Cherry picker boom failure
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CHERRY PICKER BOOM FAILURE. BHPBIO YARRIE MINE SITE – 06 OCTOBER 2005. INCIDENT.

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CHERRY PICKER BOOM FAILURE

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Cherry picker boom failure

CHERRY PICKER BOOM FAILURE

BHPBIO YARRIE MINE SITE – 06 OCTOBER 2005


Incident

INCIDENT

  • At 1245hrs on 06.10.05, Ben Hughes, an electrician working for a contract company constructing a new 22kV powerline at Yarrie minesite, fell approx 8m when the upper boom snapped on the cherry picker he was operating.

  • The fibreglass boom snapped when the basket was driven up into the steel cross-arm on the pole on which Ben was working.

Upper boom

Cross-arm struck by basket

Basket

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Incident con t

INCIDENT (Con’t)

Cherry Picker operated by Ben Hughes

Crane operator also at scene

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Incident con t1

INCIDENT (Con’t)

Control levers to operate the cherry picker

  • Ben was kept within the cherry picker basket when it fell to the deck of the truck on which it was mounted.

  • His life was undoubtedly saved by a combination of good luck and the safety hardness he was wearing.

  • The contracting company had bought the cherry picker second hand approx four months before sending it to Yarrie on its first project. It had all its necessary statutory certifications.

Lanyard attachment point

Ben landed here

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Basic causes

BASIC CAUSES

  • The control levers for the cherry picker, which were mounted external to the basket, became jammed under the cross-arm on the power pole when Ben moved the basket upwards to gain better access to his task. These control levers included the dead-man lever, which became locked in the ‘on’ position. Ben was then unable to operate the controls.

  • The cherry picker powered the boom upwards (while the basket was trapped under the cross-arm) until the upper boom snapped.

  • The pre-existing condition of the upper boom, and the hydraulic circuit that powered the boom, are still being investigated.

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Icam contributing factors

Absent or Failed Defences

There was no protection above the control levers to prevent them from being depressed by inadvertent contact with the cross-arm (or anything similar). This is contrary to Australian Standard 1418.10 that states: ‘The highest point of the control members (knobs, levers, and the like) should be at least 50mm below guardrail level’.

The inspections of the cherry picker both before and after its arrival on the Yarrie site did not identify the lack of a barrier above the control levers as a hazard.

ICAM CONTRIBUTING FACTORS

Control levers exposed above lip of basket

Control Lever

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Icam contributing factors1

Absent or Failed Defences

The upper boom was not strong enough to withstand the force exerted by the hydraulic cylinders, when the bucket was pinned in a fixed position. The boom snapped at the point where it changed from being a fibreglass wrapped steel tube, to being a completely fibreglass construction.

ICAM CONTRIBUTING FACTORS

Fibreglass rod to level the basket (snapped)

4 Fibreglass control lever rods (snapped)

Steel inner tube

2 Hydraulic lines to operate tools in basket

Inspection Hatch

Fibreglass wrap

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Icam contributing factors2

Individual or Team Actions

At some point in time prior to the cherry picker being sent to Yarrie, a protective barrier above the control levers had been removed.

The hazard of the exposed levers was not recognised by the cherry picker operator, the crane operator, his supervisor, nor any of the persons who has previously inspected the machine as being fit to operate. The operators and the inspectors were all experienced at their jobs.

The statutory inspections of the fibreglass boom may not have been sufficiently detailed to reveal deterioration.

Task / Environmental Conditions

Before the cherry picker had been dispatched to the Yarrie site, the contracting company had removed a plastic insulating liner from the basket. The liner was removed because no ‘live’ power line work was to be undertaken on this project. If the liner is removed, then the control levers can be rotated (approx 180 degrees) so that they protrude into the basket and are protected by the upper lip of the basket. This was not done.

ICAM CONTRIBUTING FACTORS

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Icam factors con t

Task / Environmental Conditions

The inspection sheet used to check the suitability of the cherry picker for use on site was not sufficiently detailed or specific to highlight the lack of protection above the control levers.

The condition of the boom and hydraulics prior to the accident were unknown to the those using the machine.

ICAM FACTORS (Con’t)

  • Organisational Factors

  • The cherry picker had been bought second hand by the contracting company without sufficient regard to the state of its safety devices.

  • The insulating liner had been removed from the basket by the contracting company without reference to the manufacturer’s advice to rotate the control levers.

  • Inspection of the sub-contractor’s equipment was not sufficiently detailed to highlight the safety defects pertaining to the arrangement of the control levers.

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Recommendations

Recommendations

  • No cherry picker is to be used that has control levers exposed to inadvertent external contact. A guardrail (or similar barrier) conforming to the requirements of AS1418.10 must be fitted.

  • Inspection protocols for cherry pickers need to be made more specific and rigorous, by paying closer attention to the lifting components of the machine. A suggested inspection list is attached.

  • A thorough inspection is to be carried out on any fibreglass boom for signs of cracking, or corrosion of any internal steel tube section.

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