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A team of riggers design and install the lifting or rolling equipment needed to raise, roll, slide or lift objects such as heavy machinery, structural components, building materials, or large-scale fixtures with a crane, hoist or block and tackle. Rigging comes from rig, to set up or prepare.
The crane's hook is kept level by automatically paying out enough extra cable to compensate for this. This is also a purely mechanical linkage, arranged by the reeving of the hoist cables to the jib over a number of pulleys at the crane's apex above the cab, so that luffing the jib upwards allows more free cable and lowers the hook to compensate.
Hoist atop an elevator. A hoist is a device used for lifting or lowering a load by means of a drum or lift-wheel around which rope or chain wraps. It may be manually operated, electrically or pneumatically driven and may use chain, fiber or wire rope as its lifting medium.
For lifting structures such as houses the hydraulic interconnection of multiple vertical jacks through valves enables the even distribution of forces while enabling close control of the lift. The screw version of the bottle jack works by turning a large nut running on the threaded vertical ram at the neck of the body.
The NIOSH lifting equation is a tool (now application) that can be used by health and safety professionals to assess employees who are exposed to manual lifting or handling of materials. [7] The NIOSH lifting equation is a mathematical calculation which calculates the Recommended Weight Limit (RWL) using a series of tables, variables, and ...
This leads to a mechanical advantage: the force needed to lift a load is only a fraction of the load's weight. At the same time, the distance the load is lifted is smaller than the length of chain pulled by the same factor. This factor (the mechanical advantage MA) depends on the relative difference of the radii r and R of the connected pulleys:
Casualty lifting: roll-and-lift method with a long spine board alternative for the position of the rescuers; note the arms that cross on the hips roll-and-lift with a flexible stretcher manual roll-and-lift method, or "spoon lifting", with three team members. The rolling methods can only be used on a casualty who does not have an unstable trauma.
Establishing the lifting anchor positions will influence the rigging arrangements used and therefore the static analysis of the rigging should be determined. Particular rigging configurations may be more suitable for particular job sites or lifting in place considerations, and the lifting design should denote the assumptions accordingly.