By Alan Lowne

After foundering, fire is consistently the second leading cause of ship losses worldwide each year, and so the implications of the failure of fire safety systems are significant.

CO2 systems are universally relied upon to provide an automated response to the outbreak of maritime fires to ensure that conflagrations are contained and controlled. CO2 gas has excellent fire-extinguishing capabilities and is also relatively inexpensive, but, since it purposefully reduces the ambient oxygen content, it can pose a serious risk to personnel. With CO2 systems, crews must evacuate the area to avoid the lethal effects of the gas. This delay can mean that relatively minor fires escalate, causing loss of life and even total loss of ships. And if the system is not regularly checked and maintained, it becomes ineffective when most needed.

As reported in SAFETY4SEA (May 6, 2021), an ultralarge container ship traveling from Singapore to Hong Kong experienced a fire alarm in the engine room. Not extinguishable with a portable extinguisher, the water mist system also failed to operate, so the crew activated the fixed CO2 system. But upon checking the CO2 room, it was noted that a bottle leakage alarm had gone unnoticed, and several CO2 cylinders and manifold heads remained frost-free and warm, showing that some cylinders had not been discharged. An engineer put on a breathing apparatus in order to release the cylinders manually. After 30 minutes, the fire was extinguished, and the vessel then needed to be towed to the nearest safe port for repairs.

CO2 systems have several limitations, one of which is that gaseous suppression systems need a required cylinder fill level to ensure operability. Since the cylinders are filled to very high pressures (>50 bar) this inevitably causes leakage. Therefore, the CO2 fill must be verified in one of several ways to validate a system’s functional readiness. The conventional method of doing this, weighing the cylinders, often requires a cylinder to be moved and usually detached from the manifold in order to detect agent weight. Crews are not certified to do this, and as such cannot be compliant with IMO SOLAS requirements without having specialist equipment on board. IMO SOLAS FSS Code Chapter 5, 2.1.1.3 states: “Means shall be provided for the crew to safely check the quantity of the fire-extinguishing medium in the containers. It shall not be necessary to move the containers completely from their fixing position for this purpose.”

Despite this requirement, anecdotal evidence suggests that 80 percent of Chinese-flagged vessels are deficient in their CO2 systems, which indicates that agent charge is not being verified on many ships. Agent loss due to accidental discharges can be highly dangerous since CO2 may not be deliverable at the required concentration to properly extinguish a fire.

MSC.1/Circ 1318 outlines the minimum recommended maintenance for fire suppression systems is to confirm at least once every two years that cylinders have at least 90 percent of the nominal charge. Good practice would dictate that cylinders should be assessed more frequently than this since any agent loss could result in the unsuccessful containment of an onboard fire. However, this is rarely done since weighing cylinders requires the system to be switched off and, thus, cannot protect the ship for the duration of inspection. Then each cylinder must be removed from the manifold, requiring two people to carry the cylinder (usually containing 45 kg of CO2) onto a scale and then be returned and recoupled. This procedure can take as much as 15 min. per cylinder. Considering that the average ship may have 600 cylinders, and may only be in port for 4 hr., conducting a rigorous inspection of each cylinder is challenging, to say the least.

The implications of the failure to maintain a CO2 system are significant. Compliance is only one aspect of safety; guaranteeing a vessel is safe for crew can be even more important. Undetected agent loss from a system can have fatal consequences; detecting this quickly and easily can significantly lower a vessel’s risk exposure.

Since the agents are designed to suffocate fires, their inadvertent discharge can asphyxiate humans in their presence. There are numerous examples of this occurring; the unintended release of suppressants from fire-extinguishing systems caused 72 deaths and 145 injuries, mainly in the marine industry, between 1975 and 2000. In the U.K., an example of this occurred in 2019 on the fishing vessel Resurgam when a fire suppression system was being installed. The system was accidentally discharged, killing an apprentice technician who was on board at the time. This was similar to an incident in 2011 at HMNB Faslane when a contractor had to be resuscitated after being exposed to the accidental discharge of a CO2 system while on board the tug SD Nimble. In both instances, the fire suppression system, designed to save lives, threatened to take life.

Ultrasonic Solution

An ultrasonic system of checking can detect liquid levels through a solid cylinder wall. An operator can rapidly and reliably detect the liquid level within a fire cylinder, with a clear discovery of the gas-liquid interface. An ultrasonic pulse is emitted into the cylinder by a transducer held in contact with the cylinder wall. The signal is reflected, returned and analyzed to determine if the contents at that level are a liquid or gas. The sensor can be moved up or down the cylinder to accurately find the liquid-gas boundary. This process can take under 30 sec. with a skilled operator.

An ultrasonic detector is non-invasive: The cylinder is not disturbed, and no manual weighing is required. It is precise and fast. A single operator can reliably measure numerous cylinders with an accuracy of ±1.5 mm in less than 30 sec. per cylinder, even with different cylinder types and sizes.

Ultrasonic level detection provides a faster, easier way to monitor cylinder fill levels. It not only saves the crew time by streamlining the measurement process but consequently allows for monitoring to be done more frequently, improving vessel safety. The ability to guarantee an adequate agent level within a fire suppression system, using a measurement process that can be completed within 30 sec., ensures a vessel’s regulatory compliance.

By removing the need to uninstall and move cylinders to weigh them, ultrasonic monitoring solutions, such as the Portalevel MAX MARINE PLUS, minimize the risks associated with safety procedures by providing a non-invasive measurement process. Cylinders do not need to be detached during the measurement process, meaning the fire suppression system experiences no downtime, and continuous fire safety preparedness is assured. As evidenced by examples of accidental discharge, this can minimize the risk of loss of life on board a ship.

A recent challenge presented itself to Khayber Fire and Security Systems WLL in Bahrain. While inspecting fire suppression systems on naval vessels, the company encountered a common challenge: the absence of standard pressure gauges in FM200 cylinders aboard the U.S. Navy vessels Moulthrope and Glen Harris, as well as the U.K. Navy Ship HMS Lancaster. In this case, Portalevel MAX PLUS enabled Khayber to accurately estimate the liquid levels of the FM200 agent without the need for traditional pressure gauges. An additional instrument, the Portasteele CALCULATOR, enabled them to calculate the actual agent weight, ensuring compliance and safety standards were accurately met with precision, leading to significant operational cost savings. Servicing the 500-lb. cylinders would normally require a team of four to five people due to their weight and difficulty to move. This task was eliminated using ultrasonic level sensing, which proved particularly beneficial in cramped spaces, such as those on the Multhrope, Glen Harris and HMS Lancaster vessels, where manual dismantling of cylinders is impractical.

Ultrasonic monitoring solutions provide the safest possible operation of a fire suppression system, guaranteed by a handheld device that requires significantly less manpower and time than other agent verification methods. If used more widely, it is very likely that ultrasonic verification methods could help improve marine fire statistics.

Alan Lowne is the CEO of Saelig Co. Inc., a distributor for Coltraco Ultrasonics.