NCCCO Rigger Level II key terms

A manufacturer-supplied table or graph showing the maximum capacity a crane can handle at specific boom lengths, radii, and configurations. It also lists limits based on structural strength, stability, and other operating factors.

The force a crane or lift spreads over the ground beneath outriggers, tracks, or tires, usually stated in pounds per square foot. It determines whether the surface can support the load without settling or failing.

The single point where a load's weight balances in all directions. Rigging must be arranged so the hook is directly above this point, otherwise the load will tilt when raised.

The horizontal distance from the crane's rotation center to the center of the load with the boom in its working position. Capacity drops as radius grows because the load creates more overturning force.

A written document identifying the load, its weight and center of gravity, the rigging to be used, crane configuration, ground conditions, hazards, and the step-by-step sequence of the lift.

A lift that exceeds a set percentage of the crane's rated capacity, uses more than one crane, puts personnel under the load, or involves unusual hazards. It normally requires a detailed engineered plan and extra review.

The circular area swept by the crane's counterweight, boom, and load as the upper structure rotates. Barriers and exclusion zones keep workers out of this hazard area during operation.

The closest a crane, boom, load, or rigging may come to an energized power line, set by line voltage and regulation. A spotter, and sometimes de-energizing, is required when working near lines.

The exposed surface area of a load that catches wind. Large, light loads can be pushed or swung even in modest breeze, so the lift plan limits wind speed based on sail area.

The angle measured between a sling leg and the horizontal underside of the load. As this angle gets flatter, tension in the leg rises sharply, so capacity is reduced.

The force carried by each sling leg, which grows as the leg moves away from vertical. It equals the load weight divided by the number of legs, adjusted for the angle.

A sling wrapped around the load and passed through one of its own eyes so it tightens as the load lifts. Choking reduces the sling's capacity compared with a straight vertical hitch.

A sling passed under the load with both eyes on the hook, cradling the load from beneath. With legs vertical it can carry about twice the single-leg rating, but only if the load stays balanced.

Two or more sling legs joined at a common point above the load and attached to separate lifting points. Load distribution depends on the geometry and the position of the center of gravity.

A U-shaped connector with a pin or bolt used to join slings to lifting points. Its working load limit is marked on the body, and the pin must be fully seated before loading.

A large forged ring at the top of a multi-leg sling assembly that gathers all the legs and connects to the crane hook. It is sized for the total capacity of the assembly.

A lifting device that holds sling legs apart so they stay vertical or nearly vertical, reducing compression on the load. It works mainly in bending and suits long or flexible loads.

A rigid beam with attachment points that carries the load in bending and transfers force through its own structure. Unlike a spreader, it is designed to take the forces produced by angled sling legs.

The ratio of the diameter of the bend a wire rope sling wraps around to the rope diameter. A small ratio lowers efficiency and can damage the rope, so minimum ratios are specified.

The maximum load a rigging component is rated to lift in a specific configuration. It is marked on the component and must never be exceeded, even briefly.

The ratio between a component's breaking strength and its working load limit. It provides a margin for wear, dynamic forces, and uncertainty in how the load is applied.

Padding, softeners, or corner protectors placed between a sling and sharp or abrasive load edges to prevent cutting, crushing, or wear of the sling material.

A visual and functional check of rigging performed by the user before each shift or use, looking for damage, missing tags, and proper operation. It does not replace periodic inspection.

A more thorough inspection done at set intervals by a qualified person, with frequency based on use, environment, and manufacturer recommendations. Results are documented and compared against removal criteria.

Specific defects or wear limits that require a rigging component to be taken out of service, such as broken wires, cracks, excessive hook opening, or a missing identification tag.

A wire rope failure in which outer strands separate and bulge away from the core, usually caused by shock loading or reverse bending. It is a removal criterion because the rope loses strength.

The distance measured across the inside of a hook. Stretching beyond a set percentage of the original dimension indicates overload or deformation and requires the hook be removed from service.

A test that applies a specified load greater than the working load limit but below breaking strength to verify a component's integrity. It is not a destructive test.

A lift using two cranes to raise one load that is too heavy or too long for a single crane. It requires a written plan, defined load sharing, and one person directing both operators.

The portion of a tandem load's weight carried by each crane, which depends on the center of gravity position and the rigging geometry. It must be calculated rather than assumed to be equal.

A lift in which the load is moved horizontally by traveling or booming while it hangs, often used to place loads in tight spaces. The load must stay under control throughout.

A dangerous condition where the load block contacts the boom tip or sheave, which can snap the wire rope. Limit switches and correct boom angle help prevent it.

A sudden application of force caused by jerking, rapid stopping, or a load dropping onto a sling. It can multiply the effective load far beyond the static weight.

Pulling a boom or sling sideways away from its designed direction of load. It can overload structural components and is prohibited unless the manufacturer specifically permits it.

A rope attached to a load and controlled by a worker on the ground to keep the load from spinning or swinging. It must never be wrapped around a hand or body.

A set of agreed gestures a signalperson uses to direct crane movement when voice communication is impractical. Everyone on the crew must use and recognize the same signal set.

A qualified person assigned to direct the crane operator, positioned where both the operator and the load can be seen. Only one person should give signals at a time.

A signal that halts crane movement immediately. Any worker who sees danger may give it, and the operator must obey no matter who gave it.

A lift in which the operator cannot see the load or the landing area, requiring a signalperson or radio communication to guide the movement step by step.