Reliance on crane limits caused crane damage and dropped objects

The incident occurred when a crane operator, whilst attempting to stow the block during the hours of darkness, had difficulties in seeing it due to poor lighting conditions and the boom angle of the crane. Consequently, the crane operator relied on his upper crane limits to stop the block. The upper limit switch failed to operate due to a technical fault and the wire socket was pulled into the sheave causing damage to the sheave, wire and rope guard. Sheared bolt heads from the rope guard then fell to deck in the vicinity of personnel below.

The crane operator then immediately lowered the block to position where he could cancel the alarms which were now sounding. This action itself could have released further potential dropped objects which may have been held in place by the block.

Investigation noted that:

• The incident took place during a ‘routine’ task and was considered low risk, but had the potential for a fatality or serious permanent injury had a larger component fallen and struck any of the personnel below. Additionally, there could have been a substantial impact on the project or vessel schedule with the crane being out of service for a long period of time.
  
  
• A significant contributory factor in this incident was the failure of the crane upper limit switch to automatically stop the wire socket well in advance of the rope guard and sheave. However, the crane operator failed to perceive the risk of ‘two blocking’ the crane even when faced with poor visibility of the boom tip, and relied upon the limit switch to safely stow the block.
  
  
• The lighting conditions, boom angle and poor visibility should have prompted the crane operator to request assistance from the deck crew. As soon as the incident had occurred, the situation should have been assessed prior to lowering the block and possibly releasing any potential dropped objects.