Weight dropped to the seabed narrowly missing diving bell

What happened?

Before launch of an Air Diving Launch and Recovery System (LARS) from a third-party DSV, the winch wire for the clump weight/guide weight became lodged between the winch body and the winch drum wall.  As the winch operator paid out on the clump weight, the winch wire tightened on the winch hub and parted.  This resulted in the 300kg clump weight falling to the seabed and narrowly missing a saturation diving bell and divers already deployed near the seabed.  There were no injuries or damage to equipment.

What went wrong?  What were the causes?

• It was not standard operating procedure to inspect the clump weight wire or winch, before launch of the Air Diving LARS;
• There was no pre-use check program in place for operating the LARS;
• The winch operator’s position did not allow a clear line of sight to the winch drum;
• The LARS design enabled a loose wire when the A-frame is in stored position, i.e. a loose wrap became lodged between the winch housing and the winch drum wall.

What actions were taken?  What lessons were learned?

• Consider additional engineering controls, where there is a possibility for winch wire loose wrap movement off the winch drum;
• Ensure adequate equipment pre-use checks are conducted;
• Maintain line of sight to the winch drum during spooling;
• In operations that involve equipment being deployed overboard, consider dropped objects and ensure that adequate ‘drop-zones’ are identified.

Members may wish to refer to:

• Near-miss: Dropped taut wire clump weight (2011)
• Near-miss: Dropped clump weight (2009)
• Subsea lifting and dropped loads (1999)