Lifting systems, rigging, and crane operations
Identify the load and every interface
A truss can carry attached platforms, lifting devices, and loose hardware in addition to its permanent steel. Determine what the crane will actually support. Locate the combined centre of gravity from mass distribution rather than geometric appearance. For a stated static model, a weighted position is the sum of each weight times its position divided by total weight. Support reactions can then be found by moment balance. An off-centre load need not divide equally, and a turning tandem lift may change shares as its geometry changes.
Every lifting component has its own function and rating. A compatible bow with an unverified shackle pin is not a verified assembly. Crowded eyes on a hook can bear at unintended locations. A sling's identification is necessary but does not prove it escaped heat damage. A below-hook device approved in one orientation is not automatically rated on its side. Select the actual hitch and arrangement from the appropriate manufacturer information, including the load's ability to resist forces introduced by the rigging.
Keep ideal statics separate from authorization
For two equal legs with angle theta above horizontal, the ideal static tension is load divided by twice the sine of theta. If a vertical component factor is supplied, divide the required vertical share by that factor to find tension. Reducing the angle above horizontal increases leg tension. Conversely, the supported vertical load is the sum of the legs' vertical components. A calculation of ideal force is not a working load limit and does not account for every dynamic or system restriction.
Reeving models also need clear assumptions. With ideal equal supporting parts, line pull is load divided by the number of parts, while rope travel is load travel multiplied by that number. A stated efficiency below one increases required input effort. Preserve the difference between kilograms of mass, kilonewtons of force, and kilopascals of average ground pressure.
Review the full path and configuration
Use the crane chart for the actual loaded radius, sector, counterweight, boom, and support arrangement. Apply its defined accessory deductions. If the problem prohibits interpolation, do not create an averaged capacity between listed radii. Boom deflection can change the loaded condition. A mat's outline is not necessarily its effective support area when it bridges a void.
Plan the load's entire travel envelope, blind areas, signaller handovers, and response to incomplete communication. Control-line paths must leave workers suitable positions and escape routes. Assembly and disassembly follow the specified support sequence; a binding or newly released pin may reveal residual loading. After the lift, document newly found damage so demobilization does not return a questionable component to service elsewhere.