Water Mist Fire Fighting System
Engine room fires represent a hazard for crew members working onboard ships and heavy financial loss for the ship owners or operators. The investigation reveals that about 56% of all engine room fires were caused by the combination of oil leakage onto a hot surface. Removal of hot surfaces and correct installation of couplings and hoses in fuel oil system has reduced risk of fire significantly. In case of an engine room fire, a local water mist fire fighting or extinguishing system can be used to avoid the escalation of fire and keep the temperatures low.
System Components
- Main Control Panel
- Water Pump (For High Pressure Water)
- Fire Detectors ( Detects Fire in Protected Area)
- Solenoid Valve (One For Each Protected Area
- Water Nozzles ( Produces Water Mist)
System Description
The water mist fire fighting system basically consists of fire detection part and fire fighting part. The fire detection part monitors and detects the fire condition of the protected area. If any fire is detected, it transits the information on fire location to the main control panel.
The fire fighting part activates the pump and solenoid valve(for the protected area) and discharges the water mist through the nozzles over the protected area. The water mist fire detection and fire fighting system can be operated automatically or manually.
Automatic Operation
The water mist fire fighting system consists of two detectors placed over the area to be protected (such as main engine, auxiliary engines, incinerator, auxiliary boiler, purifiers, etc.). Out of these two detectors, one is a smoke and other is a flame detector. The figure below shows smoke, flame detector along with the water mist nozzle fitted on top of the protected area.
If only one detector is activated in a protected area, it gives a fire alarm as a pre warning. In case both the detectors are activated, the information is transmitted to the main control panel of the water mist fire extinguishing system and it starts the water pump, and opens the solenoid valve to the particular protected area. Water at high pressure (around 10 bar at the nozzle) reaches water mist nozzles and forms fine mist which is sprayed over the area under fire. Water mist is discharged until stop. If the fire is not extinguished, the water mist can be discharged during 20 minutes according to international rule regulations.
The figure below shows solenoid valves which are electrically operated by the main control panel for directing high pressure water to the nozzles placed in protected area.
Manual Operation
In case water mist is to be manually sprayed over any protected area, the ‘START’ push button on the local or remote control panel for the particular area can be activated, which will start the pump and activate the solenoid valve for the respective area.
Requirement and Rules
According to SOLAS Chapter 2-2, Regulation 10.5.6 and 1.2.2.4, new vessels constructed on or after July 1, 2002, passenger ship of 500 gross tonnages, cargo ships of 2000 gross tonnages and some existing vessels should arrange this system.
Also in IMO MSC Circular 913and 668 Appendix A, it is mentioned this system should provide localized fire suppression in are, without the necessity of engine shut down, personnel evacuation, shut down of forced ventilation fans or the sealing of the space and component manufacturing standards of equivalent water based fire extinguishing systems.
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