The 5/2-Way Solenoid Valve: Principle, Applications, and Selection Guide Explained in One Article

In the field of fluid control within industrial automation, the "5/2-Way Solenoid Valve" is a core component that combines both flexibility and practicality. With its unique design of "two working positions and three fluid ports," it can precisely achieve functions like "air/fluid path switching," "medium cut-off," and "pressure release." It is widely applied in scenarios such as pneumatic actuator control and small fluid system regulation. This article will comprehensively analyze the 5/2-Way Solenoid Valve from four dimensions—definition, structure, principle, and application—and conclude with recommendations for highly compatible and reliable product choices.

I. Fundamental Knowledge: What Does "Two Position Three Way" Mean?

To understand the 5/2-Way Solenoid Valve, one must first clarify the core meanings of "Two Position" and "Three Way." These two terms directly define the valve's operating states and fluid port configuration, making them key differentiators from other solenoid valve types (such as 2/2-way or 5/3-way valves):

1. "Two Position": Two Working States

"Two Position" means the valve spool has only two stable operating states, controlled jointly by electromagnetic force and a return mechanism (such as a spring). Specifically:

• Initial Position (Normal Position): The position of the spool when the solenoid valve is de-energized. The state of connection/cutoff between the fluid ports is fixed (e.g., "P port closed, A port connected to R port").

• Working Position (Actuated Position): The position the spool moves to when the solenoid valve is energized and the electromagnetic force overcomes the spring force. The state of connection/cutoff between the fluid ports is switched (e.g., "P port connected to A port, R port closed").

In short, the core function of the 5/2-Way Solenoid Valve is "energize to switch, de-energize to reset," allowing for rapid conversion between two fluid path states using only an electrical signal.

2. "Three Way": Three Fluid Ports

"Three Way" means the valve body is equipped with three independent fluid ports. Each port corresponds to a specific function and is typically marked with internationally standardized symbols for universal application:

• P Port (Pressure Port): The "inlet" for the fluid, connecting to an external air source (like compressed air) or fluid source (like hydraulic oil).

• A Port (Actuator Port): The "outlet" for the fluid, connecting to the downstream actuator (like a pneumatic cylinder or gripper) to provide power.

• R Port (Release/Exhaust Port): The "vent/drain port" for the fluid, used to release residual medium (like compressed air from a retracting cylinder) when the actuator resets. A muffler is sometimes installed in some scenarios to reduce noise.

Note: Some brands may use "T Port (Tank Port)" instead of "R Port," but the function remains identical, serving as the medium release channel.

II. Core Analysis: Structure and Principle of the 5/2-Way Solenoid Valve

The stable operation of the 5/2-Way Solenoid Valve relies on the synergy between the "Electromagnetic Drive System" and the "Fluid Control System." Its structure and principle can be understood by examining the "Core Components" and the "Operation Sequence":

1. Core Components: Four Systems Supporting Functionality

Component Category	Key Components	Core Function
Electromagnetic Drive System	Solenoid Coil, Moving Core, Fixed Core	When energized, the coil generates an electromagnetic force, attracting the moving core to drive the spool movement; when de-energized, the force disappears, and the core resets.
Fluid Control System	Valve Body, Spool, Seals	The spool moves within the valve body, changing the connectivity between the P/A/R ports; seals (like O-rings) prevent medium leakage.
Return System	Return Spring	Pushes the spool back to the initial position when de-energized, ensuring stable path status reset.
Port System	P/A/R Ports, Connection Threads	Standardized port design facilitates quick connection with air/fluid lines and actuators (common threads like G1/8, G1/4).

 

2. Working Principle: The Closed-Loop Logic of "Energize - Switch - De-energize - Reset"

 

Taking the most common "Normally Closed (NC) 5/2-Way Solenoid Valve" (P port closed, A port connected to R port when de-energized) as an example, the complete operating cycle is as follows:

• De-energized State (Initial Position): The solenoid coil has no current, the return spring is extended, pushing the spool to block the P port. At this point, the A port and R port are connected, residual medium in the downstream actuator (e.g., cylinder) is vented through the R port, and the actuator resets (e.g., cylinder retracts).

• Energized State (Working Position): The coil receives the rated voltage (e.g., DC $24\text{V}$, AC $220\text{V}$), generating an electromagnetic attraction that pulls the moving core downward, driving the spool to compress the return spring. At this point, the P port and A port are connected, and external compressed air flows from the P port into the A port, pushing the cylinder to extend, thereby actuating the component.

• De-energized Reset (Return to Initial Position): The electrical signal is cut off, the coil's magnetic field disappears, and the electromagnetic force becomes zero. The return spring extends, pushing the spool upward to re-block the P port. Simultaneously, the A port and R port reconnect, compressed air inside the cylinder is exhausted through the R port, and the cylinder retracts, completing one control cycle.

Note: For a "Normally Open (NO) 5/2-Way Solenoid Valve," the path states in the initial and working positions are reversed (P port connected to A port, R port closed when de-energized; P port closed, A port connected to R port when energized). The core principle remains the same, with differences only in the spool's initial position and the spring's force direction.

III. Practical Application: Typical Uses of the 5/2-Way Solenoid Valve

Thanks to the advantages of "compact structure, fast switching, and simple control," the 5/2-Way Solenoid Valve has become a "standard fluid control component" in multiple sectors. Here are three typical application scenarios:

1. Pneumatic Actuator Control: The "Power Switch" of Industrial Automation

In the pneumatic systems of production lines, the 5/2-Way Solenoid Valve is central to controlling actuators like air cylinders and pneumatic grippers:

• Example: In the "part gripping" process on an automated assembly line, when the PLC issues a "grip signal," the 5/2-Way Solenoid Valve is energized, connecting the P port to the A port. Compressed air drives the pneumatic gripper to close. After gripping, the solenoid valve is de-energized, connecting the A port to the R port, releasing the air inside the gripper, and the gripper opens, achieving automated "grip-and-release" control.

• Advantage: Fast response time (typically $\le 50\text{ ms}$) meets the demand for high-frequency actions (e.g., gripper switching more than 30 times per minute).

2. Vacuum System Control: "Precise On/Off" in Low-Pressure Scenarios

 

In settings requiring a vacuum environment, such as semiconductor manufacturing or medical devices, the 5/2-Way Solenoid Valve can be used to switch the vacuum path:

• Example: Control of a vacuum cup's "hold and release." When energized, the P port (connected to the vacuum source) connects to the A port (connected to the cup), creating a vacuum to hold the workpiece. When de-energized, the A port connects to the R port (vented to the atmosphere), the vacuum is broken, and the cup releases the workpiece, preventing damage.

• Adaptability: Some 5/2-Way Solenoid Valves utilize a "direct-acting structure," which can operate without relying on medium pressure, ensuring stable work in vacuum environments ($\le -0.09\text{ MPa}$).

 

3. Small Fluid Switching: "Space Optimization" for Equipment Integration

 

In household appliances and small-scale equipment, the 5/2-Way Solenoid Valve can achieve simple switching between multiple media:

• Example: Switching between "hot water and steam" in a coffee machine. By energizing/de-energizing the solenoid valve, either the hot water path (P port connected to the tank) or the steam path (P port connected to the steam generator) is connected to the A port (connected to the outlet pipe), meeting different usage requirements.

• Advantage: Small size (some models are only $10\text{-}15\text{ mm}$ in diameter), allowing for integration inside the equipment to save installation space.

 

IV. Selection Key: 4 Core Considerations for the 5/2-Way Solenoid Valve

 

When selecting a 5/2-Way Solenoid Valve, key parameters must be matched with actual operating conditions to avoid functional failure or reduced lifespan due to improper selection:

1. Medium Type and Pressure: Choose the appropriate valve body material based on whether the medium is a "gas" (e.g., compressed air) or a "liquid" (e.g., cold water, hydraulic oil) (e.g., brass for gas, stainless steel for liquid). Confirm the working pressure range (e.g., $0.1\text{-}0.8\text{ MPa}$ for pneumatic scenarios, $\le -0.09\text{ MPa}$ for vacuum scenarios).

2. Power Parameters: Match the coil's rated voltage (e.g., industrial DC $24\text{V}$, common civilian AC $220\text{V}$) and frequency (for AC solenoid valves, confirm $50/60\text{ Hz}$) to avoid coil burnout from voltage mismatch.

3. Port Specification: Select the connection thread based on the air/fluid line diameter (e.g., G1/8 corresponds to $\Phi 4$ air line, G1/4 corresponds to $\Phi 6/8$ air line) to ensure connection sealing.

4. Environmental Adaptability: For humid environments, choose models with an IP65 or higher waterproof rating. For high-temperature environments, select coils and seals (e.g., FKM/Viton material) with a temperature resistance of $\ge 100^\circ\text{C}$.

 

V. Preferred Recommendation: Core Advantages of Airtac 5/2-Way Solenoid Valves

 

Among the many 5/2-Way Solenoid Valve brands, Airtac (Yadeke) is a preferred choice for industrial and civilian scenarios due to its characteristics of "strong scene adaptability, stable performance, and convenient installation." Its core advantages are reflected in three aspects:

 

1. Full-Scenario Coverage, Adapting to Diverse Needs

 

Airtac provides both direct-acting and pilot-operated 5/2-Way Solenoid Valves, covering different pressure and flow scenarios:

• Direct-Acting Series (e.g., 2V025-06): Operates without the need for medium pressure, suitable for vacuum ($\le -0.09\text{ MPa}$) and low-pressure ($0\text{-}0.8\text{ MPa}$) scenarios, such as vacuum cup control and small cylinder drive.

• Pilot-Operated Series (e.g., 4V210-08): Relies on medium pressure assistance for driving, suitable for medium-to-high pressure ($0.15\text{-}1.0\text{ MPa}$) and high-flow scenarios, such as large pneumatic grippers and main production line air control.

• Voltage Coverage: DC $12\text{V}/24\text{V}$, AC $110\text{V}/220\text{V}$. Port specifications range from G1/8 to G1/2, meeting the connection needs of different equipment.

 

2. High-Reliability Design, Extending Service Life

 

Airtac has specifically optimized core components to ensure long-term stable operation:

• Coil: Uses enameled wire with a temperature resistance of $155^\circ\text{C}$, coupled with a flame-retardant skeleton to prevent coil aging in high-temperature environments.

• Spool and Seals: The spool uses precision grinding, paired with NBR (Nitrile Rubber) or FKM (Fluoro-Rubber) seals, achieving a leakage rate of $\le 0.1\text{ mL/min}$, far exceeding industry standards.

• Return Spring: Uses stainless steel with a fatigue life of over 10 million cycles, preventing spring failure due to frequent operation.

 

3. Convenient Installation, Reducing Maintenance Costs

 

• Modular Design: The valve body is modular, supporting bracket or rail mounting to save space. Some models support "stackable installation," integrating multiple valves without additional piping and simplifying system layout.

• User-Friendly Features: Ports include anti-misconnection designs. The R port is pre-configured for muffler installation, allowing direct addition of silencing components to reduce operating noise.

• Quality Assurance: The entire series is ISO9001 and CE certified, ensuring quality, with fast after-sales response for quick access to replacement parts.

 

Conclusion

 

The 5/2-Way Solenoid Valve, as a "small but precise" fluid control component, is irreplaceable in automation, vacuum, and small equipment scenarios due to its "two-position switching, three-port path" design. Selecting a suitable product (such as an Airtac 5/2-Way Solenoid Valve) ensures not only system stability but also reduced long-term maintenance costs. Whether for high-frequency control on industrial production lines or integration needs in small equipment, Airtac provides a solution that balances performance and cost-effectiveness, making it a reliable choice for fluid control scenarios.