NCCCO Digger Derrick flashcards

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

Rated capacity

The maximum load a digger derrick may lift at a given radius and configuration, equal to the lowest of structural, stability, winch, and auger limits shown on the load chart.

Load radius

The horizontal distance from the center of rotation to the center of the load, measured with the boom at its actual angle and extension, not along the boom.

Load moment indicator

A device that senses boom angle, length, and load to compute the load moment and warn or stop the operator before the rated capacity is exceeded.

Anti-two-block device

A switch that stops hoisting when the hook block approaches the boom tip too closely, preventing rope damage and load loss from two-blocking.

Wire rope removal criteria

Common criteria include six or more randomly distributed broken wires in one lay, three in one strand in one lay, or a ten percent diameter reduction.

Outrigger float

The pad or float attached to the outrigger beam that spreads the outrigger force over a larger ground area to reduce soil bearing pressure.

Full outrigger spread

Fully extending all outrigger beams and setting pads on stable, level ground, which is required for the highest capacity chart entries.

Carrier leveling

Using the outriggers to bring the carrier bubble level before lifting, so the load chart and stability calculations remain valid.

Soil bearing capacity

The allowable pressure the ground can support under an outrigger pad, used to size pads so the machine does not settle or tip.

Utility tolerance zone

The band on each side of a marked underground utility, commonly 18 to 24 inches, within which excavation must be by hand or vacuum.

Minimum approach distance

The closest distance any part of the machine, load, or personnel may come to an energized line, set by voltage and employer rules.

Equipotential zone

A work area where all conductive objects are bonded together so they remain at the same potential, protecting workers near energized lines.

Pole grabber

A hydraulically actuated attachment on the boom that clamps and holds a pole during lifting and setting, and whose weight reduces allowable load.

Tag line

A rope attached to the load and controlled by a ground worker to restrain rotation and swing without the worker touching the load.

Digger motor

The hydraulic motor that rotates the auger, producing high torque and a reaction force that the boom and turntable must resist.

Auger torque reaction

The counter-rotating force on the boom and turntable when the auger turns, which can swing the boom if not controlled.

Pilot bit

The center point on the auger that guides the bit into the soil and helps start the hole at the marked location.

Signal person

The single designated crew member who directs the operator with hand signals or radio, and whose stop signal must always be obeyed.

Emergency stop signal

A prearranged signal that any crew member may give to halt all machine motion immediately, regardless of who is directing the lift.

Pre-lift meeting

A briefing covering load weight, radius, rigging, signals, tag line assignments, exclusion zones, and emergency procedures before the lift begins.

Swing radius

The area swept by the boom, load, and counterweight during rotation, which must be barricaded and kept clear of personnel.

Side loading

Pulling or dragging a load sideways with the boom or auger, which is outside the load chart and can buckle the boom.

Dynamic load

Additional force from sudden starts, stops, or load release that can exceed the static rated capacity and overload the boom or rope.

Pre-operation inspection

The documented check of wire rope, hooks, hydraulics, safety devices, auger, and outriggers performed before each shift and after incidents.

Boom deflection

The downward bending of the boom under load, which increases actual radius and reduces capacity compared with the unloaded geometry.

Winch line pull

The maximum pulling force of the winch, rated at the bare drum and reduced as rope layers build up on the drum.

Pole setting depth

The depth the pole butt is buried, commonly about ten percent of pole length plus two feet, confirmed before backfill.

Backfill compaction

Compacting soil around a set pole to restore lateral support and uplift resistance, preventing the pole from leaning or pulling out.

De-energized verification

Confirmation by the utility that a line is de-energized, followed by visible grounding, before work within the minimum approach distance.

Ground gradient hazard

Voltage differences across the soil near a downed or contacted line that can injure workers through step and touch potential.

Hand signal

A standard arm and hand motion used by the signal person to direct boom, swing, hoist, and stop functions when radio is unavailable.

Load chart configuration

The specific boom length, outrigger spread, and counterweight setup that a load chart entry applies to, which must match the machine.