Line parting as a result of socket failure during grapnel operations

The incident occurred as grapnels were being recovered during attempts to snag, capture and recover a cable on the seabed.

The end of the rope pulled out of its socket, releasing the rope down the aft deck and overboard. A bar at the stern was damaged and a camera and floodlight were carried overboard.

• Higher than expected tensions were experienced during the recovery. At the time of the incident rope tension was observed to be 175 kN.
  
  
• During watch handover, the situation regarding high tensions (averaging 130-140 kN) was properly explained.
  
  
• The aft deck and “Snap Back Zones” were kept clear as per normal practice.
  
  
• The “Atlantic bar” was in place on the stern sheave.
  
  
• All ropes had been inspected (as per toolbox talks conducted and recorded) during pay-out and recovery, and there was no sign of excessive degradation to the failed rope or fitting prior to the incident.
  
  
• The recovery of the grapnels at higher than expected tensions, handover and safety briefing in unusual operation conditions, and back deck/snap-back zone safety were all handled diligently and professionally.
  
  
• The rope failed at less than the minimum breaking load (MBL) of the rope, which was 25.0 tonnes:
  
  
  • Tensions of up to 200 kN (app. 20 tonnes) had been experienced during the recovery.
    
    
  • The working load limit (WLL) of the rope would have been 12.5 tonnes (app. 125 kN) which was adequate for the expected tensions (app. 100-120 kN / 10-12 tonnes).
    
    
• It is possible that the rope socket had gradually degraded over the previous 10 grapnel drives, but with no obvious visual signs of having done so.