Fire main and Sprinkler System

This article discusses the ship’s firemain and sprinkler system, including a diagram of the sprinkler system. Read until the end.

Every ship is fitted with a Firemain and Sprinkling system, which is mainly used to fight general fires that occur inside the ship. To acquire this aim, the firemain system consists of many types of machinery and equipment. Those are;

  1. Firemain and Sprinkler Pumps

The firemain and sprinkler pumps are normally located in Forward Engine Room (FER) and After Engine Rooms (AER). These pumps are normally having a high power like 80kW or the capability of pumping 80 Tons per Hour (TPH).

Usually, one 80KW pump can pressurise the system up to 7kg/cm2.

Diagram for Sprinkler System
80 TPH Fire & Sprinkler Pump

Some firemain and sprinkler system contains Diesel driven pumps to use in emergencies. A diesel-driven firemain pump is a piece of essential machinery in military vessels. Normally this pump is fitted in the Quarter Deck area (the rearmost part of the ship) because there is no machinery needed when fitted at the quarterdeck for supplying air and removing exhaust for the operation during a total power failure.

41 TPH Emergency Fire Pump
41 TPH Emergency Fire Pump

The pressurizing capability of the emergency firemain pump is a bit lower than the firemain pumps. Normally it is 41 Tons per Hour (TPH).

  1. Valves, Tubes and Branches

The pumps continuously take suction from the sea tube fitted with an angle valve and duplex strainer and discharge to the firemain line. The all-individual branches are connected to this firemain line with necessary isolating valves.

Diagram for Sprinkler System
Ship’s Firemain Pump Arrangement

Bleed lines are provided on the discharge side of the fire and sprinkling pump to pass 1% of the pump capacity overboard. The flow rate of the bleed line is regulated by an orifice plate. The butterfly valves are installed at firemain bars to allow isolation. These valves are normally kept open to ensure firemain pressure.

  1. Sprinklers & the Diagram for Sprinkler System

Sprinkler systems can be operated manually or automatically. The sprinkling system is manually operated by using valves. The automatic sprinkler system is fitted with Quartzoid bulbs sprinklers, which operate at a specific temperature (Ex: 68 degrees of Celcius +/- 2 degree) and allows the water to pass through the sprinklers.

The Diagram of the Sprinkling System of a Ship
The Diagram of the Sprinkler System of a Ship

Locations of the ship where the Sprinklers are fitted:

  1. Magazine Compartment (Armory) – In military ships only
  2. Helicopter Hangar
  3. Paint Store

The automatic sprinklers are essentially fitted in the ship’s paint store and magazine store. The reason for providing a sprinkler system to the ship’s armoury instead of a CO2 flooding system is to quickly reduce the temperature of the ammunition and other explosive materials to prevent them from exploding.

Click HERE to see the operation of a Sprinkler.

Apart from the main goal, the firemain and sprinkler system is designed to supply seawater for the following requirements:

  1. Fire Hydrants
  2. Sprinklers
  3. For emergency cooling of the gearbox of the main engine, Controllable Pitch Propeller (CPP) system and Diesel generators.
  4. Bilge Eductor (Fixed or portable)
  5. Emergency cooling of the condenser of the Air Conditioning system
  6. Emergency cooling of the condenser of the Refrigerator system
  7. Fin stabilizer hydraulic oil cooling
  8. Anchor chain washing
  9. Vacuum toilet system and STP
Fire Hydrant
Fire Hydrant

The Operating Procedure of the Firemain Pump

Start/ Stop buttons for the Firemain pumps at MCR.
Start/ Stop buttons for the Firemain pumps at MCR.
  1. Charge all lubricators with the specific lubricating medium.
  2. Check the pumping unit externally. Confirm that all pipe connections and holding-down bolts are in order.
  3. Open suction valve
  4. Close discharge valve
  5. Ensure that the pump is free to turn by hand.
  6. Check the direction of rotation by momentarily operating the motor.
  7. Start-up motor.
  8. Open discharge valve.
Valve Openers
Valve Openers

Safety Precautions to take when operating the pump

  1. Ensure proper starting procedure is followed
  2. Regulate the excess pressure in the system by opening overboard valves.

The Operating Procedure of the Firemain and Sprinkler System

  1. Check the firemain pressure available till the operating valve using the pressure gauge fitted there or through the Integrated Alarm and Machinery Control System (IAMCS).
  2. Open the isolating valve of the sprinkling system corresponding to the compartment to be sprinkled.

Safety Precautions to take when operating the system

Ensure adequate pumping out arrangement available inside the compartment. If not, prepare a suction arrangement using eductors and non-submersible, submersible pumps.

3 Phase Submersible Pump
3-Phase Submersible Pump
3-Phase Submersible Pump with its Power Supply Unit
3-Phase Submersible Pump with its Power Supply Unit
3-Phase Diesel Driven Non-Submersible Pump
3-Phase Diesel-Driven Non-Submersible Pump

Maintenance Procedure of the System

  1. All the isolating valves in the system are to be overhauled and pressure tested in every scheduled refit.
  2. The system will be flushed with fresh water after every operation or periodic test.
  3. Sprinkler nozzles are to be cleaned during every scheduled refit.
  4. System pipes are to be surveyed during the refits and renewed if required.


Firemain and sprinkler system is a ring main system. One pump can pressurize the system alone.

The normal pressure of a fire main and sprinkler system would be different from system to system but most of the systems maintain 7kg/cm2 pressure.

In ships, there are multiple fire hydrants fitted in every deck covering the entire ship. For every fire hydrant, there is a fire horse kept aside.

Except for the automatic sprinklers, the total firemain and sprinkler system is not automated. After receiving the fire alarms through the ship’s Automatic Fire Detection System, the ship’s staff initiate the extinguishing procedure using fire hydrants and hoses.

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