Valve through the adjustment will be reduced to a desired inlet pressure outlet pressure, and rely on the energy of the medium itself, so that automatically maintain a stable outlet pressure valve. Fluid mechanics point of view, the valve is a local resistance can change throttle components, namely, by changing the cutting area, the flow rate and fluid kinetic energy changes, resulting in different pressure loss, so as to achieve the purpose of decompression. And then rely on the regulation of control and regulation system, the valve after the pressure fluctuations and the spring force balance, the pressure valve in a certain range of error remains constant. Valve is an automatic reduction pipeline working pressure of a special device, it can be a high pressure pipe before the valve to the valve after the piping to reduce the required level. Valves are widely used in high-rise building, urban water supply network of high pressure areas, mines and other occasions, to ensure water supply system in each point of access to appropriate services, water pressure and flow. Given the rate of water leakage and waste of water supply system, water pressure is almost the same size is proportional to valve system with improved operating conditions and potential water-saving effect, according to statistics about 30% of its water-saving effect. The construction of many types of valves, in the past are common membrane, inner spring piston and so on. The basic principle is to valve by valve flow to reduce local resistance to the flow of water pressure, water pressure drop range from film to connect the valve or piston on both sides of the import and export automatically adjust the water pressure. Since 2007 and some new valves, pressure reducing valves, such as fixed ratio. Decompression is the use of fixed than floating piston in the hydraulic valve body than the control, import and export and import side than the end of decompression piston area ratio is inversely proportional. Such valves work smoothly without vibration; valve body is no spring, so no spring corrosion, metal fatigue failure of consideration; seal leakage performance is not good, and therefore reduce both the dynamic pressure (water flow) and reduced static pressure (flow 0); especially in the decompression at the same time does not affect the water flow. 
 DN15 ~ DN100 valve usually has a variety of specifications, the valve before and after the working pressure was <1MPa and 0.1 ~ 0.5MPa, pressure range error of ± 5% ~ 10%. 
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