Lifting equipment failure: Objects dropped into moonpool

A member has reported an incident in which a chain hoist failed causing a 700kg load to fall into the moonpool. The incident occurred when crew were moving moonpool carriages and frames into position during mobilisation of multibeam echosounder equipment through the moonpool. The moonpool carriage was successfully positioned. As the crew lowered the second moonpool frame into position, the chain on the hoist crane suddenly parted and the frame and carriage fell into the moonpool damaging one of the stopper bars on the wall of the moonpool before being stopped by the other stopper bars.

There were no injuries. There was some damage to the stopper bars and brackets.

Our member’s investigation noted the following:

• Before starting the job, all personnel involved took part in a toolbox meeting and job safety analysis (JSA). A permit to work had been granted;
• The first lift, using the crane in remote control mode, was successful;
• The hoist crane had a safe working load (SWL) of 5 tons;
• The immediate cause of the incident was found to be that during the lifting of the frame, it was obstructed by one of the bracket stoppers;
• The underlying cause was stress and subsequent failure of the chain of the hoisting crane;
• The root causes were:
  • Lack of specific procedure regarding lifting a moonpool frame
  • Lack of awareness from crew who handled lifting moonpool frames to ensure smooth process during lifting.

The following corrective actions were taken:

• Update annual load test to include dye penetration test to check for unseen cracks on hoist chain;
• Update procedures and JSA for moonpool activity;
• Replace hoist and chain and repair stopper bar inside moonpool;
• Defective chain sent to certified third party testing for examination of strains caused by overstressing.

Members may wish to refer to the following similar incidents (key words: chain, failed):

• Offshore tank container rigging failure
• Near-miss: Safe use of chains in rigging