MULTIPLE BOTTLE FIXED CO2 FIRE FIGHTING SYSTEM

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Medium for fixed gas fire fighting systems can be CO₂, steam, products of combustion of fuel. Halogen installations are now prohibited and all existing installations must have been decommissioned.

CO₂ is the most popular choice and can be used for the protection of both machinery and cargo spaces. The application technique differs for machinery spaces and cargo spaces.

The CO₂ storage system is sized to give a suitable percentage by volume in the largest protected space. Any air receivers that are capable of venting into the protected space have their volume, at standard atmospheric conditions, added to the gross volume of the protected space.

An automatically operated audible warning must be given for at least 20s before the release of CO₂.

There must be suitable provision to prevent accidental release – isolating valves and alarms.

Pipe work passing through accommodation spaces must be fully welded and is not allowed to pass through refrigerated spaces.

Release controls must be readily accessible and grouped together in as few locations as possible. Positions must not be cut off by fire in protected space. Clear instructions must be posted at each release position.

Two separate controls are required, one for opening the isolating valve, one for activating the CO₂ release.

Quantity of CO₂ required.

a)                  Cargo spaces require 30% of the gross volume of the largest protected space.

b)                  Machinery spaces require;

i)                    40% of the gross volume of the space, excluding casings.

ii)                  35% of the gross volume of the space including the casings.

The total quantity of gas required is the largest of a), b)i or b)ii.

Gas is released at a Slow Rate into the cargo spaces, with the entry at the top. The initial charge and the back up charge are determined for each individual ship and specifically written instructions are issued. Over pressurising must be avoided.

For the machinery space the gas is released at a Fast rate, 85% of the total charge within 2 mins.

This rate of discharge ensures that the CO₂ is distributed throughout the entire engine room.

Multi-bottle CO₂ system

Means must be provided for determining the total content of CO₂, either by weight (most accurate but time consuming) or by level detection (ultra-sonic, radio-active isotope).

Alarms fitted for leakage detection – connected to engine room alarm panel, and door open – release pending – dedicated CO₂ audible and visual alarm within protected space.

All lines should be blown through periodically and verified at delivery nozzles.

Bottles are tested to 228 bar, bursting discs rupture at approx. 177 bar (a temperature of about 63°C).