NCCER Mobile Crane flashcards

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

Ground bearing pressure

Total weight of crane plus load divided by the contact area of pads or tracks. Adding larger floats or cribbing spreads the load and lowers pressure per unit area.

Outrigger beam extension

Outriggers must be extended and pinned per the manufacturer's chart. Partially extended beams have separate, lower capacity ratings and may be prohibited for lifting.

Crane level tolerance

The crane must be level within the manufacturer's stated tolerance, often one degree or less. Out-of-level setup invalidates chart capacities and causes side loading of the boom.

Pre-shift inspection

Operator check before each shift covering wire rope, hook and latch, brakes, sheaves, drums, pins, hoses, outriggers, and safety devices. Deficiencies are corrected before lifting.

Swing radius barricade

A physical barrier around the rotating superstructure and counterweight tail swing. Only necessary personnel may enter, and only when the crane is not swinging.

Shutdown and securing

Land the load, stow the boom and hook per the manufacturer, set brakes and outrigger locks, and secure the machine against wind and unauthorized operation.

Bridle sling tension

For a symmetric two-leg lift, tension per leg equals half the load divided by the sine of the angle from horizontal. Flatter angles greatly increase leg tension.

Sling angle factor

Multiply the load by one divided by the sine of the sling angle from horizontal to find the tension in each leg of a two-leg lift.

Choker hitch capacity

A choker reduces sling capacity compared with a vertical hitch, commonly to about 75 to 80 percent, depending on the sling type and manufacturer's rating.

Center of gravity control

The hook must be directly above the load's center of gravity. Off-center attachment tilts the load, shifts tension between legs, and can cause uncontrolled rotation.

Shock loading

Sudden application or release of force, such as jerking a load off the ground, multiplies stress beyond the static rating and can fail slings or the crane.

Sling removal criteria

Remove slings with broken wires, cuts, burns, ultraviolet or chemical damage, missing identification tags, or distorted hooks and hardware from service.

Net capacity formula

Gross capacity from the load chart minus the weight of everything below the boom tip: hook block, slings, shackles, jib, and stowed attachments.

Load radius measurement

Horizontal distance from the crane's center of rotation to the load's center of gravity. It is not measured to the boom tip or the near edge of the load.

Boom length effect

At the same radius, a longer boom generally reduces capacity because of added boom weight and deflection. Always use the chart row matching the actual boom length.

Area of operation

The chart section defining the setup: on outriggers, on tires, pick-and-carry, or travel. Capacities differ by area and by quadrant of swing.

Rated capacity limiter

A device that warns and stops crane functions when the load approaches the rated capacity. It assists the operator but does not replace the printed load chart.

Chart interpolation

Estimating capacity between listed radii or boom lengths is permitted only when the manufacturer's instructions allow it. Otherwise use the next lower listed value.

Designated signal person

A qualified person who directs the operator when the load or landing area is not visible. Only one person gives signals at a time.

Emergency stop signal

Any rapid hand or arm movement across the body, or any other emergency signal, requires the operator to stop immediately, regardless of who gives it.

Hand signal set

Standardized signals for raise and lower load, raise and lower boom, swing, stop, extend and retract boom, and travel. Operator and signaler must know the same set.

Radio communication discipline

Radios dedicated to the lift with clear, distinct voice signals. If communication is lost or garbled, the operator stops until contact is restored.

Signal person positioning

The signal person must see the load, rigging, and landing area, and maintain line of sight with the operator or use a relay signaler.

Travel signals

Travel directions are given from the direction of travel or by a designated flagger. The operator follows only the designated signal person.

Power line clearance

Minimum 10 ft for lines up to 50 kV, plus 0.4 in per kV above 50 kV, unless the line is de-energized and grounded or a documented alternative is used.

Critical lift plan

A written plan for lifts near capacity, multi-crane lifts, lifts over occupied areas, or personnel lifts, including rigging, load weight, and contingency steps.

Wind stop criteria

Stop lifting when wind exceeds the manufacturer's limit or when the load's sail area prevents control. Lightning, ice, and poor visibility also stop work.

Ground condition assessment

Evaluate soil bearing, voids, uncompacted fill, and slope before setup. Use mats or cribbing sized to the outrigger load and verify underground utilities.

Two-blocking hazard

The hook block contacts the boom tip, tensioning the rope and potentially dropping the load or damaging the boom. Anti-two-block devices must remain functional.

OSHA crane standards

29 CFR 1926 Subpart CC covers cranes and derricks in construction. General industry crawler cranes fall under 1910.180, and overhead cranes under 1910.179.

Personnel lifting platform

Lifting people requires a specifically designed platform, manufacturer's approval, a pre-lift plan, and fall protection. Riding the hook or load is prohibited.

Qualified operator requirement

Only trained and qualified operators, riggers, and signal persons may perform those tasks. Employers must verify qualifications and keep records.