What is a solenoid valve and in what applications is it used?

Solenoid valves operate on the principle of electromagnets: the coil being energized causes the valve to open, while loss of power causes it to return to its original position (although some require manual reset). The main function of a solenoid valve is to cut off the air supply to a valve, enabling pneumatic instruments such as control valves/switch valves to quickly reach a certain state (open/close). Other solenoid valves can also be used to shut off clean process media, such as water, air, and oil. PS: All are small pipes with a DN50 or less.

There is a solenoid valve installed on the pipe of my household solar water heater. The water supply and drainage share the same plastic pipe. The solenoid valve opens when power is supplied and water is introduced. When the power is cut off, the solenoid valve closes; a check valve is located behind it, and these components are integrated together so that water flow downward does not affect the water supply pipes. Human wisdom is everywhere.

Solenoid valves are primarily used to switch gas circuits; they are generally installed on the output gas line of valve positioners for interlock protection. When a fault occurs, the solenoid valve loses power, which in turn changes the gas flow path and ensures that the control valve returns to the position required for process safety, thereby safeguarding the safety of the system

Adding to what was said above: in addition to its role in chain protection, it functions as a valve controller in sequential control by switching the air circuits

　Solenoids are basic automated components used to control fluids, and they belong to the category of actuators； It is not limited to hydraulics or pneumatics. 　　Solenoids are used to control the direction of hydraulic flow. The mechanical devices in factories are generally controlled by hydraulic systems, which is why solenoids are employed. Working principle: The solenoid valve contains a sealed chamber with holes located at various positions; each hole leads to a different oil pipe. At the center of the chamber is the valve, with two electromagnets on either side. When the coil of the magnet on one side is energized, the valve body is attracted to that side. By controlling the movement of the valve body, it is possible to block or allow fluid to pass through different oil outlet holes. The oil inlet hole remains open, allowing hydraulic oil to flow into the various oil outlet pipes. The pressure of the oil then pushes the piston inside the cylinder, which in turn drives the piston rod, and the piston rod activates the mechanical mechanism. In this way, controlling the current to the electromagnet controls the mechanical motion.

Solenoid valves are used in chemical plants, in the actuation devices that are part of interlock systems; they allow for rapid shutdown of the gas supply, thereby ensuring the safety of related equipment!

DN500 is also acceptable; there’s no need to be absolute. You can refer to BURKERT’s instructions, which are an excellent resource for solenoid valves, covering both the principles and model selection

You are referring to the electromagnetic directional control valve, a type of solenoid valve

Solenoids come in two types: single-electric-control and dual-electric-control. The single-electronic-control type is mostly used as an actuator and operates in a monostable mode; its working principles include direct-action and differential-pressure action types. The dual-control type is mainly used for electrical/gas signal conversion, and its valve operation mode is a bistable operation mode. The direct-acting principle works as follows: when the solenoid coil is powered, a magnetic field is generated; this field attracts the movable iron core within the coil, and the core drives the valve stem to open the valve directly, allowing the fluid medium to flow from the inlet to the outlet. When the solenoid valve loses power, the magnetic attraction disappears, and the valve core returns to its original position under the force of gravity, closing the valve. Direct-acting solenoid valves are suitable for low-pressure and small-diameter applications. It operates on a differential pressure principle; the valve opens by utilizing the pressure difference created on both the upper and lower sides of the main spool to open or close the main valve port.