A ship's main emergency fire system consist of a specific number of fire hydrants located at strategic positions across the ship. A series of dedicated pumps are provided to supply to these fire hydrants. The number and capacity of pumps required for a particular type of ship is decided by an international governing authority.
All these pumps are supplied power from the main power system. Apart from that, an emergency fire pump is also provided , which is located remote from the machinery space. The emergency fire pump has its own independent means of power source, which can be used to take over in case of main power failure.
Moreover, all the hydrant outlets are provided with an isolating valve so as to isolate those valves which are not in use. The fire hydrants are also provided with standard size flanges in order to attach hoses which have nozzles attached to them. All the hoses are provided with snap in connectors for easy and quick engaging and disengaging operation. The nozzles attached to the hoses are generally of two types - jet and spray , depending on the type of discharge required for extinguishing the fire. Both the nozzles can be adjusted according to the type of spray and flow required, which could be played over the fire to cool it without spreading.
The pumps are connected with the main sea water connection, having appropriate head to prevent any type of suction problem. The valves supplying water to these pumps are always kept open to provide a constant supply of sea water to fight fire at any point of time. Though sea water is the best mode of fighting fire, the main emergency fire fighting system can only be used on fires of Type A. However, in case of class B fires, if all modes for extinguishing fire fails, sea water from main emergency system can be used.