The electric valve is simply usedElectric actuator control valveTo open and close the valve.It can be divided into two parts, the upper part isElectric actuatorThe lower part is the valve.It can also be called air conditioning valve.
Electric valve isAutomatic control valveAs a high-end product, it can not only realize the switch function, but also realize the valve position adjustment function of the adjustable electric valve.The travel of electric actuator can be divided into 90 ° angle travel and straight travel. Special requirements can also meet the full travel of 180 °, 270 ° and 360 °.The angle travel electric actuator is used together with the angle travel valve to realize the valve 90 ° internal rotation to control the pipeline fluid on and off;The straight stroke electric actuator is used together with the straight stroke valve to realize the up and down movement of the valve plate to control the flow on and off of the pipeline.
Electric valves are usuallyElectric actuatorIt is connected with the valve and becomes an electric valve after installation and commissioning.The electric valve uses electric energy as power to connect the electric actuator to drive the valve, so as to realize the opening and closing and regulating actions of the valve.So as to achieve the purpose of switching or regulating the pipeline medium.[1]
The drive of the electric valve is usually driven by a motor. It takes a certain amount of time to complete the opening or closing action, so it can be adjusted.Compare withstand voltage impact.The solenoid valve is quick open and quick close, which is generally used for small flow and small pressureswitching frequency A large place;The electric valve is on the contrary.The opening of the electric valve can be controlled, with the states of open, close, half open and half close. It can control the flow of the medium in the pipeline, but the solenoid valve can not meet this requirement.[1]
The three wire electric valve has three lines F/R/N, F represents the forward action (or open action) control line, R represents the reverse action (or close action) control line, and N represents the ground wire.Solenoid valveIt is a kind of electric valve;The magnetic field generated by the solenoid coil is used to pull the valve core, so as to change the on-off of the valve body. When the coil is powered off, the valve core will return by the pressure of the spring.[1]
Basic categories
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According to the valve position function, the electric valve can be divided into: switching electric valve and regulating electric valve;According to the valve position, it can be divided into: electric ball valve and electric butterfly valve;According to the shape of valve body, it can also be divided into ordinary electric valve and micro electric valve.The electric valve is usually of on-off type, but also of regulating type, such as the fan inlet pipe regulating water flow.The on-off electric valve is generally divided into two types: normally closed and normally open. The normally closed type means that the valve is closed when power is cut off, and the normally open type means that the valve is open when power is cut off;In addition, according to the wiring, there are three wire and two wire systems. The large diameter is mostly three wire, and the small diameter will have two wire and three wire systems.[1]
major function
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Electric valve is used for analog quantity regulation of medium flow of liquid, gas and air system pipes, and it is AI feedback.Electric valves can also be used as two position switch control in the control of large valves and air systems.There can be AI feedback signals, which can be controlled by DO or AO, as can be seen in large pipelines and air valves.[1]
Equipment characteristics
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Electric valve
1. It can meet the requirements of most working conditions and working conditions that ordinary valves cannot be used;
2. It has switching and regulating functions, valve position indication and output;
3. Applicable to almost all media, with maximum viscosity of 600mmtwo/S (centis);
4. High temperature resistance, chemical corrosion resistance, wear resistance and durability, water hammer impact resistance;
5. With manual function, it can be equipped with handwheel type, and explosion-proof environment actuator can be equipped with explosion-proof type;
6. Two way circulation, simple operation, stable control and long service life.[1]
Solenoid valve and electric valve
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The control valves commonly used in engineering are mainly solenoid valves and electric valves.However, they have defects in use, such as the solenoid valve is easy to be blocked by foreign matters and has large water resistance, which must be maintained by special personnel for a long time;Although the electric valve has no water resistance, it needs necessary control circuit, so the influence of waterproof steam erosion on service life is also a major problem that puzzles the promotion.[2]
Electric valve
common problem
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Scale effect
Whether it is a solenoid valve or an electric valve, scaling will not only cause valve leakage, but even affect the normal operation of the valve in serious cases. Therefore, how to eliminate the impact of scaling has become a common concern of the industry.[3]
Poor performance of control valve
The process of solenoid valve involves a wide range, but the poor performance of control valve caused by different design actuators and use of filler materials can be summarized.[3]
The existence of dead zone in the process will make the process variable deviate from the original set point.Therefore, the output of the controller must be increased enough to overcome the dead zone, and only this corrective action will occur.[3]
Main factors affecting the dead zone:
① Friction, travel, shaft torsion, dead band of amplifier.Various control valves are different in sensitivity to friction. For example, rotary valves are very sensitive to friction caused by high seat load, so pay attention to this when using.However, for some seal types, the high seat load is necessary to obtain the closing level.,In this way, the design of this valve is very poor, and it is easy to cause a large dead zone, which has an obvious and decisive impact on the process deviation.[3]
② Wear.It is inevitable that the valve will be worn during normal use, but the wear of the lubricating layer is the most serious. According to the experiment, the lubricating rotary valve has only undergone hundreds of cycles, and the lubricating layer can be used almost with a brush.In addition, the load caused by pressure will also lead to the wear of the sealing layer, which is the main factor leading to the increase of friction.The result is that the performance of the control valve is destroyed[3]
③ The friction of packing is the main source of friction of control valve. The friction caused by different packing is very different.[3]
④ Different types of actuators also have a fundamental impact on friction. Generally speaking, spring diaphragm actuators are better than piston actuators.[3]
application area
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The application fields of electric valves include: can/bottle system, beer brewing and beverage technology chemical industry, fluid mixing device, food industry concrete and cement industry, vacuum technology, water treatment device, pneumatic device, laundry room, medical equipment, boiler water supply, process control and other fields.[3]
