Difference Between Hvws And Mvws System 525v26

1.Medium velocity systems – cooling fire down Medium velocity sprayers discharge a water spray of finely divided droplets at medium velocity. They are ideal for protecting hazards involving light oils where emulsification from high velocity sprayers is not possible. The fine spray has a high heat absorption rate so medium velocity sprayers are an effective method of protecting adjacent plant and structures from heat during a fire by providing a continuous cooling spray over the exposed surfaces. Keeping nearby equipment cool minimises damage and reduces the risk of explosion. Medium velocity water spray system is designed to control fires involving the lighter oils, liquefied petroleum gases and other flammable liquids with flash points below 650 C. Cooling smothering and dilution play apart in varying degrees with such a system and a well known example of such a system is the PROTECTOSPRA SYSTEM. This type of system utilizes sprayers which produce a medium velocity water discharged with directional properties operating at a minimum water pressure of approximate 20 P.S.I. sprayers can be arranged for individual automatic operation or for automatic and manual operation in groups to command the plant or fire area concerned. Here again, the essence of the design is proper discharged pattern, careful hydraulic calculation and balance of flow and pressures. All systems are fitted with alarm equipment and monitoring devices as required. Medium velocity water spray system has been developed and extensively installed for the following applications. For fire risks involving the lighter oils, liquefied petroleum gases, and other inflammable liquids, where it may not be possible or desirable to extinguish the fire completely. For the protection of vessels, plant, and structures exposed to heat from adjacent and surrounding fires. 2.High velocity systems – getting under the fire High velocity systems are often used to protect equipment that incorporate heavy or medium oils; equipment such as transformers, circuit breakers, diesel engines and fuel oil storage tanks, turbo alternator lube oil systems and oil fired boilers. The high velocity nozzles are specifically designed to discharge a jet of water at high speed. The water jet forms a cone of coarse spray of uniform density which is discharged over a defined area. The 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 principal way the fire is extinguished, along with a cooling and smothering effect. The shape of the spray cone, the fire area ed and the water flow is all controlled by the nozzle specifications – the orifice size and the shape of the internal swirl plate – along with the water pressure and the orientation of the nozzle. High Velocity Water Spray System are installed to extinguish fires involving liquids with flash points of 650 C (1500 F) or higher. Some of the worst fires which have occurred in the history of fire fighting have been those involving oils and similar inflammable liquids. Unless promptly tackled at the source, such fires can rapidly grow to catastrophic proportions, often with irreparable damage to valuable plant.