NCCER Mobile Crane key terms

The amount of force a crane's outrigger float or track exerts on each unit of ground area, calculated from total weight including load and counterweight divided across the supporting points.

The pad attached to the bottom of an outrigger jack that spreads the crane's weight over a larger ground area to reduce sinking and tipping risk.

A timber or composite pad placed under outrigger floats or tracks to spread load over a wider area and improve stability on soft or uneven ground.

Adjusting outriggers or suspension so the crane's turntable and bubble level are within the manufacturer's tolerance, keeping the load chart valid and preventing side loading.

A documented walk-around and functional check of the crane before each shift, covering fluids, wire rope, hooks, brakes, limit switches, alarms, and safety devices.

Examination of hoist and boom pendants for broken wires, corrosion, kinks, birdcaging, and diameter reduction against removal criteria set by the manufacturer or standard.

A safety system that detects when the hook block approaches the boom tip too closely and stops hoisting or boom lowering to prevent rope and block damage.

An onboard computer that senses boom angle, length, and pressure to display rated capacity, actual load, and radius, and warns or stops operation when limits are approached.

The maximum load a crane may lift at a given radius, boom length, and configuration under the manufacturer's load chart, before deductions for rigging and attachments.

The total weight of everything suspended from the boom tip, including the load, slings, shackles, hook block, and any lifting attachments.

The weight of the actual payload only, excluding rigging, hook block, and lifting accessories; used to determine what can safely be lifted after deductions.

The weight subtracted from a crane's charted capacity for items such as hook block, slings, spreader bars, and jib that are not part of the bare boom rating.

The horizontal distance from the crane's center of rotation to the center of the suspended load, measured with the boom at the working angle and length.

The angle between the boom centerline and horizontal, used with boom length to determine radius and rated capacity on the load chart.

The manufacturer's table or graph showing rated capacities for specific boom lengths, radii, angles, quadrants, and outrigger configurations, including notes on deductions and restrictions.

A defined sector around the crane, such as over the front, side, or rear, where the load chart assigns different capacities based on structural and stability limits.

A multiplier applied to load weight when slings are not vertical; as the horizontal angle decreases, tension in each leg increases and capacity of the sling assembly drops.

One branch of a multi-leg sling assembly, whose share of the load depends on its angle and geometry relative to the other legs and the load's center of gravity.

The point where a load's weight is balanced in all directions; the hook must be positioned above it to keep the load level and avoid shifting or shock loading.

A U-shaped rigging connector with a pin or bolt, rated for a specific working load limit and used to join slings, hooks, and lifting points.

The maximum load a rigging component or assembly is rated to support under normal service conditions, marked by the manufacturer and reduced for wear or angle.

A rigging arrangement using two or more slings joined at a common point to lift a load, often used to keep the hook centered over an offset center of gravity.

A rope attached to the load and controlled by a worker on the ground to prevent rotation and swinging during lifting and placement.

Managing a suspended load's position, rotation, and momentum using tag lines, controlled hoist and swing movements, and communication with the signal person.

A qualified worker who directs crane movements using standard hand signals, voice, or radio communication and who must be in clear view of the operator.

A uniform gesture defined by consensus standards for directing hoist, lower, swing, boom, and stop movements so operators and signalers share one language.

A hand signal or emergency command that halts all crane motion immediately; anyone on the job site may give it, and the operator must obey it.

An immediate shutdown of crane motion triggered by a signal, limit device, or operator judgment to prevent injury or damage, after which work does not resume until cleared.

Rotation of the crane's upper structure about its vertical axis; uncontrolled swing can cause load swing-out, side loading, and tipping, especially on unlevel ground.

A force applied to the boom or wire rope outside its designed plane, such as dragging a load or swinging with the load off-center, which can collapse the boom.

A sudden increase in force caused by rapid hoisting, sudden stops, or a slack rope snapping taut, which can exceed rated capacity and damage the crane or rigging.

The minimum safe distance the crane, boom, load, and rigging must maintain from energized lines, determined by voltage and required by the site's electrical safety plan.

A marked area around the crane or beneath the load where unauthorized workers may not stand, protecting them from falling objects, swing hazards, and crush points.

A lift that is unusually heavy, high-risk, over personnel, or near capacity and therefore requires a written lift plan, engineered rigging, and additional supervision.

A written document describing the load, rigging, crane configuration, capacities, ground conditions, travel path, signals, and contingencies for a specific lift.

Contact between the hook block and boom tip that can snap wire rope or damage sheaves, prevented by the anti-two-block device and careful hoist operation.

Extending and setting outriggers on firm, level support with floats or mats, fully extended per the manufacturer, before lifting or swinging the boom.

The extended length of the telescopic or lattice boom, which together with boom angle determines radius and the capacity available on the load chart.