NZ Certificate in Cranes cheat sheet

Rated capacity is the maximum load a crane may lift at a stated radius, boom length and configuration; it is set by the manufacturer and modified only by the load chart, never by the operator.

Load moment = load × radius. A crane's stability limit is a moment limit, so doubling radius roughly halves the allowable load for a fixed counterweight and geometry.

Duty classification under AS 2550.1 and ISO 4301 groups cranes by state of loading (light, medium, heavy, very heavy) and class of utilisation; the combination sets design life and inspection intervals.

Slewing with a suspended load induces a side load on the boom proportional to the load and the slewing deceleration; start and stop slewing slowly to keep side load within the chart allowance.

Wind speed at boom height governs operation, not ground-level wind; manufacturer limits typically apply from 20 m/s for large lattice booms, and the load's sail area increases the effect.

The anti-two-block system, rated capacity limiter and moment limiter are safety devices; operating with any of them overridden or isolated is a prohibited practice, not a matter of judgement.

A crane must not be used to lift, hold or transport people unless it is specifically designed and configured for personnel lifting, with an approved platform and a documented risk assessment.

Before each lift the operator confirms the load weight, radius at the point of set-down and pick-up, boom configuration, outrigger or track spread, and ground bearing pressure against the load chart.

Mobile crane families: all-terrain (truck chassis, multiple steering modes), rough-terrain (single cab, 4x4, no road travel), truck-mounted (carrier plus separate superstructure) and pick-and-carry industrial cranes.

Crawler cranes spread load over track area; ground bearing pressure ≈ total weight ÷ total track contact area, and lifting capacity on soft ground is often governed by bearing failure before the load chart.

Tower cranes are classified by base (fixed, ballasted, rail-mounted, climbing), jib type (hammerhead, luffing) and slewing arrangement; luffing jibs suit confined sites because the jib radius changes without tail swing.

Outrigger configuration determines the load chart: full extension on both sides, partial extension, or free-on-wheels. Charts for asymmetric extension require the specific manufacturer data, not interpolation.

Boom length and jib offset change the chart: a longer boom reduces capacity at the same radius because of the greater dead weight and reduced structural margin.

Counterweight must match the configuration in the load chart; adding or removing counterweight without the corresponding chart is a structural and stability hazard.

Gantry and overhead cranes are rated by span, hoist capacity and duty class; the end carriage and runway beam, not just the hoist, must be checked for the imposed wheel loads.

Articulating boom cranes (knuckle booms) are rated by reach and boom geometry; capacity falls sharply as the boom articulates, so the chart is read at the actual boom position, not the horizontal reach alone.

A lift is classified as routine, complex or high-risk; complex lifts need a documented plan by a competent person, high-risk lifts need an engineering design and independent verification.

Plan contents: load description and verified mass, centre of gravity, rigging arrangement, crane selection and position, radii, capacity utilisation, ground conditions, exclusion zone, communication method and contingency.

Capacity utilisation = required capacity ÷ rated capacity at that radius. Common site limits are 75% for routine lifts and 85% for lifts with a documented plan; higher utilisation needs engineering justification.

Every lift plan states the pick-up radius, the set-down radius and the worst-case radius along the path; the governing case is the largest radius combined with the heaviest load.

Ground bearing check: required bearing pressure = (crane weight + load + dynamic allowance) ÷ outrigger pad area, compared with the verified allowable bearing pressure of the supporting material.

Dynamic factors: AS 1418 and load-chart practice apply factors for hoisting (about 1.1), travelling and slewing; shock loading from rapid hoist take-up can exceed the static load several times.

The lift plan is a controlled document: it is briefed to the crew, signed off by the planner and supervisor, and revised if the crane position, load, rigging or ground conditions change.

A trial lift to just clear the ground confirms the load's balance, the rigging behaviour and the crane's response before the load is committed to the full path.

Sling tension in a two-leg sling: T = (W ÷ 2) ÷ cos θ, where θ is the angle from vertical; at 60° from vertical each leg carries the full load, at 30° each carries about 0.58 W.

Sling angle is measured from the horizontal in common rigging tables: capacity factor is 1.000 at 90°, 0.866 at 60°, 0.707 at 45° and 0.500 at 30° of the vertical angle from horizontal.

WLL of a wire rope sling falls with the number of legs and the included angle; a basket hitch around a sharp edge loses capacity unless the bend ratio is adequate and edge protection is fitted.

Centre of gravity must lie below the hook for a stable lift; an off-centre load tilts until the rigging geometry balances, which shifts load between legs and can overload one of them.

Shackles are rated by the pin or bow diameter; the safe working load marked on the bow applies only when the load is along the axis and the pin is fully seated.

Tag lines control rotation and pendulum swing; they must be long enough that the handler stays outside the drop zone and never wraps the line around a hand or body.

Never exceed a sling's WLL by doubling legs without checking the angle: two legs at 120° included angle each carry the full load, so the assembly capacity equals one leg, not two.

Synthetic round slings must be inspected for cuts, abrasion, UV degradation and chemical damage; any sling with a damaged cover exposing the core is removed from service.

Exclusion zone radius is set from the load's potential drop and swing path, not from the crane base; nobody stands under a suspended load at any height.

Pre-start checks: tyres and pressures, outrigger beams and pads, fluid levels and leaks, wire rope for broken wires, kinks and corrosion, hooks for throat opening and latch, brakes, limit switches and alarms.

Wire rope discard criteria follow AS 3569 and ISO 4309: broken wires in a specified length, reduction in diameter, corrosion, kinks, bird-caging or heat damage each require removal.

Hook inspection: measure the throat opening; a hook is removed from service if the throat opening exceeds 10% of its original dimension, if it is twisted more than 10°, or if the latch is missing or defective.

Maintenance is scheduled by the duty classification and running hours; a documented inspection regime covers daily, monthly, six-monthly and annual inspections, with major inspections at defined intervals.

Incident and near-miss reporting is a legal duty; the crane is isolated and inspected by a competent person after any shock loading, contact with a structure, or two-block event.

Communication: one designated dogger signals the operator; anyone may give a stop signal, and radio communication must use a clear, agreed channel and code of signals.

Lifting near power lines requires a spotter and the regulated approach distance for the line voltage; the crane, load and rigging all count as part of the encroaching plant.

Rigging hardware is matched to the load: shackles, hooks and master links are rated components, and the assembly's WLL is the lowest-rated item in the system.

Sling leg load formula: leg load = (load × distance from the leg to the centre of gravity) ÷ the span between the legs; this gives the share each leg carries.

A load is stable when the hook is directly above the centre of gravity; if the hook is offset, the load tilts and the rigging must be arranged to bring the centre of gravity under the hook.

Multi-leg slings: the included angle between opposite legs determines the capacity factor; capacities are tabulated for 0–45°, 45–60° and over 60° included angle, with the last group the most restrictive.

Choker hitches derate a sling to about 75–80% of its vertical capacity; basket hitches can achieve up to 200% of a single-leg vertical rating only if the bend radius is adequate.

Load control during the lift: keep the load as low as practical, use a tag line, avoid side pulls, and never drag a load that the crane is not rated to drag.

Rigging inspection before every lift: check for cuts, broken wires, distorted hardware, missing safety latches, illegible tags and any sign of heat or chemical damage.

Daily pre-use inspection is by the operator; periodic inspections are by a competent person, and the interval is set by the duty classification and the manufacturer's manual.

Structural inspection covers boom sections, pins, chords, welds and the slew ring for cracks, corrosion and deformation; non-destructive testing is used where the manual specifies it.

Brake testing: the hoist brake must hold the rated load without slip; the slew and travel brakes are checked for response and holding ability under the specified test.

Hydraulic systems are checked for pressure, leaks and hose condition; a hose failure on a load-holding circuit can drop the load, so load-holding valves and pilot check valves are verified.

Records: the maintenance log, inspection reports, load test certificates and defect rectifications are retained for the life of the crane and are available for audit.

Load testing after major repair or alteration verifies the rated capacity; the test load and method follow the applicable standard and are witnessed and documented.

Defects are classified by severity; a defect affecting safe operation results in the crane being tagged out and removed from service until rectified and re-inspected.

Standard hand signals are used when radio fails; the dogger's signals are unambiguous, and the operator stops immediately on any signal that is not understood.

The operator keeps the load in view or uses a dogger; if neither is possible, the lift does not proceed.

Slewing speed and load swing: the load lags the boom during acceleration, so the operator anticipates the swing and slows before the set-down point.

Hoist limits: the upper limit device stops the hook block before it reaches the boom head; the lower limit is the amount of rope remaining on the drum, typically at least two or three dead wraps.

Load chart interpolation between radii is permitted only where the manufacturer's chart provides it; otherwise the operator uses the next longer radius, which gives the lower capacity.

Pick-and-carry is a separate chart condition; travel with a suspended load is permitted only where the manufacturer's chart and the site rules allow it, on a prepared route.