Solenoid valves are industrial equipment controlled by electromagnetics, and are the basic automation components used to control fluids. They belong to actuators and are not limited to hydraulic and pneumatic. Used in industrial control systems to adjust the direction, flow, speed and other parameters of the medium. The solenoid valve can be used with different circuits to achieve the desired control, and the accuracy and flexibility of the control can be guaranteed. There are many kinds of solenoid valves. Different solenoid valves play a role in different positions of the control system. The most commonly used are check valves, safety valves, directional control valves, speed regulating valves, etc.
Direct-acting solenoid valve Principle: When energized, the electromagnetic coil generates electromagnetic force to lift the closing member from the valve seat, and the valve opens; when the power is off, the electromagnetic force disappears, the spring presses the closing member on the valve seat, and the valve closes. Features: It can work normally under vacuum, negative pressure and zero pressure, but the diameter is generally not more than 25mm.
Stepped direct-acting solenoid valve Principle: It is a combination of direct-acting and pilot-operated principle. When there is no pressure difference between the inlet and the outlet, after the power is applied, the electromagnetic force directly lifts the pilot small valve and the main valve closing part in turn, and the valve opens. When the inlet and outlet reach the starting pressure difference, after the power is turned on, the electromagnetic force pilots the small valve. The pressure in the lower chamber of the main valve rises, and the pressure in the upper chamber decreases, so that the main valve is pushed upward by the pressure difference. Force or media pressure pushes the closing piece and moves down to close the valve. Features: It can operate at zero pressure difference, vacuum, high pressure, but the power is large, and it must be installed horizontally.
Pilot operated solenoid valve Principle: When power is applied, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, and a pressure difference between the upper and lower parts is formed around the closing member. The fluid pressure pushes the closing member upward and the valve opens. When the power is off, the spring force opens the pilot. The hole is closed, and the inlet pressure passes through the bypass hole to quickly form a lower and upper pressure difference around the valve closing member. The fluid pressure pushes the closing member to move downward and closes the valve. Features: The upper limit of the fluid pressure range can be arbitrarily installed (customized) but must meet the fluid pressure differential conditions.
2. The difference between the valve structure and material and the principle of the solenoid valve is divided into six sub-categories: direct-acting diaphragm structure, step-wise direct-acting diaphragm structure, pilot diaphragm structure, direct-acting piston structure, Step by step direct acting piston structure, pilot piston structure.
3. Solenoid valve is classified according to function: water solenoid valve, steam solenoid valve, refrigeration solenoid valve, low temperature solenoid valve, gas solenoid valve, fire solenoid valve, ammonia solenoid valve, gas solenoid valve, liquid solenoid valve, miniature solenoid valve, Pulse solenoid valve, hydraulic solenoid valve normally open solenoid valve, oil solenoid valve, DC solenoid valve, high pressure solenoid valve, explosion-proof solenoid valve, etc.
1. The external leakage is blocked, the internal leakage is easy to control and safe to use Internal and external leaks are a threat to safety. Other automatic control valves usually extend the valve stem, and the rotation or movement of the valve core is controlled by electric, pneumatic and hydraulic actuators. This must solve the problem of external leakage of the long-term action valve stem dynamic seal; only the solenoid valve is completed by the electromagnetic force acting on the iron core sealed in the magnetic insulation sleeve of the electric regulating valve. . Electric valve torque control is not easy, it is easy to produce internal leakage, and even break the stem head; the structure of the solenoid valve is easy to control internal leakage until it reaches zero. Therefore, the use of solenoid valves is particularly safe, especially suitable for corrosive, toxic or high and low temperature media.
2, the system is simple, it will be connected to the computer, the price is low The solenoid valve itself has a simple structure and a low price, and is easier to install and maintain than other types of actuators such as regulating valves. What is more remarkable is that the automatic control system is much simpler and the price is much lower. Since the solenoid valve is controlled by a switch signal, it is very convenient to connect with an industrial computer. In today’s era of popularization of computers and sharply lower prices, the advantages of solenoid valves are even more obvious.
3, action express, small power, lightweight The solenoid valve response time can be as short as a few milliseconds, and even pilot-operated solenoid valves can be controlled within tens of milliseconds. Due to its own circuit, it is more sensitive than other self-control valves. A properly designed solenoid valve coil consumes very low power and is an energy-saving product. It can also automatically trigger the action and maintain the valve position without power consumption. The small size of the solenoid valve saves space and is light and beautiful.
4, the adjustment accuracy is limited, the applicable medium is limited Solenoid valve usually only has two states of opening and closing. The valve core can only be at two extreme positions and cannot be adjusted continuously, so the adjustment accuracy is also limited to a certain extent. Solenoid valve has higher requirements on the cleanliness of the medium. Granular media cannot be used. If it is an impurity, it must be filtered first. In addition, viscous media cannot be used, and the viscosity range of media for specific products is relatively narrow.
5.Various models and widely used Although the solenoid valve has inherent disadvantages, its advantages are still very prominent, so it is designed into a variety of products to meet various needs and has a wide range of uses. The advancement of solenoid valve technology also revolves around how to overcome the inherent deficiencies and how to make better use of the inherent advantages.