What is a solenoid and a solenoid valve?
Understanding the difference between a coil, mechanical actuation and fluid control.
First published: 16 March 2021 · Technical review draft: 31 October 2026
A solenoid is not the complete valve
A solenoid coil generates a magnetic field when electric current flows through it. In an electromechanical solenoid assembly, that field acts on a movable armature or plunger to produce motion. The coil or actuator alone is not a complete fluid valve.
A solenoid valve uses electrical control to regulate the passage of a liquid or gas. The coil and movable magnetic element operate the mechanism that opens or closes the flow path. The moving component is typically the armature/plunger and its connected sealing element, not the entire valve body.
Normally closed and normally open
A normally closed valve keeps its flow path closed when de-energized and opens when energized under the specified operating conditions. A normally open valve has the opposite default function. The de-energized position must therefore be checked for the particular model.
Direct-acting and pilot-operated designs
In a direct-acting valve, magnetic force moves the closing element directly. Pilot-operated or servo-assisted designs also use fluid pressure to operate the main flow path. Required differential pressure and operating limits depend on the model and must be checked in its data sheet; solenoid valves do not all share the same internal construction.
On/off and proportional control are different
An on/off valve is not interchangeable with a proportional valve. Changing the current does not mean that every solenoid will provide precise position or flow control. Proportional operation requires a valve, coil and control arrangement designed for that purpose.
Review the application, not only the part name
When requesting a component or coil, provide the existing product code, technical drawing and operating conditions. This article explains general principles; it does not replace the specific data sheet used to establish suitability, pressure limits, electrical ratings or a safety function.
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