Maritime NZ (New Zealand) has produced a safety update to advise of the potential problems and risks that can occur from fixed gas fire extinguishing systems on vessels, focusing on CO2 systems.
A fixed gas fire-extinguishing system is a gaseous substance (often CO2) in a cylinder separate from, but connected to, a protected space and is used to fight a fire. Commonly fixed systems are installed for engine rooms and pump rooms. After air vents are closed and the area sealed, the gas is released in bulk quantity to flood the protected space and smother the fire.
There are many challenges occurring from these fire extinguishing systems, one of which is when the air is not tight. The system will be ineffective if the protected space is not fully closed down.
Even though CO2 is heavier than air it will be less effective if external air can feed the fire. Maritime NZ recommends that flaps and other air pathways should be entirely closed before the fire suppressor is released.
Another safety risk is the unknown structural design issues that could arise, meaning any changes to the vessel, such as new wiring, pipes and cabinets, which may impact the effectiveness of fire suppression by inadvertently creating new air pathways.
Crew’s lack of familiarization with the system is another challenge, which to be solved requires additional training, as well as responsible parties should clear each crewmember’s role.
Knowing how the system works supports the right actions – both before and during a fire. Given that CO2 has a slight cooling effect the possibilities of re-ignition are high.
Concluding, people can be severely threatened from high concentrations of CO2, keeping in mind that accidental release of CO2 may lead to death, as it happened back in May 2019, when a carbon dioxide leak that occurred on a cargo ship at the Longyan port in Weihai, China, resulting to 10 people loosing their lives and 19 injured.
So, to prevent any of the dangers and concerns expressed above, Maritime NZ presents actions to be taken to ensure safety.
Good design
Under the Maritime Rules you are required to:
– make sure the means of control is readily accessible, simple to operate and grouped together in as few locations as possible [Maritime Rule 42B.20(7)].
– minimise the chances of access to control systems being cut off by fire [Maritime Rule 42B.20(7)(c)].
– provide the ability to close all openings that may admit air or allow gas to escape [Maritime Rule 42B.20(4)]
for CO2 systems, install two clearly marked separate controls: one to release from the storage container and a second valve to allow gas to go into the protected space [Maritime Rule 42B.21(6)].
The ability to test the system should be built into the design. Moreover, before installing any system, consider the following: ambient temperature changes, vibration, humidity, shock, impact, clogging and corrosion that might be expected to occur to the protected space.
Operation and maintenance
During installation and maintenance procedures, always be in line with manufacturer’s instructions, concerning component parts. Include in maintenance schedule – ISM and MOSS as appropriate.
Pay special attention to the proper setting, repair and maintenance of the cylinder valves. Improperly set or maintained valves may result in unintended release of the gas which can have fatal consequences.
Know your vessel
– Know how the fire suppression works.
– Have drawings of all air shut-off systems and sufficient technical data and schematics to show how to test and operate the system.
– Building joints and cable connections move over time introducing leak points.
– Vessel maintenance and modifications may affect the integrity of the boundary of the protected space and system.
– When any vessel construction or repair work occurs, ensure contractors understand the importance of the integrity of air tight spaces.
Signage and training
It is of a great importance to place clear signs marking the position of air shut-off controls, with crew instructions. Also, fire drills should include testing of control valves and the order of actions – use different scenarios.
During safety orientation for new crew, a fire system operations drill must be included.
