Differences Between 2-Way and 3-Way Pneumatic Solenoid Valves
Pneumatic valves are commonly referred to by their number of ports and actuation method. With this article, we are comparing 2-way Solenoid Valves and 3-way Solenoid Valves. Although they are operationally similar, they do perform different functions in pneumatic systems.
What is a 2-Way Pneumatic Solenoid Valve?
A 2-way solenoid valve has an inlet and an outlet port to start and stop pressurized media flow in one direction only. It has two positions (energized and de-energized) and forms the most precise control of media.
These valves are powered by an electromagnetic coil that activates a plunger to open or close flow through the valve body. There are a variety of designs that offer functions over wide pressure and temperature ranges, and for a variety of flow capacities and gas media choices.
When high flow capacity is required, pilot operated valves are available. With these valves, a small integrated 3-way solenoid valve is employed to pilot operate a large 2-way valve. In these cases, a minimum pressure is required, typically starting at 30 psi (2 bar).
Advantages of a 2-Way Solenoid Valve
Two-way solenoid valves are quite simple, making them reliable and easy to install and maintain. They’re best for applications that require precision timing and control and are available in different sizes, configurations and materials.
Advantages of using a 2-way include:
- Precise flow output
- Positive shut-off
- Low cost
- Durability
- Potential to control a variety of gas media
Common Applications for a 2-Way Solenoid Valve
- Dump Valve
- Fill Valve
- Pulse Valve
- Isolation Valve
- Check Valve
- Shut Down Valve
What is a 3-Way Pneumatic Solenoid Valve?
A 3-way solenoid valve functions similarly to a 2-way, but has an additional port, providing a directional control function, i.e. allowing media to flow in two directions.
The outlet port is the “common” port. It is open to the “third” port in one position (while blocking the path to the inlet port) and opens to the inlet port in its second position (and blocked third port).
In compressed air applications, the most common use of 3-way solenoid valves have the third port perform an exhaust function, venting downstream compressed air to atmosphere when open to the common port.
Some 3-way solenoid valves can function with two pressurized inlet ports and a single common outlet port to perform a “selecting” function. A “diverting” function is possible when the pressurized supply port is piped to the common port, directing flow to inlet, or third port.
Advantages of a 3-Way Solenoid Valve
A common and versatile component in pneumatic automation, 3-way pneumatic solenoid valves actually serve the purpose of two 2-way valves in most applications. Many 3-way types are offered as “multi-purpose” and can be piped normally closed, normally open, diverting or selecting functions.
Further, with its third port plugged, these valves function as 2-way solenoid valves. Two 3-way solenoid valves can provide a 4-way function and yield better control in those applications.
With a 3-way valve:
- Pilot operate remotely located work and process valves
- Control single-acting, spring return air cylinders and air actuators
- Divert flow direction
- Select between two pressures or different media
- Plug third port to function as 2-way
Humphrey Products Has Your 2- and 3-way Solenoid Valve Needs Covered
Let our team help you find the right 2-way or 3-way solenoid valves from a wide variety of designs and sizes to suit your application requirements and optimize performance. With 50 years of experience providing solutions to the most demanding applications, we are a valuable resource for design engineers. Review our products and contact us for more information.