Main bell wire rope damaged

What happened?

At the end of a saturation dive, a main bell wire was damaged by the proximity switch bracket (chandelier) being picked up by a single broken strand on the main bell wire rope. The incident occurred during a bell recovery procedure performed by the winch operator. The Moonpool operator stopped the winch operator from further recovery of the bell after noticing that the proximity switch bracket (chandelier) was in the bell launch and recovery sheave. Dive technicians freed up the chandelier from the sheave, and the bell was safely recovered.

The main bell wire rope was three years old, had been visually inspected, and destruction tested with a positive result of 8:1 factory and above the maximum allowable 10% reduction of MBL as per IMCA D018, two weeks before the incident.

What went right

• When the problem was spotted during bell recovery procedure an “All Stop” was called by one of the moonpool operators and all personnel involved supported it;
• There was a focused and swift reaction from operators to remove the chandelier from bell wire rope sheave. This helped to save time during the bell recovery procedure, this was paramount to a safe bell lock on.

What went wrong

A single outer wire rope strand, broken from the bell main wire, lifted the chandelier with the proximity switch into the bell main wire rope sheave.

What was the cause?

Our member noted the following:

• Root cause of the incident: Failure of design. The chandelier was a tight fit which allowed movement when the broken wire passed through. The bell main wire ran through a narrow space within the chandelier allowing a single broken outer strand to be caught up.
• Direct cause of the incident: Equipment damaged. A single outer strand broken from the bell main wire was enough to lift the chandelier with the proximity switch into the bell main wire rope sheave.

Actions

• The proximity sensors and chandelier were relocated attaching it to a solid suitable point on the static side of clump weight wire. This eliminated the risk of reoccurrence. See image on right above;
• After cut back of damaged length of bell wire, Classification Society witnessed load test being performed;
• A dive trial was conducted with an empty bell to working depth to double check suitability and length of bell main wire rope.

Members may wish to refer to:

• Near miss: Single wire strand protruded from original lay
• Near-miss: Fault spotted in subsea lifting wire
• Partial parting of a bell main lift wire

IMCA notes: this flash has been amended to reflect correct terminology with respect to the components of a wire rope: see diagram below. However, for purely practical reasons relating to internet links, the links to previous safety flash incidents relating to wire rope incidents, have not been amended.