IMCA Warns Diving Bell Could Have Dropped After Lift Wire Failure

The International Marine Contractors Association has warned that a saturation diving bell could have been dropped from a dive support vessel due to a lift wire connection failure discovered during maintenance. Described as a high potential near miss, the incident involved through-wall cracks in the swivel unit connecting the bell to its main lift wire. The defect was identified before catastrophic failure could occur, prompting IMCA to urge operators to check all similar in-service units and review inspection regimes.

 

Details of the Incident

 

The association has issued a warning about a serious near miss. It described the event in a Safety Flash published on 12 August 2026. The incident involved a saturation diving bell on a dive support vessel. The bell was permanently installed on the vessel. The failure related to its main lift wire connection.

The defect emerged during routine maintenance work. During annual maintenance, the top of the swivel unit was examined. It was inspected visually and using a dye pen. No issues appeared on the top eye bolt section initially. This inspection took place while the unit was fitted to the bell.

 

Discovery of the Cracks

 

The full extent of the problem emerged only later. It became necessary to move the main swivel to the workshop. There a through-wall crack was found on one side of the unit. Further investigation revealed a second crack on the opposite side. The two cracks measured 22 millimetres and 38 millimetres respectively.

A further potential defect was also uncovered. The grub screw was removed during the examination. This exposed what could be a full-length crack. The crack appeared to run throughout the threaded area. This added to the severity of the discovered defects.

 

The Equipment's History

 

The equipment had a substantial record of maintenance. It had regularly undergone routine maintenance procedures. This included weekly non-operational testing of the launch and recovery system. Six-monthly and annual load testing was also carried out. Annual DNV surveys took place at class renewal.

The bell had seen significant operational use. New wires were installed in January 2025. In total, 118 bell runs were undertaken during 2024 and 2025. The maximum deployment depth was 65 metres. An additional run of 200 metres was completed in November 2025 to re-spool the wire.

 

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Operating Conditions

 

The vessel operated in a consistent environment. Temperatures stayed fairly constantly in the high 20s to mid-30s Celsius. Humidity levels were high throughout. No bell run had ended early due to adverse weather. Operational conditions were described as relatively benign.

The bell's installation limited its environmental exposure. It is part of a built-in system on the vessel. It is not exposed to direct harsh environmental conditions. The swivel is not generally removed from the bell. On this occasion it was removed due to misalignment of the spelter socket.

 

What Went Right and Wrong

 

The outcome had a critical positive element. The defect was identified before a potential catastrophic failure. No spare unit was available at the time. A spelter socket was sourced as a replacement. This followed discussions with class and the manufacturer under change procedures.

However, the incident exposed serious risks. A critical component in a man-riding lift path had failed. In theory this could have caused a dropped bell during operations. The company sourced a new unit as a replacement. That new unit failed during manufacturer testing and could not be separated afterward.

 

Cause and Lessons

 

The root cause remains under investigation. The unit is made from two stainless steel components. A male threaded end feeds into a female section for load bearing. A grub screw secures the unit's orientation. Stainless steel is prone to galling, though its role in the failure is unknown.

The association set out clear actions for the industry. The swivel unit was taken out of the load path. The faulty component was sent to the manufacturer for investigation. All in-service units of this type should be checked. Inspection regimes should be reviewed and enhanced, with shorter inspection intervals worth considering until a root cause is established.