Marine safety service
CO2 System Servicing
Inspection, weighing, release testing and cylinder hydrostatic testing of fixed high and low-pressure CO2 fire-extinguishing systems to MSC.1/Circ.1318/Rev.1.
Overview
Fixed CO2 fire-extinguishing system servicing
CO2 system servicing is the periodic inspection, weighing, testing and maintenance of fixed carbon dioxide fire-extinguishing systems, which protect engine rooms, cargo holds, pump rooms, paint lockers, emergency generator rooms and other enclosed spaces on many ships. CO2 puts out a fire by reducing oxygen in the space, which also makes it lethal to anyone inside. A reliable system therefore has to discharge when needed, and never by accident.
vslSafety arranges a service provider with trained CO2 technicians, weighing equipment and test cylinders at the vessel’s port. Other gas agents such as inert gas and clean agents are covered under fire suppression systems.
Regulatory requirements and standards
- SOLAS chapter II-2, regulation 10, sets where fixed gas systems are required, and regulation 14 requires them to be kept in good working order.
- FSS Code chapter 5 sets the specification. For machinery spaces, the quantity must be at least 40% of the gross volume of the largest protected space (excluding part of the casing) or 35% including the casing, and 85% of the gas must be dischargeable within 2 minutes. Cargo spaces normally need 30% of the largest hold. Spaces where people work need two separate release controls and a pre-discharge alarm of at least 20 seconds. Means must be provided for the crew to check the quantity safely, such as weighing bars above each row of cylinders.
- MSC.1/Circ.1318/Rev.1 (25 May 2021), Revised guidelines for the maintenance and inspections of fixed carbon dioxide fire-extinguishing systems, which clarified the hydrostatic testing regime for high-pressure cylinders and superseded the original circular.
The circular allows some tasks to be performed by competent crew, while the release system tests at the survey interval should be carried out by service technicians or specialists trained to standards accepted by the administration. Many flags and class societies require an approved service company for weighing, release testing and cylinder testing. Some flags apply their own tolerances. For example, the Marshall Islands applies a 95% charge limit for high-pressure fixed gas cylinders, where the CO2 circular uses 90%. Check the flag circular.
Inspection and servicing intervals
| Item | Requirement | Interval | Reference |
|---|---|---|---|
| Whole system | General visual check: stop valves closed, releases accessible, piping and cylinders secure, alarms intact | Monthly | MSC.1/Circ.1318/Rev.1 |
| Low-pressure tank | Pressure gauge, liquid level, main and vapour valves secured open | Monthly | MSC.1/Circ.1318/Rev.1 |
| Space boundaries, cylinders, piping, nozzles, signs | Annual inspection | Annual | MSC.1/Circ.1318/Rev.1 |
| Cylinder contents | Weigh or verify; refill if below 90% of nominal charge; check tank level | 2 years ±3 months (passenger ships); each intermediate, periodical or renewal survey (cargo ships) | MSC.1/Circ.1318/Rev.1 |
| Discharge piping and nozzles | Blow through with dry air or nitrogen | As above | MSC.1/Circ.1318/Rev.1 |
| Activating heads, pilot lines, release cables, time delays | Function and pressure test by trained technicians | 2 years ±3 months (passenger ships); each renewal survey (cargo ships) | MSC.1/Circ.1318/Rev.1 |
| Control valves | Internal inspection | 5 years | MSC.1/Circ.1318/Rev.1 |
| High-pressure cylinders | Hydrostatic test of at least 10% (50%, then all if failures); all cylinders before the 20-year anniversary and every 10 years after | 10 years | MSC.1/Circ.1318/Rev.1 |
| Flexible hoses | Replace | Per maker, not exceeding 10 years | MSC.1/Circ.1318/Rev.1 |
What the service includes
- Safety plan, headcount and communication with the duty crew, with directional valves and main valve locked or operating arms removed before work starts
- Weighing of main and pilot cylinders, or liquid level measurement, against stamped tare and nominal charge
- Inspection of cylinder valves, clamps, manifold, check valves and flexible hoses
- Pressure and leak testing of pilot lines and servo tubing from each release station
- Function testing of activating heads, main and distribution valves, time delays and pull cables and pulleys
- Testing of audible and visual pre-discharge alarms and fan stops
- Blowing through of distribution lines and nozzles with dry air or nitrogen
- Low-pressure tank checks: level indicator, safety valves, insulation, refrigeration units and alarms
- Reconnection, return to service and fitting of dated inspection tags
Equipment and system types covered
Providers work on high-pressure cylinder banks with pneumatic, cable or electrical release and on low-pressure refrigerated tank systems used on larger ships. Common makers include Kidde, Minimax, Danfoss Semco, Tyco and Wormald, as well as many Korean, Chinese and Japanese makes fitted by shipyards.
Common defects and PSC deficiencies
- Cylinders overdue for hydrostatic testing, or no record of test dates
- Cylinders below the minimum charge, or pilot cylinders empty
- Flexible hoses older than ten years or disconnected after previous servicing
- Release cables and pulleys seized, or excessive cable travel
- Pre-discharge alarm or fan stop not working
- CO2 room used as a store, poorly ventilated or without its warning signs
Certificates and documents you receive
- Service certificate and report following the service chart format in MSC.1/Circ.1318/Rev.1
- Weighing list for each cylinder, with serial number, tare, gross and net weight
- Hydrostatic test certificates for cylinders tested, with new test date stamped
- Defect list and confirmation that the system has been returned to service
How to prepare the vessel
Send the system drawing, number and size of cylinders, and the oldest cylinder test date. The chief engineer should agree the work plan, since release tests need the system disconnected and locked, and all personnel must be informed before work begins. Keep the protected spaces covered. When cylinders are landed for testing, MSC.1/Circ.1318/Rev.1 expects them to be replaced so the required quantity remains on board. Arrange a route to land cylinders.
Information needed for a quotation
- Vessel name, IMO number, flag, class and ship type
- Port, ETA and ETD
- System maker, high-pressure or low-pressure, and protected spaces
- Number and size of main and pilot cylinders, or tank capacity
- Oldest cylinder test stamp date and last hose renewal date
- Last service date and next survey due
- Whether hydrostatic testing, refilling or hose replacement is required
vslSafety coordinates a suitable provider at the vessel’s port. Cylinder testing and refilling can be arranged through cylinder hydrostatic testing and recharging, and hold detection checked through fire detection and alarm systems.
Frequently asked questions
How often must CO2 cylinders be hydrostatically tested?
Under MSC.1/Circ.1318/Rev.1, high-pressure cylinders are subject to periodic tests at intervals not exceeding ten years. At the ten-year inspection, at least 10% are internally inspected and hydrostatically tested. If one fails, 50% are tested, and if more fail, all are tested. Before the 20-year anniversary and every ten years after, all cylinders should be tested.
How often must a CO2 system be weighed?
For cargo ships, the circular recommends weighing, or verification by other reliable means, at each intermediate, periodical or renewal survey. For passenger ships it is every two years plus or minus three months. Cylinders below 90% of the nominal charge should be refilled, although some flag administrations apply a stricter limit.
Can the crew carry out CO2 system maintenance?
Competent crew can carry out the monthly and annual inspections. The release system tests at the survey interval should be done by service technicians trained to standards accepted by the administration, and many flags and class societies expect an approved service company for weighing and cylinder testing, so check before planning crew-only work.
How long do CO2 flexible hoses last?
MSC.1/Circ.1318/Rev.1 requires flexible hoses to be replaced at the interval recommended by the manufacturer, and in any case not exceeding ten years. Hoses should be replaced sooner if damaged, kinked or corroded, and the renewal date recorded on the service chart so that the next replacement can be planned in advance.
Is it safe to service a CO2 system with the crew on board?
Yes, provided the safety measures in the circular are followed. Before any work, a safety plan should account for all personnel and set up communication between the technicians and the duty crew. Directional valves or the system block valve should be locked, or operating arms removed, to prevent accidental discharge. All personnel should be told before work begins.
