Recent inspections conducted by DNV have revealed multiple cases of CO₂ fire-extinguishing systems with depleted cylinders, a condition that may critically compromise both fire safety and vessel integrity.
This finding underscores the importance of strict maintenance control and correct testing methods for fixed firefighting systems — a responsibility that lies jointly with ship management and approved service providers.
Key Issues Identified
1. Incorrect use of ultrasonic liquid level gauges
Improper testing procedures have been identified as a main contributor to inaccurate readings.
When ultrasonic level measurements are taken at temperatures exceeding the manufacturer’s specified limit, the CO₂ inside the cylinder may enter a supercritical state, eliminating the liquid phase. In such conditions, the gauge cannot provide a reliable level reading, leading to potential undetected depletion.
2. Bursting disc material fatigue
Another concern involves the bursting disc material used in CO₂ cylinder valves, particularly in systems supplied by NK Co., Ltd. (South Korea) prior to 2016.
According to field experience and the Marshall Islands Maritime Safety Advisory No. 14-23, copper bursting discs have shown a tendency to fatigue-related failure, posing a risk of leakage or reduced system readiness in case of fire.
Recommendations from DNV and Marine Surveyor Consultant
To ensure reliability and compliance with SOLAS and Class requirements, Marine Surveyor Consultant Sagl recommends that shipowners and operators:
- ✅ Keep the latest CO₂ system user manual on board and ensure its procedures are strictly followed.
- ✅ Engage only approved service suppliers, performing system maintenance and testing at the required regulatory intervals.
- ✅ Conduct ultrasonic level testing only within the temperature range specified by the equipment manufacturer.
- ✅ Verify the integrity and material type of bursting discs, replacing any pre-2016 copper types with approved alternatives.
- ✅ Record all maintenance and inspection results in the vessel’s Safety Equipment Logbook and Planned Maintenance System (PMS).
Final Note
Fixed CO₂ fire-extinguishing systems remain a critical barrier in onboard fire protection. Even minor deficiencies—such as inaccurate level readings or component fatigue—can have major safety consequences.
At Marine Surveyor Consultant Sagl, we continue to support ship operators with independent inspections, risk assessments, and pre-PSC audits, ensuring every vessel maintains zero-deficiency readiness in accordance with Flag, Class, and IMO standards.
