NCCER Tower Crane flashcards
NCCER Tower Crane · Build recall with a focused review session.
33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Load moment
- The product of load weight and working radius. The load moment limiter compares this value to the crane's rated moment and stops hoisting or trolleying out when exceeded.
- Rated capacity
- The maximum load a crane may lift at a specific radius, jib length, counterweight, and reeving, as published in the manufacturer's load chart.
- Load moment limiter
- A safety device that measures load and radius, computes the load moment, and prevents operation beyond the rated moment by limiting hoist and trolley-out motions.
- Free-standing height
- The maximum mast height a tower crane may reach without wall ties or guy wires, specified by the manufacturer and limited by mast strength and stability.
- Climbing frame
- A structural frame that supports the crane during climbing while a new mast section is inserted, then transfers load back to the mast.
- Wall tie
- A structural connection between the crane mast and a building or independent support that restrains the mast and allows height beyond free-standing limits.
- Counter-jib
- The rearward jib that carries counterweights to balance the load moment of the forward jib and load, reducing mast bending.
- Slew ring
- The large bearing that connects the rotating upper works to the mast and allows the crane to swing through 360 degrees under load.
- Anti-collision system
- A system using zone limits and crane-to-crane communication to prevent physical contact or load interference between overlapping tower cranes on a site.
- Weathervaning
- The practice of leaving the jib free to rotate with the wind when the crane is out of service, reducing wind load on the mast.
- Anemometer
- A wind-speed measuring device mounted on the crane, typically at the jib or mast top, used to enforce in-service and out-of-service wind limits.
- Rail stops
- End-of-runway devices that physically stop a rail-mounted crane from traveling off the rails, used with buffers and anti-rail-climbing devices.
- Ground bearing pressure
- The pressure exerted by the crane's foundation on the soil, calculated from total weight and effective area and checked against the geotechnical report.
- Table T clearance
- OSHA minimum approach distances to energized power lines, starting at 10 ft for lines up to 50 kV and increasing with voltage.
- Erection director
- The qualified person responsible for directing erection, climbing, and dismantling operations according to the approved engineered plan.
- Verticality tolerance
- The maximum allowable out-of-plumb deviation of the mast, typically expressed as a fraction of height (e.g., 1/500) and checked after each climb.
- Dismantling sequence
- The reverse of erection: remove counterweights and jib first, then reduce mast sections, maintaining stability at every stage per the engineered plan.
- Erection wind limit
- The maximum wind speed, usually lower than the in-service limit, at which erection, climbing, or dismantling may proceed safely.
- Sling angle tension
- Leg tension equals load divided by the number of legs times the sine of the angle from horizontal; shallower angles increase tension sharply.
- Choker hitch
- A sling configuration that wraps around the load and passes through its own eye, reducing capacity to roughly 75–80 percent of the vertical rating.
- Basket hitch
- A sling configuration where both eyes are attached to the hook and the sling cradles the load, often rated up to twice the single-leg vertical capacity.
- Working load limit
- The maximum load a rigging component is designed to support in a specific configuration, marked on shackles, hooks, and slings.
- Designated signal person
- The single qualified individual responsible for directing the operator by hand signals or radio during a lift.
- Emergency stop signal
- A hand signal or verbal command that any person may give to halt crane motion immediately, regardless of who is the designated signal person.
- Tag line
- A rope attached to a suspended load and controlled from the ground to restrain rotation and swing during hoisting and slewing.
- Shock loading
- Sudden application or release of load, such as snatching or rapid stopping, which can produce forces far above the static load.
- Side loading
- A horizontal force applied to the jib or mast, such as dragging a load, that the crane is not designed to resist and that can cause buckling.
- Multi-crane lift
- A lift using two or more cranes that requires a written plan, one signal person, and load sharing that keeps each crane within capacity.
- Runway rail
- The track on which a rail-mounted tower crane travels, requiring level alignment, anchoring, and end stops per manufacturer specifications.
- Slewing radius
- The horizontal distance from the slewing center to the outermost point of the rotating structure, defining the swing hazard zone to be barricaded.
- Pre-shift inspection
- A documented check of wire rope, hooks, brakes, limit switches, and anemometer performed before each shift by a qualified person.
- Reeving
- The number and arrangement of hoist rope parts between drum and hook block, which affects lifting capacity and hoist speed.
- Foundation curing strength
- The minimum concrete compressive strength, specified by the manufacturer, that must be reached before erection loads are applied.