Foam Fixed Fire Fighting System In Ships With Line Diagram

         Foam fixed fire extinguishing systems are very effective and popular fixed fire fighting system in marine field. Foam gives smothering and cooling effect to the applied area. It can be used in open areas like deck as well as closed areas like engine room. Below you can see a typical line diagram of fixed foam fire fighting system.

  Foam solution itself won't make foam it requires water and air for making proper foam. The main components of foam system are,
> Foam tank
> Foam pump
> Proportioner
> Sea water pump
> Foam monitors
> Non return valve springs and isolation valves

       Must Read:> Maintenance and checks on Foam Fire Fighting System

Foam Tank 
    It's the storage tank of foam solution having a level gauge to check the level of the foam solution. There is a filling cap to refill the foam solution. Also, a vent is provided to avoid over pressurisation and under pressurisation of the tank. A drain is also provided with the help of which you can check the foam solution and drain out the whole solution if it seems to be damaged.
Foam pump 
    It's a centrifugal pump having suction from foam tank and fire line. The suction from fire line is only for flushing and testing purpose of the pump. In some systems instead of pump edectors are provided in the fire line to suck out the foam from fire line
     Improper water and foam mixture can't make a proper foam; this is done with the help of Proportioner. Water and foam mixing ratios can be adjusted using this.
Sea Water Pump 

     This may be fire pump or emergency fire pump which will give enough water in the foam line.
Foam monitors
     Mixing of air takes place in foam monitors. Foam monitors can be rotated to 360 degrees and have an elevation of -45 degree to +70 degree. 
Non return valve springs and Isolation valves
     At the suction side of the foam pump, a non return valve is provided to  avoid the contamination of foam with sea water.
     Isolation valves are provided in particular interval in the foam line to isolate the line if it got damaged during fire.

Explanation Of Working Of Above Line Diagram 
> Line up the fire pump to the foam line
> Start fire pump
> Open the suction and discharge valve of foam pump. Make sure that valves in flushing lines are closed
> Start foam pump
> Open the monitor or foam hydrant valve as required and fight the fire

Low, Medium and High expansion foam fixed fire fighting system
 > The ratio of mixing with water determines whether the foam generated is high expansion foam,medium expansion foam or low expansion foam
>Low expansion foams are using in open areas like deck because its having heavier density. If high expansion foam is used , because of low density it may get  thrown by the wind
>High expansion foams are used in closed spaces like engine room
>The foam with expansion ratio between 1:2 and 1:20 is called low expansion foam.
>Foam with expansion ratio between 1:20 and 1:200 is called medium expansion foam.
>Foam with expansion ratio above 1:200 is called high expansion foam.

Questions you can answer with this article 
>Draw and explain foam fixed fire fighting system
>Why low expansion foams are used on deck?
> What is the propotion ratio of both high expansion and low expansion fire fighting system?
> Function of proportioner
> Why isolation valves are provided in the foam line?

Please comment for mistakes and doubts


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  1. How to maintain low and high expansion foam with same proportinator?

    1. As far as I am aware you cannot use the same prop unit for Low + High Ex foam as Hi Ex is normally inducted at 2% and Low expansion at 3% / 6%
      I know there have been systems approved using a HiEx foam for both ER and Deck protection but this is not possible !!

  2. Could u pls you please tell me, Which side is engine room side and deck side of this drawing?

    1. here only deck side is shown. No engine room line is given.

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