Solenoid valves are designed to control the rate of fluid flow and air powered tools, systems, and motors. A solenoid valve is used as a control valve and is the most frequently used control element in fluidics. As a control valve, a solenoid will perform tasks such as shutting off, releasing, dosing, distributing, or mixing fluids. These valves offer fast and safe switching with high reliability, long service life, and a compact design.
A solenoid valve is an electromechanical actuated control valve. It's controlled by an electric current through the valve. Also called an electronic valve or electric valve, it will shut off when electrically energized and allow flow when de-energized. An electrically energized coil or electromagnet inside the solenoid valve serves as the actuator. When energized by an electrical current, a magnetic field builds up and exerts force on a plunger which is pulled toward the center of a coil or spring, causing the valve to open.
Types of Solenoid Valves
There are several types of solenoid valves. Based on the mode of acuation, a distinction is made between direct valves, internally piloted valves and externally piloted valves. Another distinction is the number of port connections or flow paths known as ways.
Direct acting solenoid valves
Direct acting valves use only the power from the electromagnet to open and close the valve. The seat seal is directly attached to the valve core. When energized, a coil magnetically opens the solenoid valve using direct action, lifting the shaft and seat without using an outside pressure. When de-energized, it closes. These types are best for controlling smaller flow rates.
Pilot operated solenoid valves
Also known as servo-assisted valves, pilot operated valves use electromagnetic power combined with the operating pressure from flowing air/liquid/gas in the system as a pilot to actuate the valve spool to open and close it. These valves include both internally piloted valves and externally piloted valves. They provide higher flow rates and can operate at high pressures and temperature ranges with lower power consumption.
In a two-way solenoid valve, each of its two ports can be alternatively used to permit flow as well as close it off.
As the name implies, a three-way solenoid valve has three ports. They are used in applications when alternative and exhaustive pressure are required for operation. Three-way valves are used in coffee machines and dishwashers.
With four or more port connections, a four-way solenoid valve is commonly used with a dual-acting cylinder or actuator. Half of the ports supply pressure and the other half provide exhaust pressure.
Solenoid valves come in a variety of materials including brass, stainless steel, aluminum, and plastic. When choosing a valve, you should consider what type of fluid will be used in operation and what type of material should be selected for the seals to ensure that the valve functions properly.