The hyper mist or high pressure fog fire fighting system is installed for all important ship’s machinery systems in the engine room (ME. AE, Purifier, Boiler etc.). The high-pressure water mist/fog system provides water mist protection during emergencies to engine room areas and machinery spaces. This system is independent of any other fixed fire fighting system such as foam or CO2 system.
Following are the most common areas covered by water mist system :
- Incinerator room.
- Auxiliary boiler room.
- Auxiliary generators.
- Main engine cylinder head platform.
- Purifier room.
- Inert gas generator room.
- Steering gear room.
A fresh water pump takes suction from fresh water tank to supply high-pressure water to the sprinkler system. Each area is isolated by valves, which can be opened during emergency situations involving fire. The system is kept at constant stage of readiness.
The MICROFOG Fire Extinguishing System has the following effects :
- Cooling effect (quick cooling by evaporation latent heat).
- Oxygen replacement effect (replacement of air with water vapor generated in a large quantity, and absorption of radiation heat).
- Shut-off effect (the floating fog forming walls of water).
- Smoke eliminating effect (the floating smoke particles being adsorbed and settled by the fog).
High-pressure water is injected through a special nozzle working within pressure range of 4 to 10 MPa (depending upon the design of the system), which breaks the water droplets into fine mist. The diameter of the water mist particle range from 50 to 200 µm which improves the fire extinguishing effect and efficiency of the system. The distance between any two nozzles is very critical as area covered by one nozzle must be such that no space is left unsprayed in the fire affected area.
Operating Procedure :
The system start select switch on the main control panel must always be set to AUTO & MANUAL position for automatic start. (The automatic activation with the fire alarm system is possible only in this mode.)
Starting : Automatic Start : Water mist system will be automatically released into the protected area where fire is detected by the fire alarm system (both smoke and flame detectors), and an audible and visible alarm is activated in that protected area.
Manual Start : Water mist system can be started manually from the control panel and from the local points whenever needed, independent of the fire alarm system.
The following conditions must be maintained at all times to ensure hyper mist system is on stand by for operation :
- Sufficient water level must be retained in the fresh water tank.
- Make sure the power supply is available.
- The fire alarm system must be in operation.
- Drain and test valves must be closed.
- The area around the Hyper mist water pump must be clear of any obstructions.
After confirming extinction of a fire, the water mist system can be stopped manually by cancelling the signal from the fire alarm system and pressing the STOP button on the control panel or local point.
Read more : A guide to fire pumps for ship