IMCA Safety Flash – May 2009

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Super Puma Helicopter Accident – Initial Report

The UK Air Accidents Investigations Branch (AAIB) has issued its initial report into the recent Super Puma helicopter accident.

Although this report relates to a North Sea incident, the relevant issues and the information regarding the gearbox monitoring and warning systems on the helicopter type mentioned could apply anywhere.

Fatality During Lifting Operations

A member has reported an incident in which a fatality occurred during lifting operations. The incident occurred on a drillship while attempting to land a christmas tree (XT), using one of the vessel cranes, on to the XT trolley (see general view below).

It was important to centralise the XT, which weighed 50 tons in air, on to the trolley. Centralising guides were in place on the trolley but lifting conditions (heavy load, near vertical crane boom position and movements of floating unit) required significant planning and supervision for this operation.

Failed Nipple on Bolt Tensioning Jack

A member has reported an incident in which a nipple failed on a bolt tensioning jack. A diver was carrying out bolt tensioning on a 24″ pipeline being connected to a pipeline end manifold (PLEM) flange when the nipple flew out of the jack whilst the system was pressurised and hit the diver. There were no injuries.

On investigation it was noted that an incorrect bolt tensioning jack assembly had taken place when a nipple intended for the interconnecting whips had been installed instead of the recommended correct one. The difference in thread size is quite minimal but can be easily identified visually by the different size orifice. Whenever the incorrect nipple comes loose through constant utilisation, this difference is sufficient for it to be forced out when hydraulic pressure is applied to the system.

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