Fire to welding return cable in cargo tank

During planned hotwork welding activities within a cargo oil tank onboard a floating facility, a small fire was identified to a coupling between two lengths of welding return cable.

The coupling was located at approximately 10.5m height from the bottom of the tank. It was noted that the two cables were ‘knotted’ together in way of the coupling; a common technique used when joining welding cables together to prevent accidental detachment of the coupling and reduce strain to the couplers.

The fire was minor and extinguished with ease following appropriate firefighting techniques. No persons were harmed during this event and no damage noted to the structure as a result of this incident.

Findings / Cause:

The fire was likely a result of increased resistance across the mating faces of the cable couplers, generating excessive heat as current was passed across the coupler.

Although the welding cables were subject to PUWER checks and examined for damage prior to offshore mobilisation, they were not uniquely identified and tracked in the contractor’s maintenance management system. Evidence of deterioration to the sheathing in way of the couplers, degradation to the cable terminations within the cable couplers, and tarnishing/dirt noted to the faces of the brass coupler components.