Rigging, Hoisting and Site Preparation
This domain tests moving heavy equipment and cylinders without injury: load assessment, sling angle effects, hardware inspection, lift planning, cylinder handling, and preparing a site so the work can proceed legally and safely.
Load and rigging fundamentals
- Use the manufacturer's weight and identify the centre of gravity. Never lift an appliance by its gas manifold, regulator, CSST, vent connector or an unmarked point.
- For a two-leg bridle, tension per leg = (W ÷ 2) ÷ sin θ, where θ is the angle from horizontal. At 60° each leg carries about 0.58 W; at 45° about 0.71 W; at 30° about 1.0 W. Choke and basket hitches reduce capacity, as does a small D/d ratio.
- Hardware: grade 80 or 100 chain, forged shackles, hooks with functioning latches, certified synthetic slings. Remove slings with cuts, broken wires, heat damage, chemical damage or a missing tag.
- Lift plan: barricade the area, use tag lines, one signal person, hand signals or radio, and read the capacity chart at the actual radius.
- Cylinders: upright and secured, valve cap on during transport, moved by cart or cradle - never sling a cylinder by its valve. Propane storage limits and separation distances come from B149.2.
- Site preparation: utility locates before excavation, shoring or sloping for trenches, housekeeping, temporary heat with proper venting, fall protection at roof penetrations, and coordination with other trades.
Worked example
A 1,200 lb boiler is lifted on a two-leg bridle at 45° from horizontal. Tension per leg = (1,200 ÷ 2) ÷ sin 45° = 600 ÷ 0.707 = 849 lb. Select slings and shackles rated well above that figure, include the weight of the spreader bar and rigging, and confirm the hook latches. If the same bridle were flattened to 30°, each leg would carry 1,200 lb - a 41% increase - which is why the angle must be measured on site rather than assumed from the drawing.
Traps that cost marks
Ignoring sling angle when estimating capacity; using a sling with a missing tag; lifting a propane cylinder by its valve; digging before locates are complete; leaving an open floor penetration unguarded; and using gas piping as a lifting point.