Electromagnetic valves used in industrial process control systems are divided into three categories based on their operating modes: direct acting, step-by-step direct acting, and pilot operated. From the differences in valve disc structure, materials, and principles, the step-by-step direct acting type can be divided into: step-by-step direct acting diaphragm solenoid valve, step-by-step direct acting piston solenoid valve; Pilot operated valves can be divided into pilot operated diaphragm solenoid valves and pilot operated piston solenoid valves; From the perspective of valve seat and sealing materials, it can be further divided into soft sealed solenoid valves, steel sealed solenoid valves, and semi steel sealed solenoid valves.

1、 Direct acting solenoid valve:

The solenoid valve has a simple structure, consisting of a coil, a fixed iron core, a moving iron core, and a valve body.

Principle: When a normally closed direct acting solenoid valve is energized, the solenoid coil generates electromagnetic suction to lift the valve core, causing the sealing element on the valve core to leave the valve seat and open the valve; When the power is cut off, the electromagnetic force disappears, and the sealing element on the valve core is pressed against the valve seat by the spring force, causing the valve to close. (The normally open type is the opposite of this)

Characteristics: It can work normally under vacuum, negative pressure, and zero pressure difference. The larger the valve diameter, the larger the volume and power of the electromagnetic head. If our company introduces HERION's technology to produce direct acting solenoid valves, they can be used for 1.33 × 10-4 Mpa vacuum.

Scope of application:

Due to the fact that direct acting solenoid valves mainly rely on coil electrification to generate a magnetic field, causing the moving iron core to move, the coil power is limited and only suitable for use in conditions with small diameters or low pressure.

2、 Pilot operated solenoid valve:

Principle: When powered on, the electromagnetic force drives the pilot valve to open the pilot valve. The pressure in the upper chamber of the main valve rapidly decreases, forming a pressure difference in the upper and lower chambers of the main valve. With the help of the medium pressure, the main valve closing member moves upward, and the valve opens; When the power is cut off, the spring force closes the pilot valve, and the inlet medium pressure quickly enters the upper chamber of the main valve through the throttle hole, forming a pressure difference in the upper chamber and causing the main valve to close.

Characteristics: Small size, low power, but limited range of medium pressure difference, must meet the pressure difference condition (0.01MPa).

Scope of application:

The pilot solenoid valve is suitable for use under large caliber and high pressure conditions based on the principle of "four or two turns a thousand pounds". However, it must be noted that the circulating medium must have a certain pressure. The various pilot operated solenoid valves produced by our factory require a medium pressure greater than 0.01Mpa for normal use.

3、 Distributed direct acting solenoid valve (recoil type)

Backlash type solenoid valve (i.e. no pressure difference type), also known as step-by-step direct acting solenoid valve, is an electromagnetic valve that integrates direct acting and pilot operated structures. It can open the main valve plug by the suction force of the coil under the condition of no pressure in the medium, and can also create a pressure difference in the main valve plug and open the solenoid valve under the condition of high medium pressure.

Principle: Its principle is a combination of direct action and pilot action. When powered on, the solenoid valve first opens the auxiliary valve. The lower chamber pressure of the main valve is greater than the upper chamber pressure, and the valve is opened by the simultaneous action of pressure difference and electromagnetic force; When the power is cut off, the auxiliary valve uses spring force or medium pressure to push the sealing element to close and move downwards to close the valve port.

Characteristics: It can work reliably even at zero pressure difference or at a certain pressure. Generally, the working pressure difference does not exceed 0.6 MPa, but the electromagnetic head has a large power and volume, requiring vertical installation.

Scope of application:

In general, the coil volume and power of the recoil type solenoid valve are larger than those of the pilot type, making it more suitable for use in the range of medium pressure from zero to several kilograms, and also suitable for larger solenoid valve diameters. It is particularly important to note that the recoil type solenoid valve must be installed horizontally! Small caliber recoil type solenoid valves can also be installed vertically, but users need to make special requests.