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Knowledge on solenoid valve selection. Everyone, please continue to provide suggestions for replacement. Guidelines for selection: When selecting solenoid valves, one should follow four principles—safety, reliability, suitability, and cost-effectiveness—and consider six aspects of the actual operating conditions (pipeline parameters, medium parameters, pressure parameters, power supply parameters, operation mode, and special requirements). Selection principles: Safety: That is, when making a selection, priority should be given to the safety of lives and property, especially in flammable and explosive environments! I. Reliability: Electromagnetic valves that do not function properly can damage other components of the system! II. Applicability: It is essential to consult experts when selecting a valve; for example, using a low-temperature valve for steam is a waste of money! III. Economical efficiency: This means that when low-temperature media are used, there is no need to opt for high-temperature options, as the cost of high temperatures is high! Selection criteria: First, the solenoid valve is selected based on pipeline parameters: diameter size (i.e., DN) and connection type. 1. The simplest way to determine the diameter size is to use the inner diameter of the pipeline in place. Alternatively, it can be determined by comparing the flow rate of the medium in the pipes on site with the Kv value of our company’s solenoid valves. 2. For the interface type, flange interfaces are generally required for DN50 and above, while those with DN50 or less can be chosen freely by the user. II. Selection of solenoid valves based on medium parameters: material, temperature range. 1. For corrosive media: plastic solenoid valves and those made entirely of stainless steel are recommended ； For highly corrosive media, an isolated diaphragm type must be used, such as OK69. In neutral media, solenoid valves with copper alloy as the valve body material are also a good choice; otherwise, rust particles often fall off from the valve body, especially in situations where the valve is not used frequently. Copper materials cannot be used for ammonia valves. For use in wine-making and milk processing pipelines, solenoid valves made of food-grade stainless steel should be employed. 2. High-temperature medium: The medium temperature should be within the range permitted by the solenoid valve. For applications involving hot water, steam, or heat transfer oil, it is necessary to use electromagnetic coils and sealing materials that can withstand high temperatures, as well as piston-type structures. For example, for steam at 200°C, stainless steel materials from the OK72 or OK87 series should be used; copper materials are not suitable in this case, as when the temperature exceeds 170°C, the expansion coefficient of copper conflicts with the tolerances between the piston components of the solenoid valve and its piston chamber, resulting in malfunction. 3. Medium state: It can be gaseous, liquid, or in a mixed state; different types of solenoid valves must be selected accordingly for use with gases or liquids. The state of the medium should be specified, as otherwise it will affect the stability of the valve’s performance. 4. Medium viscosity: It can generally be chosen arbitrarily as long as it is below 50 cSt; if it exceeds this value, a high-viscosity solenoid valve should be used. 5. Medium cleanliness: If the medium contains only a small amount of fine impurities, a diaphragm-type structure can be used; however, if the impurities are larger in size and more abundant, a filter should be installed before the solenoid valve at www.huaguangv.com. III. Selection of solenoid valves based on pressure parameters: principles and structural types 1. Nominal pressure: This parameter has the same meaning as that of other common valves, and it is determined according to the nominal pressure of the pipeline. 2. Operating pressure difference: For values less than or equal to zero, a direct-acting or step-direct-acting type must be used. An indirect pilot type can be selected when the minimum operating pressure difference is above 0.04 Mpa ； Vacuum solenoid valves should be used for vacuuming or siphoning pipelines. 3. Pressure range: It should fall within the allowable range of the solenoid valve; generally, when the operating pressure is greater than 1 Mpa, a piston-type structure is preferred due to its reliability and durability. For pressures below 1.0 Mpa, using a diaphragm structure is more cost-effective. IV. Power supply voltage selection: 1. Depending on the type of power supply, AC or DC solenoid valves should be selected accordingly. Generally, AC power is easy to obtain. 2. For voltage specifications, AC220V and DC24V should be given priority whenever possible. 3. For power supply voltage fluctuations, +%10% to -15% is typical for AC supplies, while ±10% is acceptable for DC supplies. If these limits are exceeded, voltage stabilization measures must be taken or special ordering requirements should be specified. 4. The rated current and power consumption should be selected based on the power supply capacity. It should be noted that the VA value is high during start-up under communication conditions; indirect-acting solenoid valves should be given priority when capacity is insufficient. V. Selection based on operating time: normally closed, normally open, or capable of remaining powered on. 1. Solenoid valves operate by utilizing the magnetic field generated when an electromagnetic coil is powered; therefore, they have only two states: closed (in a closed state when not powered) and open (in an open state when not powered). 2. If the solenoid valve is required to operate in a continuous cycle of opening and closing, an normally open type should be chosen if the time it remains open is longer than the time it remains closed; otherwise, a normally closed type should be selected. However, for some applications related to safety protection, such as fuel control and flame monitoring in furnaces and kilns, normally open valves cannot be used; because if a fault occurs and it is necessary to shut down the solenoid valve urgently, and at the same time the control instruments or power supply fail, that could lead to disaster ； To this end, after years of trial production, our company successfully introduced the OK87 and OK58 series of solenoid valves in 2003, filling a gap in the domestic market. Utilizing high-tech integration technology, these valves can remain powered on for extended periods with low coil temperature rise. VI. Select auxiliary functions based on environmental requirements: explosion-proof, fog-proof, water spray-proof, submersion-proof, ultra-low temperature. 1. Explosive environments: Electromagnetic valves with the appropriate explosion-proof rating must be used. 2. Waterproof and dust-proof models should be selected for outdoor installations or environments with high dust levels. 3. Submersible solenoid valves must be used for fountains. 4. Ultra-low temperature media or ultra-low temperature environments require low-temperature solenoid valves. It should be noted to all users that cost-effectiveness is not merely related to the price of a product; rather, its functions and quality, as well as the costs associated with installation, maintenance, and other accessories, should be given priority consideration. Moreover, the cost of a solenoid valve in the entire automatic control system, and even within the production line, is minimal; choosing the wrong one in an attempt to save a little money can result in significant damage. In short, cost-effectiveness refers not only to the product price, but also to the performance-to-price ratio and the overall cost-to-price ratio of the product.