3-Way Direct Acting Brass Solenoid Valve — 3/2-Way, 1/4" NPT Thread

Cematic's 3-way solenoid valve does not simply open or close a single passage. Instead, it directs fluid between two alternative outlets depending on the coil's state. Therefore, it is the correct component when the process requires selecting between two destinations, mixing two sources, or controlling a single-acting pneumatic actuator.

Its body is made of brass, and it is direct acting. Additionally, it is available in 1/4" NPT with three voltages: 24 VDC, 110 VAC, and 220 VAC. Consequently, it is the most versatile solution in Cematic's catalog for fluid switching in instrumentation, pneumatics, and industrial automation.

Operating Principle — 3-Way Solenoid Valve

A 3-way solenoid valve has three ports and two positions. Firstly, Port 1 is the pressure inlet and is always pressurized. Next, Port 2 is the first working outlet. Port 3, on the other hand, is the second outlet or the exhaust to atmosphere.

When de-energized, fluid flows from Port 1 to Port 2. Port 3, however, remains blocked. When the coil is energized, the position switches: the flow is directed to Port 3 and Port 2 is exhausted. When de-energized, finally, the spring returns the valve to its original position.

In this way, a single 3/2 solenoid controls two system states. Likewise, it reduces the number of components compared to using two independent 2/2-way solenoids.

When is a 3-way solenoid valve needed?

This is the most important selection distinction. However, it is not always obvious. The 3-way solenoid valve is the correct choice in the following cases:

• Single-acting pneumatic actuators: The 3/2 solenoid pressurizes the actuator in one position and purges it to atmosphere in the other. All with a single valve. Therefore, it is the standard scheme for spring-return cylinders.
• Selection between two sources or destinations: Switches between mains water and a cistern, or between two supply lines. Therefore, only one electrical signal is needed to make the change.
• Alternating purging and pressurization: In cleaning or hydrostatic testing systems, the 3/2 solenoid alternates between pressurizing and purging. Consequently, a single solenoid valve replaces two.
• Piloting larger diameter valves: Acts as a 1/4" signal pilot. The main valve, for its part, handles the process flow.

Construction Materials

The body is brass, making it compatible with potable water, process water, compressed air, and non-aggressive industrial gases. The plunger, on the other hand, is made of stainless steel to resist corrosion by the process fluid. The seal is NBR, which is compatible with water, air, and mineral hydraulic oils up to 80 °C.

The coil is encapsulated with IP65 protection, making it suitable for humid environments and industrial dust. Finally, the three ports have female NPT threads, which is the industrial standard in Mexico.

Technical Specifications

Voltage Selection

24 VDC voltage is standard in cabinets with PLCs and DC power supplies, making it the most common option in new installations. 110 VAC voltage, on the other hand, is for circuits available in the field and is the most widespread in Mexican industry. Finally, 220 VAC voltage is for panels with bi-phase distribution or European standard.

Fluid Compatibility

This valve is compatible with potable water and process water up to 0.8 MPa and 80 °C. It also works with compressed air up to 0.8 MPa for pneumatics and instrumentation. Likewise, it is suitable for non-corrosive industrial gases such as nitrogen, dry CO₂, and argon. Additionally, mineral hydraulic oils are compatible with the NBR seal up to 80 °C.

However, if the fluid contains suspended particles, an upstream inline filter must be installed to protect seals and orifices. On the other hand, if the temperature exceeds 80 °C, NBR degrades, so in that case, a solenoid with a Viton seal must be used. Finally, for concentrated acids or chlorinated solvents, the correct option is a solenoid with a stainless steel body.

Applications of the 3-way solenoid valve

Control of single-acting pneumatic actuators

The 3-way solenoid valve is the standard component for pneumatic cylinders with spring return. When the coil is energized, Port 1 pressurizes the cylinder via Port 2 and the cylinder extends. When de-energized, on the other hand, Port 2 connects to Port 3 and the air exhausts to atmosphere. Therefore, a single 3/2 solenoid controls the entire cycle. In this way, two independent valves are not needed.

Selection between two fluid sources or destinations

In zone irrigation or water distribution, this 3-way solenoid valve switches between two sources or destinations with a single electrical signal. Therefore, it simplifies the control scheme. In addition, it reduces the number of valves compared to using two 2/2 solenoids with mutual exclusion logic. Consequently, the control panel is more compact and economical.

Piloting large flow valves

This 3/2 solenoid acts as a signal pilot for larger diameter valves. For example, it supplies piloting air to the main valve or, alternatively, releases it to atmosphere according to the coil's state.

In addition, its direct action guarantees immediate response. Therefore, it does not depend on the main fluid pressure to operate. In short, it is the most economical way to pilot large valves from a 1/4" signal.

Dosing and industrial automation

In dosing machines, mixers, and packaging lines, the 3-way solenoid valve switches the fluid between two process paths from the PLC. The response is in milliseconds, i.e., practically immediate. Therefore, it allows automating cycles with two differentiated flow states. Likewise, it does not increase the complexity of the control panel. In conclusion, it is the most efficient solution for processes with two alternating flow states.

For the complete range of solenoid valves, see solenoid valve collection →

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