NCCCO Tower Crane cheat sheet

The foundation must be designed for the crane's maximum in-service load case (rated load plus wind) and its out-of-service case (jib free to weathervane under the site's design storm wind); the storm case frequently governs foundation size.

Soil pressure under the base must not exceed the allowable bearing capacity, which is determined by a geotechnical evaluation, not assumed from surface conditions.

Mast verticality is commonly limited to about 1:500 of measured height; base frame and anchor bolt template are set level within roughly 1 mm per metre before the first mast section is placed.

Locate the base outside the zone of influence of any excavation or trench - commonly a line projected at about 45 degrees up from the excavation toe - unless the foundation is engineered for the reduced support.

OSHA 1926.1408 Table A minimum approach distances to energized lines: 10 ft up to 50 kV, 15 ft for 50–200 kV, 20 ft for 200–350 kV, 25 ft for 350–500 kV, 35 ft for 500–750 kV, 45 ft for 750–1000 kV, 50 ft above 1000 kV.

The crane must be able to slew a full 360 degrees with the jib and counter-jib clear of buildings, other cranes, stockpiles, and power lines, including the weathervaning arc in the parked condition.

Check for buried utilities, voids, and old foundations beneath the base; the crane's concentrated loads are transferred through a small footprint and will not bridge a soft spot.

Rail-mounted cranes require the track to be level, drained, and laid to the manufacturer's grade and gauge tolerances, with end stops sized for the crane's travel speed and wind loads.

Assembly and disassembly must be directed by a person meeting OSHA's qualification requirements and performed following the manufacturer's written procedure; no component may be substituted or re-sequenced.

Counterweights and counter-jib are installed in the sequence the manual specifies so that the slewing assembly remains balanced at every intermediate stage of erection.

Before climbing, the upper works' centre of gravity is brought over the mast by placing the trolley and hook per the manufacturer's diagram; the crane is unloaded and the jib is locked against slewing as specified.

Climbing pins, wedges, or guide shoes must be fully engaged to carry the upper works before hydraulic ram pressure is released; hydraulics are a positioning device, not a support.

Free-standing height is limited by the manual; beyond it, tie frames are installed at the specified levels and the building structure at each tie must be verified by an engineer for the imposed horizontal loads.

Typical erection wind limit is around 10–12 m/s (22–27 mph) at the jib because partially assembled components present large sail area with little stability.

After every climb: verify mast bolts or pins installed and torqued to specification, guide roller clearance set, hydraulic pressure correct, and the load moment system and limit switches updated for the new height.

Disassembly reverses the erection sequence; components are lowered under control with the hoist, and no structural pin or bolt is removed while the part it secures is still carrying load.

Chart values are gross capacity: subtract the hook block, slings, shackles, spreader beams, and all below-the-hook gear to obtain the net capacity available for the payload.

Working radius is measured horizontally from the slewing centre to the vertical hoist line with the load applied - not to the hook or the jib tip.

Capacity depends on jib length, counterweight configuration, and parts of line; using a chart page for a different configuration is an overload.

Two-leg sling leg tension: T = W / (2 sin θ), where θ is the leg angle measured above horizontal; at 30 degrees each leg carries the full load, at 45 degrees 0.71 W, at 60 degrees 0.58 W.

Load moment equals load times radius; the load moment limiter compares measured moment against the rated moment for the current configuration rather than against load alone.

Rated capacities carry design safety factors per ASME B30.9: wire rope slings 5:1, alloy chain slings 4:1, synthetic web slings 5:1 - these factors are already built into the rating.

Any lift off the chart, at a radius between charted values, or with an unknown load weight is a stop-and-verify decision, not an estimate.

The centre of gravity must be below or within the rigging attachment points; an off-centre pick tilts the load and loads individual legs beyond their calculated share.

Stop lifting when wind at the jib reaches the manufacturer's in-service limit, commonly around 20 m/s (45 mph) - but reduce capacity earlier for loads with large sail area.

Tandem lifts: each crane's share should not exceed 75 percent of its rated capacity at the working radius, and the total load should not exceed 75 percent of the combined ratings; a qualified person plans the lift.

Only one designated signalperson directs the operator at a time; hand signals per OSHA 1926.1419 or radio communication must be maintained continuously.

The anti-two-block device must be function-tested before each shift and never used as a routine stopping point; the operator must not rely on the hoist limit switch.

Every load is controlled with tag lines where rotation or swing could occur; no personnel stand or pass beneath a suspended load or within the fall zone.

The load moment limiter typically warns as rated moment is approached and stops moment-increasing motions at or before the rated value; it may not be overridden except by an authorized person under a defined procedure.

A trial lift - raising the load a few centimetres - verifies balance, rigging security, and brake holding before the load is moved into the public or work area.

Riding a hook or slung load is prohibited except with an approved man basket and a specific engineered procedure; tower cranes normally are not used for personnel lifting.

Shift inspection is performed by the operator before each shift: wire rope, hook and latch, brakes, limit devices, load moment system, anemometer, and structural members visibly in view.

Frequent inspections are conducted at intervals between shift and annual; a comprehensive annual inspection by a qualified person is required at least every 12 months and must be documented.

Wire rope removal criteria include six or more randomly distributed broken wires in one lay, three broken wires in one strand in one lay, and any heat damage, kinking, bird-caging, or core protrusion.

Hook removal criteria: throat opening increased more than 15 percent, twist more than 10 degrees out of plane, or any crack, excessive wear, or malfunctioning latch.

Tower cranes are fitted with a wind speed indicating device readable by the operator; wind at jib height, not ground level, governs lifting decisions.

Out-of-service configuration is the manufacturer's storm position: hook and trolley placed as specified, slewing brake released to allow weathervaning, and rail clamps or storm anchors applied for rail-mounted units.

Bolted and pinned connections, slew ring fasteners, and tie frame connections are torque-checked on the manufacturer's interval and after any climbing or tie installation.

Any deficiency affecting safe operation requires lockout of the crane until repaired by a qualified person; the repair is recorded in the maintenance log before the crane returns to service.