Basic Rigging (RB) flashcards

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

Qualified rigger

A person who, by possession of a recognized degree, certificate, or professional standing, or by extensive knowledge, training, and experience, has demonstrated the ability to rig loads safely.

Design factor for slings

The ratio of a sling's breaking strength to its rated capacity; most slings use a design factor of 5, while chain slings used overhead use a factor of 4.

Wire rope removal criteria

A wire rope sling is removed from service when it has 10 or more randomly distributed broken wires in one lay, or 5 broken wires in one strand of one lay.

Swing radius barricade

The area within the crane's swing radius must be barricaded to keep personnel out; the barricade protects workers from being struck by the rotating superstructure or counterweight.

Shackle pin seating

A screw pin shackle must have its pin fully seated with no gap before loading; a partially engaged pin can strip threads and release the load.

Eye bolt angular derating

An eye bolt loaded at 45 degrees from its axis retains about 70% of rated capacity; at 90 degrees it retains only about 30%.

Wire rope clip orientation

The U-bolt of a wire rope clip goes over the dead end of the rope, and the saddle goes over the live end; the correct number of clips and spacing depend on rope diameter.

Master link capacity

The master link of a multi-leg sling assembly must be rated at least equal to the sum of the leg capacities at the hitch angle used.

Vertical hitch

A single sling leg hanging straight down from the hook to the load; the leg carries the full load and the capacity equals the sling's vertical rating.

Choke hitch

The sling passes around the load and back through its own eye; capacity is typically 75-80% of the vertical rating because of the choke angle.

Basket hitch

The sling passes under the load with both eyes on the hook; with vertical legs the capacity is about twice the single-leg vertical rating.

Sling angle factor

The multiplier sin(angle from horizontal) used to compute leg tension; tension per leg equals load divided by (number of legs times the angle factor).

Two-leg sling at 60 degrees

Total capacity equals 2 times the leg rating times sin(60), or 1.732 times the leg rating; each leg carries load divided by 1.732.

Two-leg sling at 30 degrees

Total capacity equals 2 times the leg rating times sin(30), or 1.0 times the leg rating; flattening the slings sharply reduces capacity.

Bowline knot

A knot that forms a fixed loop which will not slip under load and is easily untied; used to attach a line to a load or to form an eye.

Timber hitch

A hitch that tightens under load and is used for dragging or hoisting logs and pipe; it requires several wraps around the load to grip.

Steel weight per cubic inch

Steel weighs about 0.2836 lb per cubic inch, or 490 lb per cubic foot; a 1-inch square bar 12 inches long weighs about 3.4 lb.

Concrete weight per cubic foot

Normal-weight concrete weighs about 150 lb per cubic foot; a cubic yard weighs about 4,050 lb.

Water weight per cubic foot

Water weighs about 62.4 lb per cubic foot; a 55-gallon drum of water weighs about 458 lb before adding the drum's own weight.

Center of gravity alignment

A suspended load tilts until its center of gravity is directly below the hook; the rigger adjusts sling lengths to level the load and equalize leg tension.

Offset CG leg tension

When the center of gravity is not centered between the legs, the nearer leg carries a greater share of the load; tension is proportional to horizontal distance from the CG.

Total load calculation

The crane's rated capacity at the working radius must exceed the load plus rigging, contents, and attachments; never estimate by eye near capacity.

Designated signalperson

The single person authorized to give hand signals to the operator; the operator takes signals only from that person except for a stop signal, which anyone may give.

Raise load signal

Arm extended horizontally, forearm up, index finger pointing up, and hand moved in a small circle; this tells the operator to hoist the load.

Lower load signal

Arm extended horizontally, forearm down, index finger pointing down, and hand moved in a small circle; this tells the operator to lower the load.

Stop signal

Arm extended horizontally with palm down, moved back and forth horizontally; any person may give this signal to stop the operation.

Emergency stop signal

Both arms extended horizontally with palms down, moved rapidly back and forth; this signal stops all crane motion immediately.

Dog everything signal

Both fists held at waist level with forearms vertical in front of the body; this tells the operator to hold all crane functions.

Move slowly signal

One hand gives any motion signal while the other hand is held motionless in front of it; this tells the operator to perform the motion slowly.

Swing signal

Arm extended horizontally with the index finger pointing in the direction of swing; this tells the operator to rotate the boom in that direction.

Hook latch requirement

Every crane hook must have a functioning latch that closes the throat; a missing or damaged latch allows slings to slip off the hook under slack conditions.

Sling tag legibility

Each sling must carry a legible tag showing its rated capacity; the tag must not be removed or covered, and an unmarked sling is removed from service.