Safety Flash
Loss of redundancy in diving bell launch and recovery PLC system
Loss of redundancy in diving bell launch and recovery PLC system
- IMCA
- Safety Flash
- IMCA SF 13/23
- DivingInspection and MaintenanceMachinery and Equipment
- Functional safety
- Diving operationsInspection and maintenance
- Functional testingRisk assessment
- Marine industry
- Vessel
Summary
A diving bell launch and recovery system lost automatic PLC redundancy when a synchronisation module developed a faulty transmitting diode. Unavailable spares delayed repair. Following risk assessment and successful testing of independent processors and manual changeover, the vessel resumed work using temporary manual redundancy. Automatic redundancy was subsequently restored in port.
Classifications: Functional safety; safety instrumented systems; SIS.
Classifications: Diving operations; diving; commercial diving.
Classifications: Inspection and maintenance; asset inspection; equipment maintenance.
Classifications: Functional testing; function test.
Classifications: Risk assessment; hazard assessment.
Classifications: Marine industry; shipping industry; maritime sector.
Classifications: Vessel; aboard ship; onboard vessel.
Summary
During vessel transit to an offshore field, Dive Technicians on a routine walkaround noticed an alarm from the dive bell Launch and Recovery System (LARS). Investigation indicated loss of automatic (LARS) PLC redundancy caused by failure of one of the PLC fibre optic processor synchronisation links. This resulted in the loss of normal operation and increased the risk of single point failure of the LARS.
IMCA SF 13/23. Themes: diving, inspection and maintenance, machinery and equipment.