Construction & Operational Details of Solenoid Valves

Solenoid valves are control units which, when electrically energized or de-energized, either shut off or allow fluid flow. The actuator takes the form of an electromagnet. When energized, a magnetic field builds up which pulls a plunger or pivoted armature against the action of a spring. When de-energized, the plunger or pivoted armature is returned to its original position by the spring action.

Valve operation

According to the mode of actuation, a distinction is made between direct-acting valves, internally piloted valves, and externally piloted valves. A further distinguishing feature is the number of port connections or the number of flow paths ("ways").

How does a solenoid valve work?

The media controlled by the solenoid valve enters the valve through the inlet port. The media must flow through the orifice before continuing into the outlet port. The orifice is closed and opened by the plunger. The valve pictured shown is a normally-closed solenoid valve.

Normally-closed valves use a spring which presses the plunger tip against the opening of the orifice. The sealing material at the tip of the plunger keeps the media from entering the orifice, until the plunger is lifted up by an electromagnetic field created by the coil. This Engineering Information section provides a complete description of valve operation, the types of valves that are available, a glossary of terms, coils and complete flow rating data.

Principal of Operation

A solenoid valve is a combination of two basic functional units – (I) a solenoid (electro-magnet) with its plunger (or core); and (2) a valve containing an orifice in which a disc or plug is positioned to stop or allow flow. The valve is opened or closed by movement of the magnetic plunger (or core) which is drawn in to the solenoid when the coil is energized. Solenoid valves have a solenoid mounted directly on the valve body with the solenoid core attached to the valve stem. The core is enclosed and free to move in a permanently sealed tube inside the solenoid coil. This construction provides a compact, leak tight assembly.

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