Rigging, hoisting, positioning, and cranes
Plan the complete lifting system
A lifting arrangement includes the load, its centre of gravity, lifting points, slings, connectors, hook, crane or hoist, ground support, travel path, landing support, and communication. Establish actual load information before choosing gear. A component may have different ratings for different hitches, directions, and configurations. A clean appearance or physical fit does not establish a working load limit. Preserve identification, inspect equipment against the applicable criteria, and remove questionable components for proper assessment. Knots, twists, unauthorized pins, tip loading, or improvised repairs are not substitutes for a rated arrangement.
A freely suspended load tends to settle with its combined centre of gravity below the suspension point. Uneven mass can produce unequal reactions at two lifting points. For a simplified static beam, use moment balance to determine shares rather than automatically dividing by two. Four connected legs likewise do not guarantee equal sharing. The engineered configuration and actual stiffness and geometry matter.
Understand angle and unit conventions
For a symmetric two-leg static bridle with angle theta above horizontal, each leg tension is W divided by twice sin theta. If the angle is measured from vertical, use the corresponding cosine relationship. A smaller angle above horizontal generally increases tension. Do not silently change angle references. Calculated ideal tension is not itself permission to lift; apply the actual manufacturer's ratings, configuration restrictions, dynamic considerations, and approved plan.
Mass and force are different. If the problem supplies gravitational acceleration, force in newtons equals kilograms multiplied by metres per second squared. One kilonewton is one thousand newtons. An outrigger bearing estimate uses reaction divided by effective bearing area. A level surface is not proof of adequate soil support, and underground trenches or voids can invalidate simple assumptions.
Match crane configuration and control movement
Operating radius is the horizontal distance from the rotation centre to the loaded hook line, not boom length or hook height. Use the chart for the actual boom, counterweight, outriggers, sector, and other stated conditions. Apply its defined gross-load deductions correctly. Large-area panels can be wind-sensitive even at modest mass. Coordinate blind lifts with a designated signalling system, respect emergency stops, and stop safely if required communication is lost. A trial lift can reveal slipping or imbalance. Before unrigging, confirm stable load transfer and required restraint. Crane assembly, multi-crane lifts, and electrical approach work require the appropriate specific plans rather than guessed universal limits.