NM Crane Operator flashcards

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

Load radius

Horizontal distance from the crane's center of rotation to the load's center of gravity. Capacity decreases as radius increases, so radius must be measured to the load, not the boom tip.

Net capacity

Gross chart capacity minus the weight of all lifting attachments below the boom tip, including hook block, slings, spreader bar, and jib. The result must exceed the load plus rigging.

Load moment

The product of load weight and load radius. Load moment indicators compare this value against the crane's rated moment to warn of overload or tipping conditions.

Sling angle factor

Multiplier equal to one divided by the sine of the sling angle from horizontal. At 30 degrees the factor is 2.0; at 60 degrees it is about 1.155.

Two-leg bridle tension

For a symmetric two-leg bridle, each leg carries half the load divided by the sine of the angle from horizontal. Flatter angles sharply increase leg tension.

Four-leg bridle assumption

Because load sharing among four legs is never equal, capacity is typically calculated as if only two legs carry the load. Unequal leg lengths worsen the imbalance.

Ground bearing pressure

Total weight of crane, counterweight, load, and rigging divided by the effective bearing area under the outrigger floats or mats. Mats reduce pressure by increasing area.

Outrigger float pressure

Concentrated pressure under a single outrigger float can reach several hundred psi. A mat spreads the load over a larger area and lowers pressure proportionally.

Level tolerance

Manufacturers commonly require the crane to be level within about one percent. Out-of-level setup reduces capacity and causes the load to swing uncontrolled.

Void under outrigger

A buried tank, vault, utility, or void beneath a float creates a tip-over hazard even when the surface looks solid. Verify subsurface conditions before setup.

Swing radius barricade

The area swept by the counterweight and boom during rotation must be barricaded to keep personnel clear. Tail swing extends beyond the crane's footprint.

Designated signal person

Only one signal person directs the lift at a time. The operator obeys that person but must stop for a stop signal from anyone on site.

Lost signal condition

If the signal person is out of view, the radio fails, or the signal is unclear, the operator stops the lift until communication is restored.

Anti-two-block device

A safety device that stops hoisting before the hook block contacts the boom tip. It must be tested before each shift and never bypassed.

Load moment indicator

An instrument that computes load moment from boom angle, length, and load and warns or stops operation before the rated moment is exceeded.

Wire rope removal criteria

Broken wires, diameter reduction, corrosion, kinking, crushing, or core protrusion beyond manufacturer or OSHA limits require removal of the rope from service.

Synthetic sling rejection

Web slings are removed for cuts, snags, burns, UV damage, or missing tags. They must also not be used above the manufacturer's temperature limit.

Pre-shift inspection

Daily check of fluids, tires, outriggers, boom, wire rope, hook block, and safety devices before operation. A failed safety device takes the crane out of service.

Boom length measurement

Boom length is the pin-to-pin distance along the boom centerline. Jib length is measured separately and adds to tip radius rather than to boom length.

Boom angle effect

Boom angle is measured from horizontal. Lowering the angle increases radius and reduces capacity at the same boom length.

Counterweight tradeoff

Counterweight reduces forward tipping moment but increases ground bearing pressure and tail swing envelope. It is not part of the lifted load.

Outrigger spread chart

Fully extended and mid-extended outrigger positions have different load charts. Operating at partial extension requires the manufacturer's intermediate chart.

Rough-terrain travel chart

Traveling with a load requires the manufacturer's travel chart, which is separate from the lifting chart and usually allows less capacity.

Power line assumption

All overhead lines are treated as energized until the utility confirms de-energization in writing. Unknown voltage is treated as the highest category.

Minimum approach distance

Required clearance from energized lines, set by voltage in OSHA Table T. For lines under 50 kV the minimum is typically 10 feet.

Crane contacts line

The operator stays in the cab, warns others away, and calls the utility. No one touches the crane or load until the line is de-energized.

Leaving energized crane

If the operator must exit, jump clear and shuffle away with feet together, never touching the crane and ground at the same time.

OSHA Subpart CC

29 CFR 1926 Subpart CC governs cranes and derricks in construction, covering operator qualification, inspection, signaling, and power line clearance.

Operator certification

Construction crane operators must be certified by an accredited certifying body or qualified under the applicable standard before operating.

Competent person inspection

The employer must ensure equipment is inspected by a competent person, in addition to the operator's pre-shift inspection each shift.

Critical lift plan

A written plan required for complex lifts, multiple cranes, or lifts near power lines or personnel, addressing capacity, rigging, and contingencies.

New Mexico adoption

New Mexico's occupational safety framework adopts federal OSHA standards, so 1926 Subpart CC minimums apply to construction crane work in the state.