High potential dropped object – chains

What happened?

A set of heavy chain links, or ‘Brothers’ used in lifting, fell from a turbine tower onto the front deck of a Crew Transfer Vehicle (CTV) below.  The incident occurred when loads were being lifted to the transition piece level of an offshore wind turbine tower using a davit crane.

After lifting two loads, the crane operator released the three hooks on the lifting bags and raised the crane hook up using the hand pendant while another crewman started to manually operate the crank handle to slew the crane hook towards the CTV, ready to lift the third load.  Instead of raising the crane hook and attaching ‘Brothers’ above the height of the transition piece gate handrail, the crewman raised the hook approximately 50mm above the transition piece gate handrail and once the crane hook was nearly slewed to the gate, stopped the lifting operation and manually re-position the set of ‘Brothers’ over the handrail before continuing lifting operations by lowering the load while slewing continued.

The practice of manually repositioning the ‘Brothers’ was intended to make the lifting operations slightly quicker; however, it resulted in the bottom handle of the crane hook impacting on the top of the transition piece gate handrail, making the crane hook open and the crane hook itself tilted.  This then resulted in the set of ‘Brothers’ falling onto the front deck of the CTV below.  There were no injuries.

What went wrong?