Solenoid Valve Structure and Operating Principle

A solenoid valve is a product with a relatively high switching frequency. Its structural principle is that of a gate valve, operating up and down, controlled by a shut-off seal.

Solenoid valves are used in applications with smaller diameters, generally DN50 and below. Larger diameters are not recommended. Solenoid valves have a wide range of applications, including gas and liquid handling. As long as the medium is relatively clean, a solenoid valve can be chosen. The piping of a solenoid valve has a directional flow, typically only allowing flow in one direction.

Solenoid valves are generally classified into three types: direct-acting, step-by-step direct-acting, and pilot-operated.

1. Direct-acting solenoid valves are used in environments and media with very low pressure requirements. Typically, the pressure of the medium used by the solenoid valve is below 1 kg.

2. Step-by-step direct-acting solenoid valves are suitable for pressures above 1 kg (generally around 40 kg).

3. Pilot-operated solenoid valves are suitable for higher pressures, such as tens or hundreds of kg.

First, the choice of medium and then the choice of operating pressure are important. These two aspects are crucial for the selection of solenoid valves. The medium requirements for solenoid valves are mainly divided into two types: piston type and diaphragm type.

(1) Piston-type solenoid valves use piston sealing, resulting in better sealing performance. In terms of lifespan, piston-type solenoid valves have a much longer lifespan than diaphragm-type solenoid valves. Our tests show a normal lifespan of around 3 million cycles, while diaphragm-type solenoid valves have a lifespan of 1 million cycles. Structurally, most solenoid valves are of the step-by-step direct-acting type. Both step-by-step direct-acting and pilot-operated types require a pressure differential to open the solenoid valve.

The pressure differential is needed to drive the entire valve. What is pressure differential? Pressure differential is the pressure before the valve minus the pressure after the valve.

The basic working principle of a piston-type solenoid valve: There is a sealing ring under the piston. The sealing ring under the piston closes the valve body. There is a valve port under the valve body. The piston moves up and down to close or open the valve. The valve is opened by energizing the coil to generate a magnetic field. The magnetic field drives the movable iron core. The movable iron core moves upward and then drives the piston. The valve is opened by the pressure difference.

(2) Diaphragm-type pilot valve working principle: It is usually divided into two parts: a main valve and a secondary valve. The magnetic field generated by energizing the coil drives the movable iron core. The movable iron core is made of magnetic stainless steel. The movement of the iron core opens the secondary valve. The medium flows to the secondary valve. At this time, the pressure difference lifts the diaphragm of the main valve and the spring of the main valve, and the valve opens. When selecting a solenoid valve, it is usually chosen when the diameter is less than 50, the frequency is relatively high, and the medium is relatively clean. Choosing a solenoid valve will result in a relatively low cost.