High Risk Work Licence - Slewing Mobile Crane C6 (60t) common mistakes
High Risk Work Licence - Slewing Mobile Crane C6 (60t) · Understand the traps and how to avoid them.
Treating the load chart as a single number for the boom length in use, rather than cross-referencing radius, boom length, counterweight configuration and outrigger spread together, and then applying the result without deducting the rigging mass.
Candidates memorise one familiar capacity figure from training lifts and default to it, and they mentally separate 'crane capacity' from 'load weight' instead of comparing gross load against the chart.
What to do instead
Work every chart problem through a fixed sequence: measure the actual radius from the slewing centre to the hook, select the correct boom length and configuration row, read the capacity, then subtract hook block, slings and attachments to get the net allowable load. State each step aloud so the reasoning is visible.
Estimating load mass from a visual guess or from the number stamped on a component, rather than calculating from dimensions and material density and confirming against delivery documentation.
Guessing feels faster under time pressure, and candidates confuse the mass of a single part with the mass of the assembled load.
What to do instead
For every load, calculate volume times density, add all attached components, and compare with any marking or paperwork. If the two figures disagree or the material is unknown, treat the higher value as correct or arrange weighing before the lift.
Setting outriggers on fill, backfilled trenches, service pits or a slope without assessing bearing pressure or using spreader mats sized to the actual load, and extending outriggers only partially.
The ground looks firm at the surface and candidates focus on the crane's stability rather than the soil's capacity to carry the outrigger reaction.
What to do instead
Before setting up, identify underground services and voids, assess the ground type, and calculate the outrigger reaction including load moment. Use mats of adequate area, fully extend all outriggers as required by the chart, and verify level within the manufacturer's tolerance with a level indicator.
Rigging loads without confirming the sling angle factor, using unprotected slings over sharp edges, or assuming a two-leg sling doubles the capacity.
Candidates apply the simple 'more legs means more capacity' rule and overlook that capacity falls as the included angle widens, and they underestimate edge damage and load shift.
What to do instead
Apply the angle factor to the single-leg capacity for the actual included angle, use edge protection and correct hardware, and confirm the load's centre of gravity sits below the hook with the load balanced. Check tags and discard damaged gear rather than downgrading it silently.
Accepting a verbal or radio instruction to move without confirming who has authority, failing to identify a blind lift, and not maintaining a dedicated signal exchange with one nominated dogger.
Candidates want to appear cooperative and responsive, and in noisy or crowded sites the loudest voice is treated as the authorised one.
What to do instead
Establish at the pre-lift briefing who signals, on what channel, and the stop command that anyone may give. Repeat and confirm each instruction before acting, stop immediately on any ambiguity or loss of sight, and never act on a signal from an unidentified person.
Planning a lift near overhead lines by judging distance by eye or assuming that because the crane is not touching the line it is safe, without confirming line voltage or arranging de-energising or isolation.
Candidates underestimate flashover distances and treat the exclusion zone as a single familiar number rather than a voltage-dependent distance.
What to do instead
Identify and confirm line voltage with the network operator, apply the correct exclusion zone for that voltage, and use a spotter or limiting device where required. Prefer de-energising and isolating; if that is impossible, document the control and brief the whole crew before the lift.
Running through the pre-start check as a tick-and-flick routine, missing items such as rope spooling and broken wires, limit switch function, slew brake, outrigger beam condition or tyre and track condition.
Familiarity breeds assumption, and candidates reproduce a checklist from memory rather than inspecting the actual machine item by item.
What to do instead
Use the machine's own inspection schedule, physically touch and test each item, function-test limits and brakes where safe, and record defects with severity. Report any defect that affects safe operation and do not operate until it is cleared.
Confusing duty-of-care obligations with the specific duties of the person conducting a business or undertaking, the crane owner, the dogger and the operator, and answering with a general 'everyone must be safe' statement.
Candidates learn the primary duty of care as a slogan and never map the hierarchy of duties, consultation and reporting obligations onto real roles.
What to do instead
Build a role map: PCBU primary duty, officers' due diligence, designer and manufacturer duties, and worker duties including following instructions and reporting hazards. Practise stating which duty applies to which party in a short scenario.
Treating multi-crane or complex lifts as two independent lifts, ignoring load share, synchronisation, wind and the change of load distribution as the load moves.
Candidates plan each crane separately and do not model how the centre of gravity shifts between hook points during the lift.
What to do instead
Prepare a documented lift study with a nominated lift supervisor, defined load share for each crane, matched reeving and speed, agreed communication and abort criteria, and a wind limit. Confirm the plan with all operators and doggers before starting and stop if conditions depart from the plan.
Finishing a lift without a controlled shutdown: leaving the load suspended or landed without support, failing to secure the crane for wind, or having no emergency lowering or evacuation procedure for a power or hydraulic failure.
Attention drops once the load is down, and emergency procedures are read once rather than rehearsed against the actual machine.
What to do instead
Follow a shutdown sequence: land and secure the load, retract and pin the boom per the manufacturer, apply parking brake and slew lock, chock if required, and isolate. Know the emergency lowering procedure for the specific crane and where the nearest safe landing area is before the lift begins.