High Risk Work Licence - Derrick Crane (CD) common mistakes
High Risk Work Licence - Derrick Crane (CD) · Understand the traps and how to avoid them.
Reading the load chart only at the radius the operator intends to use, then operating without re-checking capacity as the boom or jib is slewed, luffed, or the load is walked inward or outward.
Candidates memorise a single 'safe capacity' figure for the crane and treat it as fixed, rather than treating capacity as a function of radius, reeving, and configuration. Derrick charts are especially radius-sensitive because the load radius changes with guy geometry and boom angle.
What to do instead
Practise reading the chart as a curve: for every planned lift, record the radius at pick-up, at the furthest point of the slew, and at set-down, and confirm the lowest capacity governs. Build a habit of re-verifying radius whenever the boom angle, guy tension, or load position changes, and state the governing radius aloud during the pre-lift briefing.
Rigging the load with a sling angle or hitch that is not matched to the load's centre of gravity, so the load tips or the sling legs are overloaded even though the load mass is within capacity.
Candidates focus on gross load mass and ignore sling angle multipliers, the number of legs sharing load, and the effect of an off-centre centre of gravity. They also confuse vertical and choked hitch capacity reductions.
What to do instead
Before every lift, calculate the tension in each leg using the sling angle from horizontal, apply the hitch-type derating factor, and confirm the sum of vertical components equals the load mass. Mark or test the centre of gravity on an asymmetric load and position the hook directly above it, using a spreader or two-point lift where needed.
Accepting a hand signal or radio call from anyone on the site rather than confirming that the person directing the lift is the designated dogger or rigger with a clear line of sight.
Candidates treat communication as a courtesy rather than a control, and they are reluctant to challenge a supervisor or bystander who waves the load on. Ambiguity in who is directing the lift is a recurring source of wrong-motion incidents.
What to do instead
At the pre-lift briefing, name the single person authorised to signal and agree the emergency stop signal for anyone. If the signal source is unclear, hold the load and re-establish contact before moving. Practise stopping on an unrecognised signal and treating any two-handed or repeated signal as a stop until clarified.
Skipping or partially completing the pre-operational inspection, particularly the condition of guys, anchor points, rope terminations, and the ballast or counterweight fixing.
Candidates conflate the daily inspection with a quick visual glance and assume the previous shift or the maintenance crew has covered structural items. Derrick-specific items such as guy tension and anchorage condition are unfamiliar compared with mobile crane checks.
What to do instead
Use a written checklist keyed to the specific derrick configuration and sign it off each shift. Inspect guy ropes for broken wires, corrosion, and correct tension; verify anchor pins and foundations for movement or cracking; confirm ballast is secured and matches the chart. Record defects and tag out until rectified.
Setting up or operating without verifying that the supporting surface and foundation can carry the imposed loads, including the pull-out forces on guy anchors.
Candidates think only about the crane's own weight and the load, forgetting that guyed derricks impose large horizontal and uplift forces on anchors and that soft or sloping ground reduces bearing capacity.
What to do instead
Obtain or calculate the maximum anchor reactions and ground bearing pressure from the manufacturer's data, then confirm the foundation and anchor design meet them with margin. Inspect for underground services, voids, and previous excavation, and use designed anchor blocks or piles rather than ad hoc stakes.
Treating the load chart capacity as the safe working limit without applying the derrick's configuration-specific deductions for jib, fly, auxiliary head, or non-standard reeving.
Candidates learn one chart and apply it to every configuration, missing that added jib sections, different rope parts, or a changed boom length each carry separate ratings and deductions.
What to do instead
Identify the exact configuration from the manufacturer's manual before consulting the chart, and select the matching chart page. Where a configuration is not listed, treat the crane as out of service until the manufacturer or a competent engineer provides a rating.
Responding to a load becoming snagged or a guy slackening by continuing to hoist or slew to 'free it', rather than stopping and reassessing.
Candidates underestimate how quickly a snagged load or a slackened guy transfers load into the structure, and they feel pressure to keep production moving. The resulting shock load can exceed capacity without any visible overload.
What to do instead
Adopt a stop-and-assess rule for any snag, unusual noise, guy slackening, or unexpected load swing. Lower the load to a safe position, inspect guys, anchors, and rigging, and only resume after confirming nothing has been overstressed. Brief this rule as part of every lift plan.
Dismantling or de-rigging the derrick in an order that releases guys or ballast before the boom and load path are secured, or without a documented sequence.
Candidates follow the erection sequence in reverse by memory and skip steps, not realising that derrick stability depends on a specific balance of guys and ballast throughout the dismantling process.
What to do instead
Work from the manufacturer's written dismantling sequence, with a nominated supervisor signing off each stage. Confirm the boom is lowered and restrained, the load path is clear, and remaining guys are adequate at every step before releasing any component. Never release ballast or a primary guy while the boom is raised and unsupported.
Relying on verbal instructions and memory for the lift plan instead of a documented plan that names the load mass, radius, rigging, signal person, and exclusion zone.
Candidates see paperwork as bureaucracy and believe experienced operators can improvise. Without a written plan, assumptions about load mass and radius go unchallenged and the exclusion zone is never formally set.
What to do instead
Produce a short lift plan for every lift, however routine, covering load mass and centre of gravity, rigging and sling angles, governing radius and capacity, signal person, and barriers. Brief it to the whole team and keep it on site for the duration of the task.
Estimating load mass from appearance or a supplier's verbal figure and proceeding without verification, especially for fabricated items, wet loads, or loads with attached rigging.
Candidates trust visual judgement and forget to add the mass of spreaders, slings, and any residual material, and they rarely check markings or weigh tickets. Derrick charts leave little margin for an underestimated mass.
What to do instead
Obtain mass from drawings, weigh tickets, or a calculation, and add the rigging and any residual contents. If the mass cannot be established with confidence, weigh the load or treat it as unknown and do not lift. Record the verified mass in the lift plan before rigging.