NM Crane Operator key terms

The angle between the centerline of the boom and the horizontal, measured in degrees. It is one of the inputs used to read capacity from a load chart and to calculate working radius.

A manufacturer-issued table or graph showing the maximum allowable load for a crane at specific configurations such as boom length, boom angle, radius, and outrigger setup. It governs every lift.

The horizontal distance from the crane's center of rotation to the vertical centerline of the load, measured with the boom under load. Capacity decreases as radius increases.

The total lifting value taken directly from the load chart for a given configuration, before any deductions. It is the starting number from which all lifting-gear and attachment weights are subtracted.

The actual load a crane may lift after subtracting the weight of rigging, slings, shackles, spreader beams, and any other attachments from the gross capacity shown on the load chart.

All weights that must be subtracted from gross capacity to determine what payload can be lifted, including hook block, slings, shackles, spreader beams, and attached devices such as personnel platforms.

The extended length of the crane's boom from boom foot to boom tip, often built from telescoping sections. It is a required input when selecting the correct row or curve on a load chart.

The vertical axis about which the crane's upper structure swings. All working radii are measured from this point, so its location must be established on the ground before lifting.

Heavy removable plates mounted at the rear of the rotating upper structure that offset load moment and help keep the crane stable. Its value is fixed in the load chart and must not be altered.

The turning effect produced by the load and boom, calculated as load times radius. Crane capacity is limited by the maximum load moment the structure and stability can safely resist.

The crane's resistance to tipping about its outriggers, crawlers, or wheels under the combined weight of load, boom, and counterweight. It is the controlling limit for most lifts at long radius.

The maximum load the crane's boom, jib, pins, and other components can carry without yielding or failing. It may control capacity instead of stability at short radius or high boom angles.

Extendable hydraulic leg with a float pad that widens the crane's support base and levels the machine. Outriggers must be fully extended and set on firm, prepared ground before lifting.

A rigid plate placed under an outrigger or crawler track to spread load over a larger ground area and reduce bearing pressure. Proper sizing depends on soil strength and outrigger load.

The force per unit area that the crane's outriggers or tracks impose on the soil beneath. It must not exceed the soil's capacity, or the crane may settle, shift, or tip.

Layered timbers, mats, or steel plates placed under outriggers or tracks to spread load and bridge soft spots. Cribbing must be level, sized for the load, and free of gaps.

An underground cavity such as a septic tank, utility vault, basement, or culvert beneath a crane's support point. Unidentified voids can collapse under outrigger load and cause a tip-over.

A pre-lift walk-through identifying hazards such as slopes, soft soil, voids, overhead power lines, obstructions, and access routes. Findings drive crane positioning and lift planning decisions.

A flexible assembly of wire rope, chain, or synthetic webbing used to connect the load to the crane hook. Slings must be rated, inspected, and protected from sharp edges.

The angle between a sling leg and the horizontal, which determines how much tension the leg carries. Shallower angles increase tension sharply and reduce the assembly's usable capacity.

A multiplier applied to half the load to find tension in each sling leg for a two-leg bridle. It grows as the sling angle becomes shallower and is often expressed as length over height.

The pulling force carried by each sling leg or rigging component. It must be compared to the component's rated capacity, never to the weight of the load alone.

The maximum load a sling, shackle, hook, or other component is designed and marked to carry in a stated configuration. It must equal or exceed the tension or load applied.

The maximum mass or force a rigging component is authorized to support in a particular service. It is typically marked on the item and is reduced for non-vertical sling configurations.

A U-shaped metal connector closed with a pin or bolt, used to join slings to hooks, eyes, or lifting lugs. The pin must be fully seated and the shackle rated for the load.

A two-leg sling arrangement in which each leg attaches to a separate lifting point on the load and both legs meet at the hook. Leg tension depends on the included angle between legs.

A spring-loaded device that closes the throat of a crane or rigging hook to prevent slings and lines from slipping out. A missing or damaged latch removes the hook from service.

A sensing system that warns the operator or stops hoisting and booming down before the hook block contacts the boom tip. It prevents rope damage and load loss from two-blocking.

An onboard computer that displays boom angle, radius, load, and percent of rated capacity, and warns or stops operations when limits are approached. It supplements but does not replace the load chart.

The documented check of a crane before each shift or use, covering fluids, leaks, wire rope, hooks, brakes, limit devices, and safety decals. Defects found must be corrected before operation.

A more thorough examination performed at intervals set by the manufacturer or regulation, often annually, by a qualified person. Records of the inspection and any repairs must be retained.

The systematic check of running and standing rope for broken wires, kinks, birdcaging, corrosion, and diameter loss. Removal criteria are based on the number and distribution of broken wires.

Examination of slings, shackles, hooks, and hardware for wear, cracks, cuts, stretching, or missing tags before each use. Damaged gear is tagged out and removed from service immediately.

A prescribed set of arm and hand movements used by a signal person to direct crane motion when voice or radio communication is unavailable. Only one person should signal at a time.

A qualified individual who directs the operator using standard signals and is responsible for stopping the lift when conditions become unsafe. The operator must obey a stop signal from anyone.

A rope attached to a load to control rotation and swing during hoisting without the worker touching the load. Tag lines keep personnel clear of the load's path and pinch points.

Rotation of the crane's upper structure about its center of rotation. Swing must be smooth and slow with the load controlled, because sudden stops cause load swing and side loading.

Any force applied to the boom perpendicular to its designed direction of loading, such as dragging a load or swinging too fast. It can buckle the boom and is prohibited unless approved by the manufacturer.

An energized overhead or buried conductor that poses an electrocution hazard to cranes and rigging. Minimum approach distances and a designated spotter are required when working near one.

The closest distance any part of the crane, load, or rigging may come to an energized power line, set by voltage and regulation. It applies even when the operator believes the line is de-energized.

A dedicated person who watches the clearance between the crane and power lines and warns the operator. The spotter must be positioned to see the hazard and have a clear way to signal stop.

A voltage difference across the ground surface near a downed or contacted conductor that can shock a person whose feet span different voltage zones. Shuffle or hop away, never run.

A person who, by possession of a recognized degree, certificate, or professional standing, or by extensive knowledge and experience, can successfully solve or resolve problems relating to the subject matter.

A person capable of identifying existing and predictable hazards and who has authority to take prompt corrective action. Site and ground-condition decisions often require a competent person.

A written document that identifies the load, crane configuration, capacity, rigging, hazards, and responsible persons for a lift. Critical lifts and work near power lines require one.

A lift that exceeds a set percentage of the crane's rated capacity, involves personnel, or presents unusual risk, requiring a formal plan and often engineering review. Thresholds come from the employer or site rules.

Documented proof that a crane operator has been evaluated and meets the requirements of the applicable standard for the crane type being operated. It must be available for inspection on site.