Lifting plans, rigging and load control
Lifting plans, rigging and load control is where the paperwork meets the hardware. The exam checks that you can read or write a plan that matches the real lift, calculate sling tension honestly, and control the load from pick-up to set-down.
What a plan contains
Load mass and centre of gravity, lift points, rigging arrangement and working load limits, crane position, the chart used, worst-case radius, ground conditions, the travel path and landing area, environmental limits, roles and signals, the exclusion zone, and contingency for a power or equipment failure. Complex or critical lifts, commonly those above about 75% of chart capacity, involving two cranes, personnel, live plant or the public, poor ground or unusual rigging, need a documented study and sign-off.
Rigging mechanics
- Sling tension = load / (legs sharing x cos of half the included angle).
- Ratings already assume unequal sharing: a four-leg sling is generally rated on two legs carrying, so read the tag rather than dividing by four.
- Chokes and baskets derate the sling; add edge protection and check the D/d ratio on rope slings.
- Shackle pins fully seated, no side loading on the bow.
- An off-centre centre of gravity makes the load tilt and one leg take more.
Worked example
A 6 t load on a two-leg sling with a 90 degree included angle. Half the included angle is 45 degrees, so tension per leg = 6 / (2 x cos 45) = 6 / 1.414 = 4.24 t. Select slings rated at least 5 t for each leg. The common error is 6 / 2 = 3 t and choosing 3.2 t slings, which overloads them by more than 30%.
Traps that cost marks
- Dividing by the number of legs instead of using the angle factor.
- Measuring the angle to the vertical rather than the included angle between legs.
- Leaving rigging weight out of the crane capacity calculation.
- Returning a damaged sling to service, or standing in the bight.