Nobody was hurt in the incident on 31st March 2016 – nearly eight years ago – but a chaotic scene ensued after the collapse of the Rowan Gorilla VII’s boom, according to the Health & Safety Executive (HSE).

Flying debris damaged a nearby vessel and whipped a hose out of control before it ruptured, leaving a cloud of cement dust.

HSE inspectors described the incident as an “accident waiting to happen”.

It happened offshore in the North Sea as staff were preparing to recover a faulty submersible pump. As the crane operator raised the boom to clear one of the three legs of the installation it failed catastrophically and collapsed.

HSE found the immediate cause of the crane collapse was that Rowan Drilling (UK) Limited had not checked that a limit switch, designed to prevent the crane boom being raised to the point of mechanical failure, had been correctly set.

Three of the four boom sections fell to sea between the rig and the Solvik Supplier supply vessel, which was pumping dry cement to the rig via a flexible hose. The crane’s auxiliary hook, cables, components, and rig debris landed on the deck of the Solvik Supplier. The boom tip snagged the flexible hose, dragging it below the sea surface, causing it to rupture and whip back onto the deck of the vessel engulfing it in fine cement dust.

Although no one was injured by the incident, there were at least five Rowan employees on and around the crane at the time of the collapse. There were 13 crew onboard the supply vessel.

The HSE investigation found that safety mechanisms, designed to prevent inadvertent operation of the slew, hoist, and boom joystick controls in the port bow crane cabin had all been overridden to prevent them returning to their locked neutral position. An improvement notice was served on the company to remedy issues relating to the limit switches and management issues identified.

Rowan Drilling (UK) Limited, of Queens Road, Aberdeen, pleaded guilty to breaching Section 2(1) and Section 3(1) of the Health and Safety at Work etc. Act 1974 . It was fined £130,000 at Aberdeen Sheriff Court on 21st December 2023.

HSE inspector Brian Kennedy said: “It was pure luck that nobody was seriously hurt or died as a result of these failings. As with so many incidents, the circumstances leading to the collapse of the port bow crane on the RGVII were years in the making and symptomatic of a defective safety management system that allowed those conditions to exist and persist.

“This was quite simply an accident waiting to happen and illustrates the vital importance of maintaining and testing crane limit switches to ensure they will always provide the intended level of protection.”

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