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01 Working principle of pressure relief valves 1) From a fluid dynamics perspective, a pressure relief valve is a throttling element whose local resistance can be varied; by changing the throttling area, the flow velocity and the kinetic energy of the fluid are altered, resulting in different pressure losses and thus achieving the purpose of reducing pressure. It relies on the regulation of the control and adjustment system to balance the fluctuations in pressure behind the valve with the spring force, thereby keeping the pressure behind the valve constant within a certain error range. 2) The pressure reducing valve can reduce the high liquid pressure in the pipeline before the valve to the level required in the pipeline after the valve; its primary medium of transmission is water. Pressure relief valves are widely used in high-rise buildings, areas with excessively high water pressure in urban water supply networks, mines, and other settings, to ensure that all water usage points in the supply system receive an appropriate water pressure and flow rate. Given that the rate of water loss and waste is almost directly proportional to the water pressure in the supply system, pressure reducing valves can improve the operating conditions of the system and help save water; statistics show that their water-saving effect is approximately 30%. 3) The working principle of a pressure reducing valve is to regulate the inlet pressure to a desired outlet pressure, and by relying on the energy of the medium itself, to maintain the outlet pressure stable automatically. 02 What are the precautions for installing a pressure relief valve? 1) For ease of operation and maintenance, pressure relief valves should generally be installed vertically on horizontal pipes. When installing a pressure relief valve, it must be installed strictly in accordance with the direction indicated by the arrow on the valve body, ensuring that it is aligned with the flow direction of the fluid. If the water quality is poor and contains impurities, a filter must be installed at the water inlet upstream of the pressure reducing valve to prevent it from affecting the proper operation of the valve. 2) To prevent overpressure behind the valve, a pressure reducing valve should be installed at a distance of not less than 4 meters from the valve outlet. The pressure reducing valve serves as a kind of check valve in the pipeline. To prevent the damage caused by water hammer, a small expansion tank can also be installed to protect the pipes and valves. The filter must be installed before the inlet pipe of the pressure reducing valve, while the expansion tank must be installed after its outlet pipe. 3) If it is necessary to install a pressure reducing valve in a hot water system, you must install a check valve between the pressure reducing valve and the expansion tank. This allows the expansion tank to absorb the increased volume of water resulting from thermal expansion, while also preventing backflow of hot water or pressure fluctuations from affecting the pressure relief valve, thus ensuring its proper operation over the long term.