201120 Simple failures render CO2 system inoperative

Official report: edited from USCG Marine Safety Alert No. 10(b)-10

 A machinery space fire onboard a relatively new vessel was effectively responded to, and extinguished by, the vessel's crew using portable extinguishing equipment. However before it was declared completely extinguished and approximately five hours after the fire started, the master of the vessel made the decision to release CO₂ from the vessel's fixed firefighting system. It failed to operate as designed. Subsequently, crew members were unable to activate it manually and CO₂ was never directed into the machinery space. The following deficiencies were discovered in the CO₂ system:

1. When the system was activated, there were numerous leakages into the CO₂ room from defective and improperly tightened connections.

 

 

2. The zone valve for the aft machinery space which admits CO₂ from the bottle bank manifold to the space failed to open as its actuating arm fell off the valve spindle when the gas powered piston actuator attempted to move it. It was found that the actuating arm was held in place only by a very small machine screw and washer. The valve was able to be moved only after the gas pressure was relieved from the inlet side of the valve.

 

 

3 Actuating arms to five of the six other zone valves were found loose. They were also attached by single undersized screws.

 

 

4. Natural fibre yarn used extensively on pipe threads throughout the system and in some instances, seemed to have entered the system.

 

 

5.Certain sections of the CO₂ piping system allowed the accumulation of water that could not be drained. Consequent corrosion could possibly negatively affect operation of other components.

 

 

6. The CO₂ system's pilot and gang release bottles did not appear to operate correctly and thus each cylinder had to be individually activated, using its valve handle. At least one pilot bottle activation hose was reported to have leaked.

It was later found that the system had been recently serviced and inspected by an authorised service provider.

In view of the above incident, the USCG strongly recommends that regular inspection, maintenance, verification and testing of shipboard fixed firefighting installations must be carried out to ensure that they will operate correctly during an emergency.