Solenoid Valve Technology And Application

Solenoid valve is an industrial equipment controlled by electromagnetic. It is an automation basic component used to control fluid. It belongs to actuator and is 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 cooperate 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 ones are check valves, safety valves, directional control valves, speed control valves, etc.

Working principle of solenoid valve:

There is a closed cavity in the solenoid valve with through holes at different positions. Each hole is connected to a different oil pipe. In the middle of the cavity is a piston. There are two electromagnets on both sides. Which side of the magnet coil will be attracted to the valve body when it is energized. On the other hand, by controlling the movement of the valve body to open or close the different oil discharge holes, and the oil inlet is normally open, the hydraulic oil will enter the different oil discharge pipes, and then the piston of the cylinder is pushed by the oil pressure. Drive the piston rod, and the piston rod drives the mechanical device. In this way, the mechanical movement is controlled by controlling the current on and off of the electromagnet.

Solenoid valve classification:

(1) Direct-acting solenoid valve:
Principle: When energized, the solenoid 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, and 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 generally does not exceed 25mm.
(2) Step-by-step direct-acting solenoid valve:
Principle: It is a principle that combines direct action and pilot type. When there is no pressure difference between the inlet and the outlet, the electromagnetic force directly lifts the pilot small valve and the main valve closing member upwards in turn, and the valve opens. When the inlet and outlet reach the starting pressure difference, after power 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 drops, so that the pressure difference pushes the main valve upward; when the power is off, the pilot valve uses a spring The force or medium pressure pushes the closing piece and moves downward to close the valve.
Features: It can be operated under zero pressure difference or vacuum and high pressure, but the power is large, and it must be installed horizontally.
(3) Pilot solenoid valve:
Principle: When energized, electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, and a high pressure difference is formed around the closing member. The fluid pressure pushes the closing member to move upward and the valve opens; when the power is off, the spring force controls 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 close the valve.
(4) Stainless steel solenoid valve: It is the most common solenoid valve product. The stainless steel material is most popular with users because of its good quality and stable work. The electromagnetic valve
*This series of products are widely used in production and scientific research departments such as textiles, printing, chemicals, plastics, rubber, pharmaceuticals, food, building materials, machinery, electrical appliances, and surface treatment, as well as in people’s daily life facilities such as bathrooms, canteens, and air conditioners.
(5) Brass solenoid valve: Some users who are not demanding will choose brass solenoid valve products. The price of such solenoid valve products is relatively low and suitable for ordinary working environments.
* This series of products are generally suitable for liquid, water, gas, hot water, oil, gas and other media.
(6) Plastic solenoid valve: In some special workplaces and solenoid valves used in special media, such as the working environment with acid and alkaline media, solenoid valves made of brass and stainless steel are easily corroded, so special The plastic solenoid valve made of material (engineering plastic PVC, CPVC, UPVC, ABS or PTFE, etc.) is particularly excellent in corrosion resistance.
* This series of products are suitable for drinking water, all kinds of untreated sewage, rainwater, sea water and various acid-base salt solutions, organic solvents, etc.

Common failures of solenoid valves

The solenoid valve is composed of a solenoid coil and a magnetic core, and is a valve body containing one or more holes. When the coil is energized or de-energized, the operation of the magnetic core will cause the fluid to pass through the valve body or be cut off to achieve the purpose of changing the direction of the fluid. The electromagnetic part of the solenoid valve is composed of fixed iron core, movable iron core, coil and other parts; the valve body part is composed of spool valve core, spool valve sleeve, spring base and so on. The solenoid coil is directly installed on the valve body, and the valve body is enclosed in a sealed tube, forming a simple and compact combination. The solenoid valves commonly used in our production include two-position three-way, two-position four-way, two-position five-way, etc. Let me first talk about the meaning of the two positions: for the solenoid valve, it is electrified and de-energized, and for the controlled valve, it is open and closed.
The fault of the solenoid valve will directly affect the action of the switching valve and the regulating valve. The common fault is that the solenoid valve does not operate, which should be investigated from the following aspects:
1. The solenoid valve terminal is loose or the thread is off, the solenoid valve must not be energized, and the thread can be tightened.
2. The solenoid valve coil is burnt out. You can remove the solenoid valve’s wiring and measure with a multimeter. If it is open, the solenoid valve coil will burn out. The reason is that the coil is damp, causing poor insulation and magnetic leakage, causing excessive current in the coil and burning. Therefore, it is necessary to prevent rainwater from entering the solenoid valve. In addition, if the spring is too hard, the reaction force is too large, the number of turns of the coil is too few, and the suction force is not enough to cause the coil to burn out. For emergency treatment, the manual button on the coil can be turned from the “0” position to the “1” position during normal operation to open the valve.
3. Solenoid valve jam: the matching clearance between the solenoid valve slide valve sleeve and the valve core is very small (less than 0.008mm), and it is generally a single-piece assembly. When mechanical impurities are brought in or there is too little lubricating oil, it is easy to jam . The treatment method can be made by inserting a steel wire through a small hole in the head to make it spring back. The fundamental solution is to remove the solenoid valve, take out the valve core and valve core sleeve, and clean it with CCI4 to make the valve core move flexibly in the valve sleeve. When disassembling, pay attention to the assembly sequence of the components and the position of the external wiring, so that the reassembly and wiring are correct, and check whether the oil spray hole of the lubricator is blocked and whether the lubricating oil is sufficient.
4. Leakage: Leakage will cause insufficient air pressure, making it difficult to open and close the forced valve. The reason is that the sealing gasket is damaged or the slide valve is worn, which causes blow-by in several cavities. When dealing with the solenoid valve failure of the switching system, the appropriate time should be selected and the solenoid valve should be dealt with when the solenoid valve is de-energized. If the processing cannot be completed within a switching gap, the switching system can be suspended and handled calmly.

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