Pneumatic valve

The main function of a pneumatic valve, also known as a directional control valve, is to change the flow of air.

What is a pneumatic valve?

These valves can keep the pressure constant. There are many categories of pneumatic valves and a wide range of pneumatic valves.

Pneumatic valves are classified based on their style, type, design principle, type of operation, performance, size and application.

A pneumatic valve can do everything from turning a single flow path on and off to proportional control of pressure and flow.

Most pneumatic valves have a control function, which can be defined as the operation of the valve in any process or the control of a quantity.

A control function requires control energy which can be determined by the actuation mode which can be manual, mechanical, hydraulic or pneumatic.

Pneumatics is the use of pressurized air for mechanical movement.

Pneumatics is also used in control valves and has many applications in various industries. Other applications include dentistry, construction and mining. Air is the fuel of pneumatic power.

What is the function of pneumatic control valve?

Pneumatic control valves can reduce the pressure in a controlled manner using actuators and positioners controlled by the controller.

Controllers can detect pressure fluctuations and adjust the air supply signal to the pneumatic positioner.

A pneumatic positioner delivers air to the diaphragm and allows a valve to open.
Springs are used as an opposing force, causing the valves to close as the air pressure applied to the diaphragm is lost or reduced. Many industries rely on pneumatic control valves.

Pneumatic valve types

Pneumatic valves, also known as directional control valves, can be configured in a number of ways, including:

with the number of flow paths or switching positions that are possible

with the number of input and output ports they have

With the mechanism used to open or close the ports

According to the status of the valve when not activating it

Directional control valves that control the direction of air flow or completely prevent it are a large class of pneumatic valves with many types.

These devices can be used in a hydraulic system to connect or disconnect the system’s main source of compressed air or to advance or retract air cylinders that are part of the machine or process for which the pneumatic system is designed.

• Pneumatic valves with two-way control
• Pneumatic valves with three-way direction control
• Pneumatic valves with four-way direction control
• pneumatic spring offset valves
• Two-way valves, two positions

The two ports are connected by a passage that can be opened or closed to control the flow through the valve.

An electrically actuated solenoid valve typically switches a spool or pop valve to direct flow.

Many systems use the simple on and off function of a valve to lock, isolate and connect different parts of the system.

1/Two-way three-way valves

Three-way and two-way valves consist of three ports that are connected by passages inside the valve body.

To control a single-acting cylinder or pilot another valve, valves pressurize and depressurize an outlet port.
Three-way valves direct pressurized air to the end of the cylinder head.

Moving the spool to the opposite side prevents the current and pressure from reaching the actuator.

Since the actuator is attached to the exhaust duct, gravity or a spring must return the rod to its original position.

Three-way valves can also be used in pairs to control a two-way cylinder, effectively replacing a four-way valve.

When high cylinder speed is required, use paired three-way valves instead of four-way valves.

Connecting the three-way valves close to the cylinder ports reduces cylinder back pressure and pressure drop in the lines, allowing for higher cylinder speeds.

In high cycle applications or when intermediate positions are required, valves are also used to conserve compressed air.

2/two-way four-way valves

Two-way and four-way valves usually have four or five ports and two or three positions.

In each position, a two-position valve has two separate flow paths for actuating and reversing cylinders, rotary actuators, or bidirectional motors.

At the same time, the spool directs the flow through the pressure port and the other actuator port directs the exhaust to the atmosphere.

The four-way valve in the five-port, two-position version has five separate ports that offer different valve configurations, such as two exhaust ports or different pressures.
For example, in the latter case, the valve may exert a high pressure to actuate a cylinder and create a high clamping force, but a lower pressure (from a regulator) to release the clamp. Reducing pressure saves energy.

3/three-position four-way valves

Five-port versions of four-way and three-position valves are also available.

The most common center conditions for these valves are “all ports blocked” and “exhaust center”.

The two extreme positions that control actuator movement are the four-port and four-way valve power positions.

The center position is intended to meet some system requirements, such as locking or allowing a floating actuator.

4/pneumatic valves with spring offset

The way to change the direction of the air flow is called this type of classification of pneumatic valves.

For example, a two-way directional valve is either open (airflow is active) or closed. An actuator moves a valve spool into position to open or close each port.

The spring is used to release the valve spool and return the pneumatic valve to its original position.

Spring offset valve is a two-way directional valve that works like this.

Types of pneumatic valves based on actuator

Pneumatic valves can be classified based on the type of actuator they use.

They can be equipped with electromagnetic (electrical), air or mechanical actuators.

Solenoid valve

Solenoid valves respond to an electrical signal by opening and closing.

They regulate air flow in the pneumatic system and fluid flow in the hydraulic system. A spool valve or poppet arrangement is available.

Solenoid valves are commonly used in manufacturing environments. This is because milk needs a constant temperature to function properly.

Air valves

From a design point of view, air valves are like solenoid valves. They do not respond to an electrical signal, but to air pressure by applying force to a piston or diaphragm.

Vented valves are found in environments that require high output, but valves that do not rely on electricity and are instead operated remotely.