High Risk Work Licence - Concrete Placing Boom (PB) common mistakes
High Risk Work Licence - Concrete Placing Boom (PB) · Understand the traps and how to avoid them.
Treating the concrete placing boom as a crane when planning lifts and exclusion zones, and quoting crane lift-study rules instead of the boom's own stability and outrigger requirements.
Both machines are high-risk plant with booms, so candidates carry over crane terminology and assume the same duty-of-care obligations and load-limiting logic apply; the placing boom is a pipeline-delivery machine whose loads are mostly self-weight plus pipeline and concrete, not slung loads.
What to do instead
Build a one-page comparison in your own words: what the boom carries, how it is stabilised, what limits its reach, and which person holds which duty. Practise classifying scenarios as 'crane task' or 'boom task' before answering, and state the boom-specific control (outrigger footprint, pipeline support, wind limit) rather than a generic crane control.
Naming 'the operator' as the sole duty holder for setup and inspection, and omitting the person conducting a business or undertaking, the competent person, the spotter and the concrete supplier from the duty list.
Operator-centric training and day-to-day experience make the person at the controls feel like the whole safety system; candidates under-report shared duties because they have never had to write them down.
What to do instead
Memorise duties as a chain of custody: PCBU sets and funds the system, competent person verifies setup and inspection, operator controls the boom, dogger/spotter manages the exclusion zone, supplier controls delivery. For each question, ask 'who else touches this task?' and name at least two parties with their specific obligation.
Producing a risk assessment that lists hazards only (powerlines, wind, ground) without a control, a residual risk rating, or an owner and review trigger.
Candidates confuse hazard identification with risk management and run out of time, so they dump a hazard list and stop; they also fear being marked wrong for choosing a control hierarchy level.
What to do instead
Use a fixed four-column template every time: hazard, consequence, control with hierarchy level named (eliminate, substitute, engineer, administrate, PPE), residual rating plus who verifies it. Write two full rows in practice under timed conditions so the template becomes automatic.
Choosing administrative controls or PPE as the primary control for boom contact with overhead powerlines, instead of isolation or exclusion distance.
Spotters and signage feel practical and cheap, and candidates have seen them used on site, so they select the familiar control over the higher-order one; they also misremember the hierarchy as 'whatever is available'.
What to do instead
Apply the test 'can the hazard be removed or physically separated?' first. For powerlines, the answer is de-energise/isolation or a verified exclusion distance, with a spotter as a backup layer, never the primary control. Practise rewriting weak controls into higher-order ones and stating why the lower control is only supplementary.
Mixing up boom component names and functions, for example confusing the slewing unit with the turret, the boom sections with the pipeline, or the outrigger beam with the outrigger pad, and describing the counterweight or stabiliser leg as a lifting point.
Terminology is learned orally on site with regional and brand variation, and diagrams in study material look similar at a glance; candidates recognise components visually but cannot define them precisely under exam wording.
What to do instead
Make a labelled sketch from memory, then check it, and write a one-line function for each part: slewing unit rotates the boom, pipeline carries concrete, outrigger beam extends the footprint, pad spreads load into the ground. Drill by describing a component's function without naming it and having the name recalled.
Performing a pre-operational inspection as a walk-around glance, checking only obvious damage and skipping the pipeline, pins, slew bolts, outrigger pads, hose restraints and safety devices.
Time pressure at the start of a pour and familiarity with the machine lead to 'it was fine yesterday' reasoning; candidates also do not know which items are inspection-critical versus cosmetic.
What to do instead
Use a written checklist in fixed order (structure, slew and pins, pipeline and couplings, restraints, outriggers and pads, safety devices, fluids and controls) and state the pass/fail criterion for each item. In answers, name at least three specific items and what a defect would look like, rather than saying 'checked for damage'.
Describing setup without verifying ground bearing capacity and pad load spread, and placing outriggers on backfilled trenches, recently disturbed soil or uncompacted fill without engineering advice.
Ground conditions are invisible in a written question and candidates focus on the visible machine; they also assume 'flat ground' equals 'strong ground' and have never calculated a pad pressure.
What to do instead
Always state the sequence: assess ground and underground services, obtain bearing capacity or engineer's advice where uncertain, use pads sized to spread the load, then re-check level after loading. Practise explaining why a larger pad reduces pressure and why a void under a pad causes a tipping rather than a sinking failure.
Answering boom movement questions with 'move slowly and watch the boom' instead of naming the specific sequencing rules: start with the section that keeps the load line plumb, avoid simultaneous motions, keep the pipeline supported, and never drag the boom or pipeline sideways.
Operating knowledge is often tacit and muscle-memory based, so candidates cannot convert it into explicit rules; exam wording about sequencing feels artificial compared with the feel of the machine.
What to do instead
Write the movement rules as short imperatives and attach a reason to each: one motion at a time (predictable tip load), plumb line under the boom (avoids side load), pipeline supported (prevents whipping), no dragging (avoids lateral overload). Rehearse by narrating a pour aloud in sequence before answering.
Reading the load chart at the maximum reach figure only, ignoring the combination of boom length, radius, counterweight configuration, outrigger spread and wind, and failing to apply the chart's derating notes.
Candidates treat the chart as a single capacity number and skip footnotes; they also do not distinguish between structural limits and stability limits, so they cannot say which one governs at long radius.
What to do instead
Practise reading charts by locating the intersection of two variables, then applying every footnote that matches the setup. State which limit governs (stability at long radius, structure at short radius) and show the margin. Learn to answer 'what changes if the outrigger spread is reduced or wind rises' with the chart consequence, not a general caution.
Describing communication as 'use hand signals' without naming the signal set, the designated signal person, the fallback when line of sight is lost, or the stop command that overrides everything.
Communication is treated as common sense and candidates have worked with informal signals on site; they do not know that only one person should signal and that anyone may call stop.
What to do instead
Answer with the full chain: agreed signal set confirmed at the pre-start, one designated signaller, radio as backup with a tested channel, line of sight maintained or a relay person positioned, and an unambiguous all-stop signal any person may give. State what the operator does when a signal is unclear: stop and confirm, never guess.