Medium Velocity Water Spray or MVWS System for Fire Protection
Power Plant Fire Protection System (Part-III of III)This section comprises of water based fire protection system which comprises of Medium velocity water spray (MVWS) system in thermal power plants.
Representation of MVWS Protection System
MVWS System ApplicationsMedium velocity water spray system shall be designed to protect the following:
- Cable gallery and cable spreader room in the main plant area
- ESP control room
- Switch yard room
- Ash handling plant area
- Coal handling plant area
- Water treatment plant area
- Circulating water pump area
- Sea water intake area
- Fuel oil pump house
- Switch yard and control room building
- All coal conveyor gallery in tunnels/underground and above ground
- Coal transfer points and junction towers
- Crusher house
- Emergency DG Building
- Fuel oil pump house (loading and unloading areas)
- Fuel oil storage tanks
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MVWS System Design RequirementsMedium velocity water spray system design requirements MVWS system shall be designed as per TAC regulations. The medium velocity spray system shall consists of a network of open spray nozzles fitted with a special deflector to give required angle of discharge for the water around the area mentioned above. The sprayers shall discharge a cone of water spray consisting of medium size droplets of water. The water supply to the MVWS system shall consists of a network of open spray nozzles fitted with a special deflector to give required angle of discharge for the water around the area to be protected. The water supply to the MVWS system shall be controlled by a deluge valve which shall operate electrically actuated solenoid valve on release of water pressure.
In order to avoid total flooding of the entire area of cable gallery/ coal conveyor system, the area to be protected by shall be divided into number of zones. Each zone shall have separate water supply network controlled by a deluge valve. A fire detection system provided for the MVWS protected area shall sense fire and shall actuate the deluge valve. In the event of fire in one zone, the deluge valve of the corresponding zone and those of adjacent zones on either side shall be opened.
MVWS System for Cable Galleries The cable galleries shall have number of rows of cable trays and each row will have number of tiers of cable trays. Each of the cable rows shall be provided with a network of water distribution piping and nozzles. The distribution network shall consist of distribution header for each row of cable tray and on these headers drop pipes shall be provided so as to cover all the tires. In case of fire in the cable gallery, addressable multi-sensor detector supplemented with linear heat sensing cable of digital type shall be used for detection of fire. Upon detection of fire MVW spray system shall be brought into operation by automatically opening of deluge valve, which shall allow the projectors located in that area to direct water in the form of spray, which which will cut of oxygen supply and extinguish the fire. As per TAC regulations the density of spray water system in cable galleries shall be 12.2 lpm/m2 of the surface area for spray system. The pressure at the hydraulically most remote projector in the network shall not be less than 2.8 bar.