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Classification of the uses of pressure reducing valves and an introduction to their functions. Function of steam pressure reducing valves: The pressure after the auxiliary valve is used to regulate the opening degree of the valve element, thereby keeping the pressure behind the valve within a certain range. Cooling water is injected inside the valve or behind it to lower the temperature of the medium; such valves are known as pressure reducing valves. Pressure reducing valves work by controlling the opening degree of the valve element inside the valve in order to regulate the flow rate of the medium and reduce its pressure, with the aid of cooling mechanisms as well. The feature of this valve is that it maintains the outlet pressure and temperature within a certain range, even when the inlet pressure keeps changing. A pressure reducing valve is an essential component of pneumatic control valves; its main function is to reduce the pressure of the air supply and stabilize it at a constant level, so that the control valve can receive a stable supply of air power for regulation and control. Based on their structural design, they can be classified into film type, spring-film type, piston type, lever type, and bellows type ； Based on the number of valve seats, they can be manually classified as single-seat and double-seat types ； Based on the position of the valve disc, they can be divided into direct-acting and reverse-acting types. I. Purpose of direct-acting pressure regulators: The simplest type of pressure regulator, a direct-acting pressure regulator that features a flat diaphragm or a bellows. Since it is a standalone structure, there is no need to install external sensing wires downstream. It is the smallest in size and most cost-effective of the three pressure relief valves, designed specifically for medium to low flow rates. The accuracy of directly-acting pressure regulators is typically +/−10% of the downstream setpoint. II. Applications of piston-type pressure regulators: The piston-type pressure regulator combines two valves – a pilot valve and a main valve – into one unit. The design of the pilot valve is similar to that of a directly-acting pressure reducing valve. The exhaust pressure from the pilot valve acts on the piston, causing it to open the main valve. If the main valve is too large to be opened directly, this design uses the inlet pressure to open the main valve. Therefore, compared to directly-acting pressure regulators, piston-type pressure regulators offer higher capacity and accuracy (+/-5%) at the same pipe size. Similar to direct-acting pressure regulators, the pressure regulator senses pressure internally, eliminating the need for external sensor wires. III. Applications of diaphragm-type pressure regulators: In this type of pressure regulator, dual diaphragms replace the piston found in internal pilot-type pressure regulators. This increased diaphragm area enables the opening of a larger main valve, and at the same pipe size, it has a higher capacity than internal pilot piston pressure relief valves. Furthermore, the diaphragm is more sensitive to pressure changes, with an accuracy of +/-1%. The higher accuracy is due to the positioning of the downstream sensing wire (outside the valve), where there is less turbulence of gas or liquid. This pressure relief valve is highly flexible, allowing the use of different types of pilot valves (such as pressure valves, temperature valves, air loading valves, solenoid valves, or a combination of several such valves). Pressure relief valve installation: The pressure relief valve must be installed on a horizontal pipe with the main diaphragm chamber located below the pipe. To meet high flow rates or large variations in load, or when a backup is required, multiple valves can be used in parallel. When the pressure regulation ratio exceeds 10:1, considering the use of two valves in parallel is necessary. To avoid fluctuations, the pipe volume between valves should be at least 50 times the length of the pipe; a steam trap should be installed between the two pressure regulators to ensure adequate steam drainage. Pressure gauges should be installed upstream and downstream of the pipeline to enable the setting and monitoring of the pressure regulator. Daily maintenance of pressure regulators: We recommend disassembling the pressure regulator for a thorough cleaning every 12 or 18 months. It is necessary to remove the pressure regulator from the pipeline during repairs. The following components need to be inspected and ground, and replaced if necessary: 1. Main valve seat and valve spool ； 2. Pilot valve chamber assembly ； 3. Main valve filter screen ； 4. Main valve diaphragm ； 5. Pilot valve diaphragm. Safety tip: Be careful when handling gaskets, as stainless steel reinforcements can easily cause scratches. Working principle of the pressure reducing valves produced by Jindian Valve Co., Ltd.: http://www.jdfam.com/uploads/allimg/160706/1-160F60UI4C3.png Summary: The working principle of a pressure reducing valve is to adjust the pressure so as to reduce the inlet pressure to a desired outlet pressure; it relies on the energy of the medium itself to keep the outlet pressure stable automatically. From a fluid dynamics perspective, a pressure reducing 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 pressure reduction. Then, through the regulation of the control and adjustment system, the fluctuations in pressure behind the valve are balanced with the spring force, thereby keeping the pressure behind the valve constant within a certain error range.