Rigging, Slings, Hardware, and Load Handling
Rigging questions test whether you know the hardware, the inspection criteria, and the geometry that changes tension. Candidates must recognize wire rope slings, synthetic web slings, chain slings, shackles, hooks with safety latches, master links, swivels, turnbuckles, spreader bars, and equalizer plates. Know the difference between vertical, choker, basket, and bridle hitches and how each affects capacity. A choker typically reduces capacity compared with a vertical hitch; a basket hitch can increase it if the legs are vertical and the load is balanced.
Sling angle is a classic trap. Tension in each leg equals load divided by (number of legs times sine of the angle from horizontal). As the angle from horizontal decreases, leg tension rises sharply. A two-leg bridle at 30 degrees from horizontal carries more tension per leg than the same load at 60 degrees. Never exceed the sling's rated capacity for the hitch and angle used.
Inspection criteria: remove from service any sling with broken wires, kinks, bird-caging, heat damage, severe wear, missing tags, or damaged hardware. Hooks must have a functioning latch. Shackles must be rated and the pin fully engaged. Softeners protect loads and slings from sharp edges.
Worked rule of thumb: for a two-leg sling at 60 degrees from horizontal, each leg carries about 0.58 times the load; at 30 degrees, each leg carries the full load. Keep sling angles at 60 degrees or steeper when possible.