A recent incident has been reported to IMCA. The 350T/96m long boom of a derrick lay barge (DLB) 2500 short tonne revolving crane broke, crashed onto the deck, fell into the sea, dragging a lot of debris with it and killed a diver working on the sea bed.
The crane was stationary with its boom in a forward position over the DLB deck at an angle of 45°. There was no load on the main hoist which was in a secured rest position. The DLB was anchored on a northerly heading and the sea condition had two metre swells heading east.
The boom failure was caused by the side force due to the rolling movements which ruptured the coupling studs of the boom foot bearings.
It is believed that the incident could have been avoided by adherence to good maintenance/inspections, working practices and to the operating limits of the crane.