Basic Rigging (RB) cheat sheet

OSHA 29 CFR 1926 Subpart CC governs cranes and derricks in construction; 1910.184 covers slings and 1910.176 covers materials handling in general industry.

Sling removal criteria (1910.184): chain sling links with cracks, stretches, or bent/worn surfaces over 15% of link thickness are removed from service.

Wire rope sling removal: 10 or more randomly distributed broken wires in one rope lay, or 5 broken wires in one strand of one lay, requires removal.

Synthetic web sling removal: snags, punctures, tears, cuts, embedded abrasive material, or broken/worn stitching disqualify the sling.

Rated capacity of a sling is based on a design factor of 5 for most slings; chain slings use a design factor of 4 in overhead lifting.

The rigger's role in the lift plan: verify sling capacity, hitch type, load weight, and center of gravity before the lift begins; the lift director authorizes the lift.

Never rig to a crane's hoist hook latch or tip; the load must bear on the saddle (bowl) of the hook, not the point.

A qualified rigger is defined in 1926.1401 as a person who meets the criteria for qualification through training and experience in rigging.

The safe working load of a wire rope sling in a vertical hitch equals the rope's vertical load rating; capacity is reduced by the choke or basket configuration used.

Shackle capacity is determined by the pin and body size; a screw pin shackle's pin must be fully seated with no gap before loading.

Chain sling capacity is rated per leg; a two-leg sling at 60 degrees from horizontal carries 1.732 times one leg's vertical capacity.

Synthetic round slings use color-coded capacity bands: a common convention is purple for 1 ton, green for 2 tons, yellow for 3 tons, gray for 4 tons, red for 5 tons, brown for 6 tons, blue for 8 tons, orange for 10 tons.

Master links and end links must be rated for the sling assembly; a master link's rated capacity must equal or exceed the sum of the leg capacities at the hitch angle.

Eye bolts are derated for angular loading: a 45-degree pull reduces capacity to about 70%, and a 90-degree side pull to about 30% of the rated load.

Wire rope clips: use the correct number per rope diameter and spacing; the U-bolt goes over the dead end of the rope, not the live end.

A turnbuckle, come-along, or chain fall used for lifting must be rated and marked for overhead lifting; consumer-grade hardware is not acceptable.

Vertical hitch: one leg carries the full load; capacity = single-leg vertical rating.

Choke hitch: the sling passes around the load and through its own eye; capacity is typically 75-80% of the vertical rating because of the choke angle.

Basket hitch: the sling passes under the load and both eyes attach to the hook; capacity is roughly double the vertical rating when legs are vertical.

Two-leg sling at 60 degrees from horizontal: total capacity = 2 x leg rating x sin(60) = 1.732 x leg rating.

Two-leg sling at 45 degrees from horizontal: total capacity = 2 x leg rating x sin(45) = 1.414 x leg rating.

Two-leg sling at 30 degrees from horizontal: total capacity = 2 x leg rating x sin(30) = 1.0 x leg rating; the angle factor shrinks sharply as slings flatten.

The tension in each leg of a two-leg sling = (load weight / 2) / sin(angle from horizontal); tension rises as the angle decreases.

A bowline creates a fixed loop that will not slip under load and is easily untied; a clove hitch is used for temporary attachment and can slip if the load rotates.

A timber hitch tightens under load and is used for dragging or hoisting logs and pipe; it requires several wraps around the load to grip.

Steel weight estimate: weight (lb) = volume (in^3) x 0.2836 lb/in^3; a 1-inch square bar 12 inches long weighs about 3.4 lb.

Concrete weight estimate: about 150 lb/ft^3 for normal-weight concrete; a 1 ft x 1 ft x 1 ft block weighs roughly 150 lb.

Water weighs 62.4 lb/ft^3; a cubic foot of water is about 62.4 lb, useful for tanks and pipe contents.

Aluminum weighs about 169 lb/ft^3; steel about 490 lb/ft^3; cast iron about 450 lb/ft^3.

The center of gravity of a uniform rectangular solid is at its geometric center; for a composite load, the CG is the weighted average of component CGs.

A load whose CG is not under the hook will tilt until the CG aligns below the hook; the rigger must adjust sling lengths to level the load.

Load weight must include rigging weight, contents, and any attachments; the crane's rated capacity at the working radius must exceed the total.

For a two-leg bridle, each leg's share of the load depends on where the CG sits; the leg nearer the CG carries a greater share.

Hand signals must be given by one designated signalperson; the operator takes signals only from that person except for a stop signal, which anyone may give.

Raise load: arm extended horizontally, forearm up, index finger pointing up, hand moved in a small circle.

Lower load: arm extended horizontally, forearm down, index finger pointing down, hand moved in a small circle.

Stop: arm extended horizontally, palm down, moved back and forth horizontally.

Emergency stop: both arms extended horizontally, palms down, moved rapidly back and forth.

Dog everything (hold): both fists held at waist level, forearms vertical, in front of the body.

Swing: arm extended horizontally, point in the direction of swing with the index finger.

Before any lift: verify the load is balanced, tag lines are attached if needed, the path is clear, and the load is lifted a few inches to check rigging and stability.

Hoist (raise): with forearm vertical and index finger pointing up, move hand in a small horizontal circle.

Lower: with arm extended downward and index finger pointing down, move hand in a small horizontal circle.

Boom up: arm extended horizontally, fingers closed, thumb pointing up, and move hand upward.

Boom down: arm extended horizontally, fingers closed, thumb pointing down, and move hand downward.

Move slowly: use one hand to give any motion signal and place the other hand motionless in front of the hand giving the signal.

Travel: extend arm forward, hand open and slightly raised, and make pushing motion in the direction of travel.

Stop: extend arm horizontally, palm down, and move arm back and forth horizontally.

The operator must stop when the signalperson is out of sight or the signal is unclear; the lift does not resume until communication is restored.

Sling angle factor = sin(angle from horizontal); tension per leg = load / (number of legs x sin(angle)).

A sling at 60 degrees from horizontal carries 1.155 times its share of the load compared with a vertical leg; at 30 degrees it carries 2.0 times.

Never use a sling at less than 30 degrees from horizontal unless the sling and hardware are rated for the resulting tension.

A basket hitch with vertical legs has about twice the capacity of a single vertical leg; a choker hitch has about 75-80%.

A double-wrap choker or basket increases grip on the load and reduces the chance of slippage.

The D/d ratio (sling body diameter to load diameter) affects basket capacity; a small D/d ratio reduces the effective capacity.

A bridle hitch with unequal leg lengths shifts load to the shorter leg; equalize leg lengths or account for the imbalance.

Tag lines control rotation and swing but must never be used to pull a load beyond the rated radius of the crane.

Inspect slings and hardware before each shift and after any shock load, and remove damaged gear from service immediately.

The load must be lifted a few inches and held while the rigger checks for load shift, sling slippage, and hardware seating before the main lift.

Keep personnel out from under suspended loads and outside the swing radius; the crane's swing radius must be barricaded.

The crane's load chart capacity at the working radius must exceed the total load, including rigging and any dynamic effects.

Wind, side loading, and off-level ground reduce effective capacity; the lift director must reassess if conditions change.

Tag lines should be used on loads that could rotate or swing, and the tag line handler must stay clear of the load path.

A load must never be dragged sideways with a crane; side loading can damage the boom and cause collapse.

Hooks must have a functioning latch and must not be cracked, bent, or worn more than 10% in the throat opening or 15% in the saddle.

Shackle pins must be fully engaged; never replace a shackle pin with a bolt of unknown grade.

Turnbuckles and chain hoists used for overhead lifting must be marked with a rated capacity and proof-tested.

Wire rope slings must have a legible tag showing capacity, and the tag must not be removed or covered.

Synthetic slings must be protected from sharp edges, heat, and chemicals; covers or edge protectors extend service life.

Chain slings must be inspected for stretch, gouges, cracks, and worn links; a link worn more than 15% of its thickness is removed.

Rigging hardware must be proof-loaded and marked; unmarked hardware is not acceptable for overhead lifting.

Weight = volume x density; for steel use 0.2836 lb/in^3 or 490 lb/ft^3.

Pipe weight estimate: weight per foot = (outside diameter - wall thickness) x wall thickness x 10.68 for steel pipe in inches.

A 55-gallon drum of water weighs about 458 lb; the drum itself adds roughly 20-40 lb.

A cubic yard of concrete weighs about 4,050 lb (150 lb/ft^3 x 27 ft^3).

The CG of a load must be directly below the hook; if it is offset, the load tilts and the sling legs carry unequal tension.

For a load with an offset CG, the tension in each sling leg is proportional to its horizontal distance from the CG.

Weigh or calculate the load; never estimate by eye when the load is near the crane's rated capacity.

Only one designated signalperson gives signals; the operator takes a stop signal from anyone.

Hand signals must be clear and given from a position in full view of the operator.

Radio communication must use a dedicated channel and clear, standardized language; the signalperson identifies the load and the action.

If the signalperson is out of sight, the operator stops and waits for communication to be restored.

Emergency stop: both arms extended horizontally, palms down, moved rapidly back and forth.

The signalperson must be qualified and must understand the crane's load chart and the lift plan.

Voice signals are permitted only when hand signals are impractical and the operator and signalperson agree on the meaning.