NZ Certificate in Cranes common mistakes
NZ Certificate in Cranes · Understand the traps and how to avoid them.
Calculating the working load limit from the crane's rated capacity alone, without deducting the weight of the hook block, slings, spreader beam, and any attached lifting gear before comparing to the load weight.
Candidates memorise the load chart figure as 'what the crane can lift' and treat rigging weight as negligible, especially on small loads where the percentage error is hidden.
What to do instead
Work every practice problem in a fixed sequence: gross load = load + lifting gear + hook block allowance; then find rated capacity at the actual radius and configuration; then confirm gross load is at or below that figure. Write the gear weight down as a line item every time, even when it is small.
Reading the load chart at the boom length or radius the operator intends to use rather than the radius actually achieved after the boom is telescoped and the load drifts outward during the lift.
Candidates confuse boom length with radius, and forget that radius is measured horizontally from the slewing centre to the load's centre of gravity, not along the boom.
What to do instead
Practise converting between boom angle, boom length, and radius using the chart's geometry, and always add a margin for load swing and boom deflection. On the job, mark the maximum permitted radius on the ground and stop the lift if the load passes it.
Treating the sling angle factor as a single value for the whole lift instead of calculating each leg separately when legs are at different angles to the vertical.
Candidates learn one rule of thumb (for example, 45 degrees roughly doubles leg tension) and apply it uniformly, missing that a multi-leg sling with unequal angles shares load unequally.
What to do instead
For each leg, resolve tension as (share of load) divided by the cosine of that leg's angle from vertical, and check that no leg exceeds its WLL. Where angles are unequal, treat the steepest leg as carrying the most and verify it explicitly.
Confusing the crane type's defining characteristics when classifying a machine, for example describing a tower crane as a mobile crane with a luffing jib, or mixing up pick-and-carry and static lifting duties.
The terminology overlaps in everyday speech and candidates learn type names without the structural features that define them, so exam scenarios about configuration selection trip them up.
What to do instead
Build a comparison table with columns for jib type, mounting, travel capability, typical duty cycle, and typical site. Test yourself by describing a machine from its features alone without using its name, then naming it.
Writing a lift plan that lists hazards but omits the exclusion zone geometry, the communication method between rigger and operator, and the abort criteria for the lift.
Candidates treat the plan as a risk list rather than an operating document, and copy generic hazard wording instead of site-specific controls.
What to do instead
Structure every plan against a fixed checklist: load data, crane configuration and capacity check, ground bearing, exclusion zone dimensions, roles and signals, sequence of moves, environmental limits, and explicit stop conditions. If a section is empty, justify why rather than leaving it out.
Rigging a load without confirming the centre of gravity, then discovering the load tilts or the sling legs load unevenly once tension is taken up.
Candidates focus on the sling hardware and forget that an off-centre pick changes both the load's attitude and the tension distribution between legs.
What to do instead
Before attaching, identify or estimate the CoG and place the hook vertically above it; for asymmetric loads, use a test lift of a few centimetres to observe tilt, then adjust leg lengths. Include a CoG statement in every rigging plan.
Assuming ground conditions are adequate because the crane is on a hardstand, without checking for voids, buried services, or the bearing capacity under outrigger mats.
Candidates equate visible surface with support, and outrigger loads are far higher than the machine's own weight suggests, so the failure is invisible until penetration occurs.
What to do instead
Calculate or obtain outrigger point loads, compare against a ground assessment, and specify mat size and type. Treat any excavation, service trench, or recently filled area as a void until proven otherwise, and recheck after rain.
Skipping pre-use inspection items that are not visually obvious, such as wire rope broken wires in the valley of a strand, hook latch function, or limit switch operation.
Candidates run through a mental checklist of what they can see from the ground and never test function or inspect rope at close range.
What to do instead
Use a written pre-start checklist with a functional test step for each safety device (limit switches, alarms, brakes, rated capacity limiter) and a close inspection of rope over a full lay length. Record the result, not just a tick.
Giving the load a single signal and then turning away, so the operator and rigger lose a common reference during a blind lift or a load travelling out of sight.
Candidates underestimate how quickly a load moves out of the operator's view and assume the rigger will keep watching.
What to do instead
Agree the signalling method and the person responsible before the lift, use radio or hand signals consistently, and stop the lift whenever the operator loses sight of the load or the signal. Rehearse the emergency stop signal as part of the briefing.
Answering questions about environmental and operational limits with a single wind speed figure, ignoring the manufacturer's deration for boom length, load sail area, or the difference between in-service and out-of-service limits.
Candidates memorise one number and do not connect it to the configuration-specific chart notes where the real limit is stated.
What to do instead
Learn the principle rather than the number: the limit is whichever is lower of the manufacturer's chart note for that configuration and the site rule, and it applies to the load's sail area as well as the crane. Practise reading chart footnotes and stating which limit governs.