A pressure reducing valve is a specialized device designed to automatically lower the working pressure within a pipeline. It ensures that the higher water pressure on the upstream side of the valve is reduced to a suitable level for the downstream system. These valves are commonly used in high-rise buildings, municipal water supply networks, areas with high water pressure, and mining operations to maintain optimal service pressure and flow in the water distribution system. Since the rate of water leakage and wastage is closely related to the pressure in the system, pressure reducing valves not only improve the overall efficiency of the system but also contribute significantly to water conservation. According to statistical data, they can save up to 30% of water usage.
There are various types of pressure reducing valves available, such as diaphragm type, internal spring piston type, and others. The basic principle involves using local resistance within the valve to reduce the water pressure. The pressure difference across the diaphragm or piston controls the degree of pressure drop automatically. In recent years, new designs like fixed ratio pressure reducing valves have emerged. As shown in Figure 14.2-2, these valves operate by controlling the pressure ratio through a floating piston inside the valve body. The pressure reduction ratio between the inlet and outlet is inversely proportional to the area ratio of the piston on each side. This design allows for smooth operation without vibration, eliminates the need for springs (thus avoiding issues like corrosion and fatigue), and provides excellent sealing performance, preventing leaks whether water is flowing or static. Additionally, the pressure reduction process does not interfere with the water flow.
Pressure reducing valves come in different sizes, typically ranging from DN50 to DN100. The operating pressures before and after the valve are usually less than 1 MPa and between 0.1 to 0.5 MPa, respectively, with a pressure adjustment error of ±5% to 10%.
It's important to note that although there is some head loss associated with the flow through the pressure reducing valve, the overall system benefits from reduced water waste, improved flow distribution, and better system performance, making it an energy-efficient solution in most cases.
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