Normally closed: when the coil is energized, the pilot valve core is closed, the pilot hole is opened, the upper chamber pressure is relieved, the piston is pushed by the lower chamber medium pressure, and the solenoid valve is opened; when the coil is powered off, the pilot valve core is reset by the spring, pilot The hole is closed, the upper cavity of the valve is pressurized by the piston orifice and the thrust of the return spring is closed, and the solenoid valve is closed.
Normally open: when the coil is energized, the pilot hole is closed, the upper cavity of the valve is pressurized by the piston throttle hole and the thrust of the return spring is closed, and the solenoid valve is closed. When the coil is de-energized, the pilot valve core is reset by the spring, the pilot hole is opened, the upper chamber of the valve is depressurized, the piston is pushed by the medium pressure of the lower chamber, and the electromagnetic valve is opened.
Normally closed solenoid valve operation principle: the coil is energized, the gas circuit is connected, once the coil is powered off, the gas circuit will be disconnected, which is equivalent to "jogging."
Normally open solenoid valve operation principle: power to the coil, the gas circuit is disconnected, once the coil is powered off, the gas circuit will be connected, which is also "inching."
It is usually selected based on the duration of the continuous operation: normally closed, normally open, or sustainable power.
1, when the solenoid valve requires a long time to open, and the duration of the excess time off should be selected normally open type.
2. If the opening time is short or the opening and closing time is short, select the normally closed type.
Electromagnetic valve features:
1, low density and high filling;
3, corrosion resistance;
4, water vapor resistance;
5, resistance to hot water performance;
6, electrical performance;
Solenoid valve classification:
Electromagnetic valves at home and abroad are divided into three major categories (ie, direct-acting, step-by-step, and pilot-type), and the difference between the valve structure and material and the principle is divided into six. Sub-categories (straight-acting diaphragm structure, step-by-step diaphragm structure, pilot diaphragm structure, direct-acting piston structure, step-by-step direct-acting piston structure, pilot piston structure), divided into 2 positions and 2 passages according to the number of gas paths, 2 Bit 3 pass, 2 pass 4 pass, 2 pass 5 pass.
Solenoid valves are divided into single and double electric control, referring to the number of electromagnetic coils, single coil is called single electric control, double coil is called double electric control, 2 2 pass, 2 pass 3 pass general It is a single electronic control (single coil), 2-digit 4-pass, 2-digit 5-pass can be single electronic control (single coil), or double electronic control (double coil).
First, according to the controlled pipeline in the media and the use of different operating conditions can be divided into solenoid valves: electromagnetic valve for the use of gas, electromagnetic valve for gas, steam solenoid valve, gas solenoid valve, solenoid valve for oil, fire-specific solenoid valve , Refrigeration solenoid valve, anti-corrosion solenoid valve, high temperature solenoid valve, high pressure solenoid valve, solenoid valve without pressure difference, ultra-low temperature solenoid valve (cryogenic solenoid valve), vacuum solenoid valve and so on.
Second, according to the different internal structure of the solenoid valve can be divided into pilot, direct-acting, compound, recoil, self-retaining, pulsed, bistable, bidirectional and so on.
Third, according to the use of electromagnetic valve material can be divided into: cast iron body, copper body (cast copper, wrought copper), cast steel body, all stainless steel body (304,316, etc.), non-metallic materials (ABS, PTFE).
Fourth, according to the pressure of the media in the pipeline can be divided into: vacuum type (-0.1 ~ 0Mpa), low pressure type (0 ~ 0.8Mpa), medium pressure type (1.0 ~ 2.5Mpa), high pressure type (4.0 ~ 6.4Mpa), Ultra high pressure type (10~50Mpa)
V. According to different operating voltages, it can be divided into: AC voltage: AC220V 380V 110V 24V; DC voltage: DC24V 12V 6V 220V; common voltage is AC220V DC24V, users are recommended to use common voltage and special voltage as long as possible.
Sixth, according to the electromagnetic valve protection level can be divided into: explosion-proof, waterproof, outdoor type protective performance: waterproof, explosion-proof (Exd IICT4, (Exd IICT5), anti-corrosion.
Direct acting solenoid valve:
Principle: When the power is turned on, the electromagnetic coil generates an electromagnetic force to lift the closing member from the valve seat and the valve opens. When the power is turned off, the electromagnetic force disappears. The spring presses the closing member against the valve seat and the valve closes.
Features: It can work normally under vacuum, negative pressure and zero pressure.
Distributed direct-acting solenoid valve:
Principle: It is a combination of direct acting 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 part and the valve opens. When the inlet and outlet reach the starting differential pressure, after the power is turned on, the electromagnetic force leads the small valve, the pressure in the lower chamber of the main valve rises, and the pressure in the upper chamber decreases, thereby pushing the main valve upwards by utilizing the pressure difference; when the power is off, the pilot valve utilizes the spring. Force or medium pressure pushes the closure and moves it downwards to close the valve.
Pilot solenoid valve:
Principle: When the power is turned on, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, and a pressure difference between the lower part and the upper part is formed around the closing part. The fluid pressure pushes the closing part to move upwards and the valve opens; when the power is turned off, the spring force leads the pilot. The hole is closed and the inlet pressure quickly bypasses the chamber to form a lower, upper high pressure differential around the valve closing member. The fluid pressure pushes the closing member downward and closes the valve.
Two-position solenoid valve refers to the solenoid valve spool has two different working positions (open, close). Solenoid valve two-way, three-way solenoid valve body has two or three channel ports; for example, two-position two-way solenoid valve is one in and one out (two channels, the most common common) two three-way solenoid valve The control fluid is one in and two out (two out are one normally open and one normally closed); the pneumatic commutation solenoid valve is one in, one out and one exhaust, and the hydraulic pressure is in one out and one in return.
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