Circuit function
A 5/2-way pneumatic valve has five connection ports and two states. A pressure port (P,1), two control ports (A,2) and (B,4), and two exhaust ports (EA,3) and (EB,5) connect to the device that needs to control. There are two states of the valve:
- The Pressure port (P,1) connects to port (A,2), while port (B,4) vents through the exhaust port (EB,5)
- The pressure port (P,1) connects to port (B,4), while port (A,2) vents through port (EA,3).
Port designations
There are different port designations used by different manufacturers. ISO-1210-1 is also a standard designation. We strive to maintain this standard in our articles as much as possible. ISO uses numbers to identify the different ports. Some manufacturers, however, use letters to clarify port designations.
As in the example, ISO port 1 is also designated with a letter P from pressure, which is the point where the pressure line connects. Outlet ports (or working ports) with ISO designations 2 and 4 are alternatively designated A and B. ISO designation numbers 3 and 5 correspond to the corresponding exhaust ports. Alternative letter designations for these ports are EA and EB, which mean exhaust from A and exhaust from B, respectively. The exhaust port number 3 (ISO) on valves with a single exhaust port, such as 3/2-way or 4-way valves, is alternatively designated with the letter R (relief).
Four connection ports and two states define the 4/2 pneumatic valve. There is a difference in the number of exhaust ports between the two valve types:
- There are two independent exhaust ports on a 5/2-way pneumatic valve
- 4/2-way valves have only one common exhaust port
As a result, both ports (A,2) and (B,4) are connected to the exhaust port (R,3). 5/2-way valves offer additional control options due to their additional exhaust ports. By controlling the flow rate through each exhaust port individually with throttle valves, a double-acting pneumatic actuator can adjust its speed in both directions.
A mono-stable valve or a bi-stable valve can use. 5/2-way mono-stable valves return to their resting position when not actuated. A spring returns the valve to its resting position. In other words, mono-stable valves require constant actuation (pneumatic, electrical, or manual) to remain actuated. A 5/2-way bi-stable valve keeps its position during power loss, requiring a separate action to switch the valve from one position to the other.
The following circuit functions are possible:
- 5/2-way mono-stable
- 5/2-way bi-stable
- 4/2-way mono-stable
- 4/2-way bi-stable
Different methods can use to operate 5/2- and 4/2-way pneumatic valves:
- Electrically (solenoid valve)
- Pneumatically
- Mechanically
- Manually
A symbol can represent the circuit function and valve actuation. Following are the circuit function symbols for both 4/2-way and 5/2-way solenoid valves.
Design
The basic function of pneumatic 5/2-way valves remains the same, but there is an unlimited variety of sizes, materials, colors, and connection interfaces available. A wide range of requirements, such as medical use, food processing, dusty environments, explosive environments, etc., require this.
Most 5/2-way valves have a movable spool with seals along their length. Connected to this central cylinder are the valve ports. As the spool moves through the cylinder, the valve ports are connected or blocked. Additionally, the valve can operate directly or via a pilot. The actuator is directly connected to the spool indirect operation. As part of the pilot operation, the valve uses the inlet pressure to move the spool. An internal pneumatic cylinder actuates the spool in the valve. An actuator, such as a solenoid, controls the filling and emptying of this cylinder. A 5/2-way valve is usually operate by a pilot. Valve parts include:
- Housing
- Seals
- Piston
- Spool
There are many types of 5/2-way valves available with manual override or even with lock mechanisms. When the lock mechanism is engaged, the valve maintains its position until the lock is released, so actuated pneumatic elements, such as grippers or cylinders, remain in place. It is possible to use the manual override to test the system since the valve does not need to electrically energize. It is enough to push the override button to switch the valve. The disadvantage of a lock mechanism is that operators might forget to remove it.
It is important to consider the type of electrical connector when selecting a solenoid valve. There are a variety of connector designs available from some manufacturers, as well as DIN43650 type A, B, and C connectors. Different IP grades indicate how well the connectors resist water and dust ingress. As an alternative connector option, an indicator light can use to detect valve malfunctions or power outages.
Some valves can mount on a manifold. It is an easy way to group multiple pneumatic valves and save space, connectors, and tubing. It is possible to equip manifolds with pressure regulators, check valves, etc.
5/2-way valves can made into 3/2-way valves by blocking one inlet and one outlet (A-EA or B-EB). It is possible to build a 5/2-way bi-stable valve with two 3/2-way mono-stable valves.
Typical applications
5/2-way valves are use to control double-acting pneumatic actuators, including pneumatic cylinders, rodless cylinders, grippers, and rotary actuators. To move in both directions, double-acting actuators need compressed air. Knowing more about the system’s design and requirements is necessary to determine whether a mono-stable or bi-stable 5/2-way valve should use.
For determining which valve can use, the following information must provide:
- In the system, how many actuators are there?
- On the PLC, how many I/O ports are there?
- Actuator’s positions
- Normal working conditions
- Safety requirements
Each actuator or group of actuators requires its control valve, so the number of valves is determin by the number of actuators. There is a limit to the number of coils that can energize by the PLC. A mono-stable valve (with one solenoid coil) requires less wiring and PLC outputs than a bi-stable valve (with two solenoid coils). There are some manifolds with internal wiring and one connector that connects all the valves, such as a 25-pin D-SUB connector. Compared to 25 mono-stable valves, only 12 bi-stable valves could install in this case.
The choice between mono-stable and bi-stable valves is often driven by safety concerns. During power loss, it might be desirable for the actuator to return to the base position in some machine designs to prevent machine damage or injury. Mono-stable valves are recommend in such situations. Other designs require bi-stable valves if the actuator must remain in the last position.
Airmax Pneumatics Ltd is a Leading 5/2 way Single Solenoid Valve Manufacturer and supplier in India.
Also, read A Guide To Making The Right Choice Of Industrial Ball Valves