NCCCO Rigger Level II flashcards

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

Steel plate weight per square foot

Steel plate weighs about 40.8 pounds per square foot for each inch of thickness, derived from the 490 pounds per cubic foot density of steel.

Net crane capacity

Rated capacity at the working radius minus the weight of jib, hook block, slings, spreader beams, and all other below-hook devices and attachments.

Critical lift definition

A lift that exceeds 75 percent of the crane's rated capacity, involves more than one crane, or travels over personnel or an occupied structure.

Tandem lift load share

Total load times the distance from the other crane's pick point to the load center of gravity, divided by the distance between the two pick points.

Power line minimum clearance

Minimum approach for rigging near energized lines: 10 feet up to 50 kV, 15 feet for 50 to 200 kV, and 20 feet for 200 to 350 kV.

Outrigger ground bearing pressure

Total weight of crane plus load divided by the effective area of the outrigger float or mat; larger mats reduce the pressure in pounds per square inch.

Rigging weight in capacity check

Weight of all slings, shackles, spreader beams, and below-hook hardware must be added to the load when comparing against crane capacity.

Choker hitch wire rope efficiency

A choker hitch develops about 75 percent of the sling's single-leg vertical rated capacity, and that reduced value is used for all choker calculations.

Sling tension formula

Tension per leg equals the total load divided by the number of load-bearing legs, multiplied by the sling leg length divided by the head height.

Sling angle multipliers

Measured from horizontal, leg tension is 1.155 times its vertical share at 60 degrees, 1.414 times at 45 degrees, and 2.0 times at 30 degrees.

Thirty degree minimum sling angle

Keep sling legs at 30 degrees or more above horizontal; flatter angles greatly increase both leg tension and the horizontal force squeezing the load.

Web sling hitch factors

Synthetic web slings are rated at 100 percent capacity vertical, 80 percent in a choker hitch, and 200 percent in a basket hitch with vertical legs.

Legs sharing a bridle load

Assume only two legs of a three-leg bridle carry the load, and only three legs of a four-leg bridle, because load sharing is never equal.

Spreader beam purpose

It holds slings vertical or near vertical, converting the horizontal sling component into compression in the beam, which must be rated for that load.

Wire rope sling broken wire limit

Remove a wire rope sling from service when 10 randomly distributed broken wires appear in one lay, or 5 broken wires in one strand in one lay.

Chain sling wear limit

Remove chain when link diameter is worn more than 10 percent, links are cracked, bent, or twisted, or the sling has stretched beyond the manufacturer's limit.

Hook throat opening limit

Remove a hook when its throat opening has increased more than 15 percent, wear exceeds 10 percent, or it is bent or twisted more than 10 degrees.

Shackle wear removal

Remove a shackle when the bow or pin is worn more than 10 percent of its original dimension, or shows cracks, distortion, or damaged threads.

Periodic inspection interval

A documented periodic inspection of rigging equipment is required at least annually by a designated person, in addition to a visual check before each use.

Web sling damage removal

Remove web slings with holes, cuts, snags, burns, ultraviolet or chemical damage, broken stitching, knots, or missing or illegible capacity tags.

Sling identification tag

Every sling must carry a legible tag showing rated capacity, material, length, manufacturer, and serial number; slings without one are removed from service.

Trial lift check

Lift the load a few inches and verify the rigging, load balance, brake holding, and crane stability before hoisting to full height.

Shock loading

Sudden starts, stops, or jerks multiply the dynamic force on rigging well above the static weight and can exceed the rated capacity of slings and hardware.

Tag line function

It controls rotation and swinging of a suspended load; use at least one, more for long or high sail-area loads, and never wrap it around a hand.

Vertical hoist line requirement

Hoist lines must stay vertical; pulling or dragging a load sideways side-loads the boom and is allowed only with the manufacturer's approval.

Multi-crane lift coordination

One lift director coordinates the operation, each crane has its own qualified signal person, and load distribution is monitored to stay within the planned share.

Emergency stop signal

Both arms extended horizontally with palms down and moved rapidly side to side; any person on the job site may give this signal.

Hoist hand signal

Arm extended with the forearm vertical, forefinger pointing up, and the hand moved in small horizontal circles to raise the load.

Designated signal person rule

Only one designated, qualified signal person directs the operator at a time, but anyone may give a stop signal in an emergency.

Radio signal protocol

Use a dedicated channel tested before the lift, give clear commands that are acknowledged and repeated, and identify the signal person and crane being directed.

Qualified signal person

Knows the standard hand and voice signals, understands crane operations, and positions with a clear view of the operator and load, relaying signals when needed.