Advanced Rigging (RA) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Sling angle factor

A multiplier equal to one divided by the cosine of the sling's angle from horizontal, applied to the load share to find tension in each leg.

Center of gravity

The point where the entire weight of an object is considered concentrated; a load hangs level only when this point lies directly below the hook.

Overturning moment

The product of a horizontal force and its perpendicular height above a tipping point; tipping occurs when it exceeds the restoring moment from the load's weight.

Asymmetric load share

In a two-point pick, each leg carries a share proportional to its distance from the center of gravity, so the leg nearer the center carries more.

Shackle side loading

Loading a shackle at an angle to its pin-to-bowl axis reduces capacity and requires the manufacturer's rating, not the vertical working load limit.

Choker hitch reduction

A choker hitch typically reduces a synthetic web sling's capacity to about eighty percent of its vertical rating, as stated on the sling tag.

Spreader beam function

A below-the-hook device that holds attachment points apart and carries compressive load, preventing horizontal squeeze on the lifted object.

Screw-pin shackle check

Before use, confirm the pin is fully threaded home and secured; a partially engaged or unsecured pin is a removal-from-service condition.

Stop signal authority

Anyone on the site may give a stop signal, and the crane operator must obey it regardless of who the designated signalperson is.

Load moment

The product of the suspended load and the working radius; it must stay within the crane's rated capacity chart for the actual configuration.

Anti-two-block device

A safety device that prevents the hook block from contacting the boom tip; it must be functional before lifting and must never be bypassed.

Tag line purpose

A rope used to control rotation and swing of a suspended load; it is held from outside the fall zone and never wrapped around a worker's body.

Lang lay wire rope

A rope in which strand wires and strands are twisted in the same direction, giving greater abrasion resistance but less resistance to rotation.

Regular lay wire rope

A rope in which strand wires are twisted opposite to the strand direction, providing better resistance to crushing and less tendency to rotate.

Bowline knot efficiency

A bowline can reduce synthetic rope strength by roughly forty to sixty percent, so a proper splice is preferred for load-bearing terminations.

Wire rope clip placement

The U-bolt is placed on the dead end and the saddle on the live end, spaced at about six rope diameters with the first clip near the thimble.

Jack base preparation

A jack must sit plumb on a firm, level pad sized to spread load; an unstable base can let the jack tip or the piston bend.

Cribbing stack stability

Cribbing is stacked with alternating grain and a low height-to-base ratio so the stack stays stable and resists toppling under load.

Roller skidding friction

Rollers reduce the pull force needed to move a load; the required force approximates the load times the coefficient of rolling friction plus grade resistance.

Multiple jack lifting

When lifting with several jacks, raise in small increments and crib or block the load as it rises; never rely on a jack alone to hold it.

Critical lift plan

A documented plan covering load weight and center of gravity, rigging arrangement, crane capacity, ground bearing, and contingency for a dropped load.

Trial lift

Raising the load slightly before the full lift to verify the center of gravity, rigging geometry, and stability of the arrangement.

Shock loading

Sudden stops or rapid slack removal can multiply the static load several times, so lift plans specify slow, controlled movement.

Wind load scaling

Wind force on a suspended load increases with the square of wind speed, so lift plans state a wind limit at which lifting stops.

Red warning thread

A red core thread visible through a cut or worn synthetic web sling indicates damage; the sling is removed from service immediately.

Chain sling stretch

A chain sling is removed from service when links are stretched beyond the manufacturer's limit or worn more than ten percent of the original dimension.

Periodic inspection interval

Rigging in normal service receives a documented periodic inspection at least annually, more often in severe service or after a shock load.

Overload inspection rule

Any rigging that has been overloaded, shock-loaded, or involved in an accident must be inspected before it returns to service.

OSHA sling standard

OSHA 29 CFR 1910.184 sets requirements for slings, including marking, inspection, and removal-from-service criteria for wire rope, chain, and synthetic slings.

Rated capacity marking

Rigging hardware must be marked with its rated capacity; unmarked or illegible gear is removed from service and must not be used.

Power line clearance

Crane and rigging operations near energized lines must maintain the required minimum clearance, using a spotter or proximity alarm where required.

Stop-work authority

Every worker has the authority to stop a lift they believe is unsafe; accident prevention depends on hazard analysis and exclusion zones under loads.