CO2 flooding system or central bank CO2 system is one of the common fixed fire fighting system installed on most of the ships. It releases carbon dioxide (CO2) in bulk quantity to a protected space (such as engine room, cargo hold, purifier room, pump room, etc.) under fire. Smothering action of CO2 extinguishes the fire thereby preventing spreading of fire to other parts of the ship. It consist of several CO2 cylinders located in a separate room, called CO2 room. These bottles contain CO2 in liquid state. When the fire in a protected space goes out of control or in a situation when the fire is not able to extinguish by local fire fighting media, CO2 flooding system comes into picture. CO2 from the bottles directed via common manifold, main valve and distribution pipe lines to nozzles through which it is released to the protected space for fire extinction. Due to safety reasons, the CO2 flooding system is manually released from a release cabinet located outside the protected space.
Why CO2 is used?
Carbon dioxide is the fire extinguising medium used in CO2 flooding system. It is an effective fire suppression agent applicable to a wide range of fire hazards. It has a high rate of expansion which allows it to work fast. When applied to a fire, CO2 provides a heavy blanket of gas that reduces the oxygen level to a point where combustion cannot occur. Since carbon dioxide is a gas, there is no clean up associated with a system discharge. CO2, a compound of carbon and oxygen, is a colorless gas which cause coughing to occur when inhaled. At higher concentrations it is acutely toxic. Low and high pressure CO2 is used for the fire protection of machinery spaces, pump rooms, cargo holds, paint stores and galley exhaust ventilation ducts on board ships.
There are several advantages for the CO2 as a fire fighting medium. They are:
- Density is 1.5 times higher than air. So CO2 settles down and displaces air.
- It can be easily liquefied and bottled.
- 20% – 30% CO2 concentration extinguishes fire by smothering
- Non-corrosive
- Non- conductor of electricity
- No residues left after application
- No deterioration with age
Similarly there are some disadvantages also, such as:
- CO2 is highly asphyxiating. 9% concentration causes unconsciousness within minutes
- Very little cooling effect. So there is danger of re-ignition.
- When discharged, solid CO2 particles present and generate sufficient static electricity to produce spark.
Explanation of CO2 Flooding System
As mentioned earlier CO2 flooding system floods the protected space under fire with carbon dioxide, which displaces air, thereby removing one leg of fire triangle for the extinction of fire. CO2 flooding system consist of main CO2 bottles, common manifold, master valve or distribution valve and distribution pipe lines with nozzles as shown in the figure below. Click on the diagram to enlarge.
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