Crane tip-over threatens protected waters

Lookout! Issue 30, December 2013

Oil booms had to be deployed in the pristine waters of a World Heritage site after a crane tipped over while working on a barge.
Maritime New Zealand ©2020
The 55 tonne crane fell onto its side while extracting piles, and oil was spilt into the pristine waters of a World Heritage site.

The 55 tonne machine was working on an unpowered barge when it fell onto its side, spilling oil into the water. When the incident occurred, the crane was extracting temporary staging piles and then slewing around and driving or ‘parking’ them on the other side of the barge.

After five of the piles had been successfully repositioned, the barge needed to be relocated closer to the sixth pile to ensure it was within the crane’s radius. The operator then extracted the pile, raised the boom to allow for the vibro hammer and pile on the hook, slewed the machine around to the left, lowered the pile to water level and began lowering the boom.

He heard a warning alarm and immediately tried to stop the boom lowering. As he did so, he noticed the angle of the barge was changing. The cab door slammed shut and he realised the crane was going over.

He heard a warning alarm and immediately tried to stop the boom lowering. As he did so, he noticed the angle of the barge was changing. The cab door slammed shut and he realised the crane was going over.

Workers standing near crane
The crane, on it’s side.
Maritime New Zealand ©2020

As the crane tipped, the lower part of its 33 metre boom caught on a temporary pile that had been parked about 15 metres away. This prevented the entire crane from dropping over the side of the pontoon and into the 4-6 metre deep water.

All of the spilt oil was cleaned up using equipment at the site, and an extra boom was laid as a second line of defence. Together, these measures prevented the further spread of oil in the area and any long-term effects from pollution.


  • While any marine pollution is a serious matter, an oil spill in a world-famous national park would have major repercussions for the natural environment and result in harsh penalties for those held responsible. In this incident, the operator was able to quickly deploy equipment to clean up the oil spilt and avert any significant or lasting damage to the environment.
  • The crane operator, who was fully trained and had more than 22 years’ experience operating cranes, was uncertain how or why the machine had tipped over. He believed the crane was in the centre of the barge at the time of the incident.
  • Another worker at the site said he had earlier noticed the crane track coming off a baulk by 100–200 millimetres, but didn’t report it at the time. There had been no evident effect on the barge’s stability and the worker’s observation wasn’t able to be substantiated. Had the worker immediately reported what he’d seen, action could have been taken to identify whether this could cause any problems.
  • A mechanical investigation didn’t identify any failure or fault that may have affected the equipment, and an independent inspector also failed to find any structural flaws in the crane.
    • Investigators concluded that the event was probably the result of operator error, involving the machine being operated outside of its normal charted radius.
  • Employees and employers must take health and safety seriously and have measures in place to deal with any potential risks and hazards. While the cause of the capsize was not conclusively proven, the company took immediate steps to improve safety and hazard management, both at the worksite where the incident occurred and for all of the company’s other crane operations.
    • Measures taken to prevent a repeat of the incident included painting white lines on the deck and across the wooden baulks the crane tracks sit on, as a visual reminder to the operator.
    • Two more inclinometers were built for the project after investigators found that if the crane slewed around 360 degrees, the operator couldn’t keep line of sight with the existing inclinometers.
  • During the incident, the crane operator’s door jammed and the operator and another worker had to force it open. Had the crane ended up in the water, the operator could have been trapped in the cab, with serious consequences. The door was serviced to prevent it jamming. All of the company’s cranes operated on water now have a hammer installed within easy range of the operator, to be used to break the windshield glass and exit the cab in an emergency.
  • The company reviewed its health and safety procedures and operator training to ensure they were up to date and appropriate both for the work undertaken and the environment the crane was operating in. It also gave operators a formal toolbox talk about safe operating procedures and issued a safety memorandum.
    • The advice reinforced the requirement for crane operators working over water not to lift a track off the baulks under any circumstances, and for staff to immediately report any unsafe acts or conditions they observe.

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