What did the reporters tell us?
At midnight, during engineer handover, the main engine auxiliary blower fault alarm and a CO2 high pressure alarm activated. CO2 had been released and was visible; the engine room was evacuated. Upon investigation in the CO2 room it was noted that the pilot operated section valve was in open position. After depressurisation, this was closed manually.
The lessons to be learnt
The O rings of the valve assembly had become brittle, causing a leak to develop from the pilot cylinder. In addition, ball valves in the fire station were found to be leaking. This led to the activation of the CO2. It was subsequently determined that the control valves of the pilot cylinder had not been inspected during an annual service, that the ball valves had never been pressure tested, and that the pilot lines had never been blown through.
The CHIRP Maritime Advisory Board highlighted that heat, humidity and time will degrade systems. Manufacturers should take this into account in the maintenance sections of their manuals, highlighting guidance on contractor and ship staff maintenance periodicities. Similarly, planned maintenance systems on board should be robust and comprehensive. For more modern systems, the increasing use of technology calls for specialist skills; these may be costly or in short supply. The UK Marine Accident Investigation Branch has encountered incidents of this type in the past.
CHIRP has also received a separate report of an inspection during which manufacturers’ locking pins were still in place on the whole CO2 system which was thus rendered ineffective.
“Least used, most needed”. When a fire, flood, person overboard, or other major emergency occurs, the immediate response systems must work immediately, first time. There is no room for failure or delay. This account of a CO2 system in non-operational condition amounts to a serious threat to life. The implications for installation, maintenance and system knowledge are clear.