Basic Rigging (RB) common mistakes
Basic Rigging (RB) · Understand the traps and how to avoid them.
Computing sling tension by dividing the load weight by the number of legs without applying the horizontal angle factor (multiplier), so a two-leg bridle at a wide included angle is treated as if each leg carried half the weight.
Candidates memorize 'divide by the number of legs' as a shortcut and forget that tension rises as the sling angle from horizontal decreases; the geometry adjustment is abstract and easy to skip under time pressure.
What to do instead
Write the formula on scratch paper before solving: tension per leg = (load weight / number of legs) x length of leg / vertical height, or equivalently divide by the sine of the angle from horizontal. Always compute the angle factor first, then multiply, and sanity-check that tension is always greater than the plain share of weight.
Estimating a load's weight from its visible size or from memory of 'typical' material weights instead of computing volume times unit weight from a known table, and omitting attachments, contents, or packaging.
Candidates rely on a single remembered number (for example steel at 490 lb per cubic foot) and misapply it to hollow, bundled, or mixed-material items; they also forget that rigging hardware, pallets, and residual contents add to the total.
What to do instead
Break the load into simple geometric shapes, compute each volume, multiply by the correct unit weight for that specific material, then add a separate line for rigging, packaging, and unknown contents. Round up and treat the result as a minimum, not an exact figure.
Assuming the center of gravity is at the geometric center of the load and rigging to that point, causing the load to tilt when lifted.
Symmetric appearance is persuasive, and candidates rarely check for heavy ends such as a motor mounted on one side of a skid or fluid settled in one compartment.
What to do instead
Perform a deliberate center-of-gravity check: look for asymmetries, test-lift a few inches, observe which end dips, and adjust attachment points or add a tag line before the full lift. For multi-piece assemblies, calculate the combined center of gravity from component weights and distances.
Reading the working load limit from the sling's color code or from the tag's headline number without confirming the hitch type, leg configuration, and angle that the rating assumes.
Color codes and single numbers are memorable, while the qualifying notes (vertical versus choker versus basket, single leg versus multi-leg assembly, angle derating) are buried in fine print and easy to overlook.
What to do instead
Read the entire tag and identify the hitch before trusting any number. Recompute the capacity for the actual configuration: apply the choker reduction, the basket efficiency, and the angle multiplier, and treat the lowest-rated component in the system as the controlling limit.
Using a damaged sling or one with an illegible or missing tag because it 'looks fine' and the lift is small.
Defects such as broken wires, heat damage, crushed core, or a single cut jacket strand are subtle, and candidates fear slowing the job or being seen as uncooperative.
What to do instead
Apply a fixed pre-use sequence every time: tag present and legible, then the full length inspected for broken wires, cuts, burns, chemical damage, and distortion. Any doubt means remove from service and tag out; the authority to reject a sling is part of the job, not an obstacle to it.
Confusing a knot with a hitch and tying a knot in a sling or rope that will be load-bearing, which cuts capacity drastically.
Knots are familiar from general rope work, and candidates transfer that habit to rigging without realizing a knot can reduce rope strength by roughly half and cannot be inspected internally.
What to do instead
Use knots only for non-load-bearing tie-offs. For lifting, use recognized hitches (vertical, choker, basket) or approved hardware, and if a knot is unavoidable in a utility line, derate heavily and never use it as the primary load path.
Rigging a choker hitch so the sling chokes on itself rather than around the load, or placing the choke where it will slide toward the load's balance point during the lift.
The choke looks correct at ground level, and the tendency of a choked sling to creep along a tapered or smooth load is not obvious until the load is airborne.
What to do instead
Seat the choke snug against the load with the eye clear of the standing part, position it so the load's weight tightens rather than loosens it, and add a second attachment or tag line where slippage is possible. Verify the choke is fully closed before lifting.
Standing inside the fall zone or placing hands on the load to steady it while it is being lifted.
The instinct to guide the load by hand is strong, and the swing radius or potential drop path is not visualized before the lift starts.
What to do instead
Before the lift, walk the area and mark the fall zone and swing radius, then position everyone outside it. Control rotation and sway with tag lines from a safe distance, never with hands or body weight, and keep all personnel clear until the load is landed and stable.
Using hand signals that are approximate or improvised, or continuing a lift when the signal is unclear or comes from more than one person.
Candidates recall the general motion but not the exact standard signal, and on noisy sites people default to waving or shouting, which the operator may misread.
What to do instead
Learn the standard signals to the exact motion and practice them until they are automatic. Establish one designated signalperson before the lift, stop immediately on any unclear or conflicting signal, and use radio communication with agreed words where distance or visibility is a problem.
Skipping or rushing the lift plan and pre-lift checklist, going straight from 'the load is rigged' to 'take it up' without confirming capacity, clearance, landing point, and emergency stop arrangements.
Routine lifts feel repetitive, so the plan becomes a formality; time pressure and confidence in past success replace verification.
What to do instead
Run a short, fixed pre-lift briefing every time: load weight and center of gravity, rigging capacity versus load, path and clearances, landing and blocking, tag line assignment, signalperson, and stop criteria. If any item cannot be confirmed, the lift does not start.