The vessel was in DP operation and carrying out crane
work operations. The crane was on stand-by for the next operation.
It has two hooks, one main hook and one whip-line hook.
On the deck the riggers were working. To prevent uncontrolled movement of the crane the whip line hook is connected to an internal constant tension tugger winch with a constant tension of 4 tons.
During the start up procedure for the crane the pump
for the tugger winch was not started. That means that the whip line did not follow and adjust according to the movement of the crane boom.
When the boom moved the tension on the whip line became more than 4 tons. The breaks on the winch opened up, causing the tightened whip-line and whip-line hook to gather towards the deck and almost strike one of the riggers standing beside the main hook.
The weight of the whip-line hook is about 1200kg.
The vessel stopped operation and had a time out meeting. A warning note was put up in the crane, new checklists were made and the startup procedure of the crane will be reviewed.