How Does a Solenoid Valve Work?

A solenoid valve is an electromechanical device that controls the flow of a fluid (liquid or gas) by using an electrical current to actuate a valve mechanism. Here's a step-by-step explanation of its operation:  

1. Resting State  

- Without Electrical Current (De-energized):  

 In its default position, the valve is either closed or open, depending on its design (normally closed or normally open):  

 - Normally Closed (NC): The valve blocks fluid flow.  

 - Normally Open (NO): The valve allows fluid to flow.  

2. Electrical Current Activation  

- Electrical Current Applied (Energized):  

 When an electric current passes through the solenoid coil, it generates a magnetic field.  

3. Magnetic Field Generation  

- The magnetic field pulls the plunger or core (a movable ferromagnetic part) inside the solenoid coil.  

- This movement depends on the valve's design:  

 - In a Normally Closed Valve: The plunger moves upward, lifting a seal or opening, allowing fluid to flow through the valve.  

 - In a Normally Open Valve: The plunger moves downward, pressing a seal or closing an opening, stopping the fluid flow.  

4. Fluid Passage Control  

- The movement of the plunger directly or indirectly opens or closes the valve's orifice (passage).  

- The sealing elements (such as rubber or metal) ensure that the valve creates a tight seal to prevent leaks.  

5. Maintained Flow State  

- As long as the solenoid remains energized (current is applied), the plunger stays in its actuated position.  

- Fluid continues to flow or remains blocked, depending on the valve configuration.  

6. Electrical Current Deactivation  

- Electrical Current Removed (De-energized):  

 When the current stops, the magnetic field dissipates.  

7. Return to Resting State  

- A spring inside the valve pushes the plunger back to its default position:  

 - In a Normally Closed Valve: The plunger moves downward, blocking fluid flow.  

 - In a Normally Open Valve: The plunger moves upward, allowing fluid flow.  

Step-by-Step Summary for a Normally Closed Valve  

1. Resting State: Valve is closed, no flow.  

2. Energized: Electric current energizes the solenoid coil.  

3. Magnetic Field: Magnetic field pulls the plunger upwards.  

4. Flow Starts: The orifice opens, allowing fluid to pass.  

5. De-energized: Electric current stops; magnetic field collapses.  

6. Resting State: Spring pushes the plunger down, closing the orifice and stopping the flow.  

Applications  

- Water Control: Irrigation systems, washing machines.  

- Air Control: Pneumatic systems, compressors.  

- Oil and Gas: Refining and processing equipment.  

- Medical Devices: Fluid management in diagnostic tools.  

Solenoid valves are versatile, efficient, and widely used across industries due to their reliability and precision in controlling fluid flow.