rope reeving occurs whenever the main hoist line is reeved to one side of the boom tip. Some questions to consider include: Is the jib erected or stowed? What type of jib is used? Are the outriggers extended properly? Are the tires properly inflated? What type of boom is used? What is the boom length? Where are the boom insert locations? What counterweights are used? Are they configured according to the manufacturer's specifications? What is the wire rope size and grade? What is the configuration of the hoist reeving? Most important, operators must know the configuration of the crane, ensure the configuration is correct, and use the appropriate load chart. Load chart ratings may only be applied if the machine is rigged according to the manufacturer's specifications. Some of these factors are described below. The first step in creating a lift plan is to understand the factors affecting the strength and stability of mobile cranes. It is likely that many fatalities could have been avoided with proper mobile crane lift planning. OSHA estimates that 89 crane-related fatalities occur each year in construction work, and many of these are high-profile events that receive a lot of adverse publicity. Mobile crane incidents can cause massive production delays, devastating property damage, and loss of life.
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