Fire fighting

1. CO2 FIXED FIRE
FIGHTING SYSTEM

3. CO2 FIRE FIGHTING SYSTEM
• 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

4. • 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.

5. WHY CO2 IS USED?
• 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

6. CO2 SYSTEM WORKING
• CO2 flooding system consist of main CO2 bottles, common manifold, master
valve or distribution valve and distribution pipe lines with nozzles
• Main CO2 bottles contain carbon dioxide in liquid state with a pressure of 56 bar
at 20 degree Celsius. Pressure of CO2 at 25 and 30 degree Celsius are 64 bar and
71 bar respectively.
• So it is important to keep the temperature of CO2 bottles low for limiting the
pressure inside bottles. CO2 from the main bottle is released by a ‘CO2 release
cabinet’

7. • As soon as the release cabinet door is opened, a micro switch is activated.
• The micro switch will ensure the activation of CO2 warning alarms and ventilation
shut off.
• CO2 release cabinet or release box consist of two pilot CO2 cylinders or bottles
containing CO2 gas inside.
• The pressure of CO2 inside these pilot bottles is same as that of main CO2
bottles. Only quantity of gas is different.

8. • For releasing CO2 to the protected space, one of the pilot bottle valve is opened.
• Now CO2 reaches two valves marked 1 and 2.
• First valve 1 is to be opened.
• Then CO2 passes through a non return valve and opens pneumatically operated
master valve.
• Now master valve is opened. Next, open valve 2 in the release cabinet, which
supply CO2 to main CO2 bottle head assembly through a non return valve and
‘time delay unit’.

9. • Head assembly consist of a pressure operated cylinder valve. This pressure operated
cylinder valve prevents CO2 from bottle coming to the common manifold. As CO2
reaches the head assembly from pilot bottle, pneumatic actuator in the head moves
and opens the pressure operated cylinder valve.
• Then CO2 from main bottle escapes to the common manifold via non return valve as
shown. Each of the main CO2 cylinder have a head assembly and non return valve. The
pilot CO2 line is connected to all these heads.
• All the CO2 from the main bottles now release to common manifold. Since the master
valve is already open before, CO2 from manifold is released to the protected space
through distribution pipe lines and nozzles.

10. • As you can see in the diagram, there are two CO2 release cabinets. One is local
release cabinet and is located in the CO2 room itself. One more remote release
cabinet is used, which is located in a remote place such as fire control station.
• This facilitates operation of CO2 flooding system from a remote place other than
CO2 room. Both release cabinets are connected in parallel and non return valves
fitted in the lines prevent back flow of CO2.
• Also two pilot CO2 bottles are placed in the release cabinet. Only one is sufficient
for the operation of both master valve and CO2 bottle head assembly.

11. TIME DELAY UNIT
• CO2 from the pilot bottles in release cabinet reaches main CO2 bottle head
assembly through a time delay unit. Function of this time delay unit is to delay
the supply of CO2 to the head assembly for 60 – 90 seconds.
• In other words, when valve 2 in the release cabinet is opened, CO2 reaches only
after 60 to 90 seconds to the head assembly. Reasons for providing such a s delay
in CO2 flooding system are given below.
• As soon as CO2 release cabinet opens, alarm is sounded in the protected space. A
time delay of 60 to 90 seconds give sufficient time for any personnel in the
protected space to escape, even after the operation of both valves in the release
cabinet.

13. • The time delay can be achieved in different ways. Out of these, two types of time delay unit is
commonly used in CO2 flooding system on board ships. One is electrical type, which has an AC
220 V power supply, a pressure switch, timer and a solenoid valve as shown in the figure below:
• Power source is always available for the unit. Solenoid valve is normally in closed position. When
CO2 from pilot cylinder (CO2 release cabinet) reaches the time delay unit, the pressure acts on
the pressure switch. This closes the pressure switch.
• But the timer allows power supply to the solenoid only after 60-90 seconds, the timing can be
adjusted as required. As soon as the specified time is reached, solenoid becomes energize and
the solenoid valve will open. This allow passage of CO2 to the pressure operated cylinder valve
of main bottle. Normally a by pass valve is also fitted across this time delay unit which can be
used in case the unit goes defective.

14. THANK YOU