Water Spray System is a special fixed pipe system connected to a reliable source of pressurized water supply and equipped with water spray nozzles for application on area / equipment to be protected. The system can be operated automatically by connection to an automatic detection and alarm system or manually, or both.
Water spray nozzle systems are generally used for fire protection of flammable liquid and gas storage tanks, piping, pumping equipment, electrical equipment such as transformers, oil switches, rotating electrical machinery etc. and for protection of openings in fire walls and floors.
The piping system is connected to the water supply through an automatically actuated Deluge Valve, which initiates flow of water. Automatic actuation is achieved by operation of automatic detecting equipment installed along with water spray nozzles. There are two types of systems namely High Velocity and Medium Velocity systems.
Types of Water Spray Nozzles & Selection
NewAge® Medium Velocity Water Spray Nozzle is an open orifice, directional spray nozzle, designed for use in water spray fixed systems for fire protection applications. NewAge® MV nozzle comes in various materials of construction and is UL Listed. MV nozzle has an external deflector that discharges a uniformly filled cone of medium velocity water droplets. MV nozzles are used to provide cooling and/or control the burning in many large scale industrial applications, such as in thermal power plants. MV nozzles are best suited for protecting hazards involving light oils – where emulsification from high-velocity water sprayers (HV nozzles) is not possible. When a fire occurs in another area of the plant, medium velocity sprayers are an effective method of protecting nearby structures from heat during a fire by providing a continuous cooling spray over the exposed surfaces.
NewAge® High Velocity Water Spray Nozzle is an open orifice and non-automatic directional spray nozzle. HV nozzle is designed for use in fixed water spray fire protection systems where a high velocity water application is needed. This includes applications such as protection of electrical transformers, circuit breakers, oil-fired boilers and lube oil systems. HV nozzle comes in various materials of construction and is UL Listed. NewAge® HV nozzles are often used to protect equipment that incorporates heavy or medium oils. Equipment such as oil type circuit breakers and transformers, diesel engines and fuel oil storage tanks, turboalternator lube oil systems, and oil-fired boilers. The high-velocity discharge water jet forms a cone of coarse spray of uniform density. This coarse spray is able to penetrate the flame zone and reach the surface of the burning oil. The turbulence created by the high velocity spray forms an oil-in-water emulsion on the surface of the oil that will not burn. This “emulsification” is the main way the fire is extinguished – along with the cooling and smothering effect.
Main Difference between MV and HV Spray Nozzle Systems
- Medium-velocity water spray systems are designed to control fires involving lighter oils, liquefied petroleum gases, and other flammable liquids with flash points typically below 65 degree C.
- High-velocity water spray systems are installed to extinguish fires involving heavy or medium oils, and other flammable liquids with flash points typically above 65 degree C.
Operation of Water Spray Nozzles
The high / medium velocity water spray system protection operates on the same principle as a deluge system. Deluge Valve is known as a system control valve in a deluge system, used for fast application of water in a spray system. Deluge valve is a quick release, hydraulically operated diaphragm valve. It has three chambers, isolated from each other by the diaphragm operated clapper and seat seal. While in ‘SET’ position, water pressure is transmitted through an external bypass check valve and restriction orifice from the system supply side to the top chamber, so that supply pressure in the top chamber acts across the diaphragm operated clapper which holds the seat against the inlet supply pressure because of differential pressure design. On detection of fire the top chamber is vented to atmosphere through the outlet port via opened actuation device(s). The top chamber pressure cannot be replenished through the restricted inlet port, thus it reaches less than half the supply pressure instantaneously and the upward force of the supply pressure lifts the clapper allowing water to enter the system piping network and alarm devices. This allows the water to flow out through the projectors in the form of high / medium velocity water spray and extinguishes the fire. Generally, a water motor operated gong (as in the case of sprinkler systems) sounds the fire alarm. Sometimes, additionally an electrical alarm may also be provided. The water spray systems should have isolation facilities so as to enable periodic testing, maintenance etc. Normally, all cut-off valves should be locked open.
Advantages of Water Spray Systems
- Extinguishes fires quickly and prevents fires from spreading over a large area
- Minimizes the damage caused by fire and reduces downtimes
- High flexibility in design and implementation
- Reduces fumes and binds contaminants
- Allows large open areas and thus a more flexible use of the premises
- Uses water, a natural fire extinguishing agent that is available in unlimited quantities at a very low price