Understanding 5/2 and 4/2-Way Pneumatic Solenoid Valves

5/2-way and 4/2-way pneumatic solenoid valves are important components in industrial automation and control systems. They are used to direct compressed air to various pneumatic devices, such as pneumatic cylinders. The main difference between these valves is in their number of ports and position states:

• The 5/2-way pneumatic solenoid valve has five ports and two position states.
• The 4/2-way pneumatic solenoid valve has four ports and two position states.

Both types of valves operate in a similar manner to manage pneumatic devices like double-acting pneumatic cylinders. The primary difference lies in how the exhaust air is managed.

• The 5/2 valve directs airflow into one port of the cylinder and exhaust from the other. With its fifth port, it allows for precise control of exhaust from both cylinder ports.
• The 4/2-way valve also controls input and exhaust air to and from the cylinder. However, it uses the same valve port for exhaust from either cylinder port, which requires identical exhaust rates in both directions.

Table of contents

• Port designations
• Circuit function
• Mono-stable vs bi-stable
• Design
• Applications
• FAQs

Port designations

Different manufacturers use different designations for the ports. However, two primary standards are widely used throughout the industry: numbers (ISO 11727) and letters.

• 5/2-way numbers (A): Supply air port (1), outlet ports (2, 4), and exhaust ports (3, 5)
• 5/2-way letters (B): Supply air port (P), outlet ports (A, B), and exhaust ports (EA, EB).
• 4/2-way numbers (C): Supply air port (1), outlet ports (2, 4), and exhaust port (3).
• 4/2-way letters (D): Supply air port (P), outlet ports (A, B), and exhaust port (R).

Circuit function

The valve's circuit function describes which ports are connected in each of the valve's states. When energized, the valve moves from one state to another, and in the case of mono-stable valves (see below), a spring returns the valve to its original position when de-energized.

• 5/2 State 1: The supply pressure port (1, P) connects to port 2 (A). Port 4 (B) exhausts through port 5 (EB).
• 5/2 State 2: The supply pressure port (1, P) connects to port 4 (B). Port 2 (A) exhausts through port 3 (EA).
• 4/2 State 1: The supply pressure port (1, P) connects to port 2 (A). Port 4 (B) exhausts through port 3 (R).
• 4/2 State 2: The supply pressure port (1, P) connects to port 4 (B). Port 2 (A) exhausts through port 3 (R).

Mono-stable vs bi-stable

Both five and four way air valves can be mono-stable or bi-stable.

• Mono-stable: A mono-stable valve's (Figure 3 labeled A & C) spool moves away from its resting position when the valve's single coil is energized. The resting position is the normal position the valve maintains when not energized. When de-energized, a spring moves the spool back to its resting position. Mono-stable valves require constant power to maintain the energized position.
• Bi-stable: Bi-stable valves (Figure 3 labeled B & D) have two solenoid coils. The spool moves between states depending on which coil is energized. When de-energized, the spool remains in its current state. The opposite coil must be energized to move the spool to the other position.

Design

5/2 and 4/2-way pneumatic solenoid valves are available in numerous design variations regarding size, material, color, connection interfaces, and more. This variety is necessary to meet various requirements, such as those in medical use, food processing, and dusty and explosive environments.

Most of these valves have a movable spool with seals along its length, all within a central cylinder. The valve ports connect to this central cylinder, and the seals block or connect to the valve ports when the spool moves through the cylinder.

Direct and pilot operated

Pneumatic solenoid valves can be direct or pilot (indirect) operated:

• Direct: The magnetic actuator directly moves the spool.
• Pilot: The valve uses inlet pressure to help move the spool. A small internal pneumatic cylinder actuates the spool. The valve's magnetic actuator controls the filling and emptying of the cylinder.

Manual override

A 5/2 solenoid valve or 4/2 way pneumatic solenoid valve can have a manual override or lock mechanism. A lock mechanism is beneficial during maintenance; the valve does not change position until the lock is released. The actuated elements (e.g., cylinder or grippers) also retain their position. The system can be tested without actuating the valve with a manual override. Furthermore, the valve can be manually switched by pushing the override button.

Connector types

Various connector types and designs are available, serving different purposes depending on the solenoid valve's requirements. For example, connectors can protect solenoid valves against power surges and have LED lights that indicate the valve's power status. Learn more about connectors in our DIN connector overview article.

Applications

4/2 and 5/2-way pneumatic solenoid valves can both operate double acting pneumatic cylinders and pneumatic actuators that require control in both directions. A 5 2 valve, however, with its extra exhaust port, can independently control the exhaust rate in both directions, whereas a 4/2-way valve requires both directions to share the same exhaust rate.

Controlled exhaust in both directions

• High-speed applications: In high-speed applications, such as packaging, sorting systems, or assembly lines, the speed of actuation is crucial. A 5 2 way solenoid valve with separate exhaust paths can allow for quicker air pressure exhaust, resulting in faster actuation times.
• Precision applications: In applications requiring precise control of movement, like in robotics or precision machining, separate exhaust paths can provide better control of the actuation speed in both directions.
• Safety-critical applications: In safety-critical applications where the failure of one part could have serious consequences, separate exhaust paths can provide redundancy. If one exhaust path fails, the other can still function.

Same exhaust in both directions

• Single-acting cylinder applications: In applications using single-acting cylinders where spring return is used, a common exhaust path (four way air valve) is sufficient since the return action is not dependent on the exhaust air.
• Less critical speed applications: In applications where speed of actuation is not critical, a common exhaust path can be used. This might include general purpose pneumatic systems, door openers, or simple mechanical movements.
• Cost-sensitive applications: 4 way 2 position solenoid valves can be less expensive than 5 way solenoid valves. If the application doesn't require high speed or precision, a 4/2 way pneumatic valve might be more cost-effective.

FAQs

What is a 5/2 way solenoid valve?

A 5 2 solenoid valve has five ports and two states. It can switch between two different states to control airflow to and exhaust from both air ports of a pneumatic cylinder or actuator.

What is a 4 way solenoid valve?

A four way two position valve has four ports and two positions. Two ports supply air to either side of a double acting solenoid valve and the remaining port handles exhaust from the cylinder.