Pneumatic valves are valves that operate within pneumatic systems (systems that operate with pressurized air or gas).
What is a pneumatic valve?
A pneumatic system uses a difference in pressure between compressed gas or air to operate. Different mechanisms are used to distribute compressed gas in such schemes. Together, they form a centralized system.
This structure uses valves to control, distribute, and direct flow. By utilizing locking and regulating elements, they perform guiding and dosing functions. In pneumatics, pneumatic valves serve as a mediator between the source (compressor) and actuators (such as pneumatic actuators and pneumatic cylinders).
Special signals are used to drive such units. Pneumatic valves can be controlled by the following types of signals:
- electromagnetic
- pneumatic
- mechanical
The coils and solenoids of electromagnetic pneumatic valves are control by magnetic fields. They work on a very simple principle. Electrical current is supply to the coils from an external source. The valve stem moves as a result of interaction between the magnetic field in the coils and the solenoid.
A pneumatically operate valve is usually control by the same compress air stream that powers the pneumatic system. Their work is affect by its presence or absence in certain circumstances.
Using a lever, mechanical pneumatic valves are driven by mechanical force. Many options are available, such as 90-degree steps or quarter-turn versions. Most of the time, they perform simple tasks (opening and closing).
Devices with a combin control are also manufacture alongside the main categories. Some valves are control manually, for example, by pushing a button.
Pneumatic valve types and design
Flow lines (ports) and possible mechanism positions determine the type of valve. In the valve characteristics, these numbers are always prominently display.
The first figure shows the number of ports in the device, while the second shows available spool positions. A 4/2 pneumatic valve, for example, has four ports and two spool positions.
It is not regulated how the sign between the numbers should use (4/3, 4-3, etc.). In pneumatic systems, 3/2 and 5/2 valves are common.
Lines indicate the number of holes connecting them. Each hole and its bundle are design to perform a specific function. The main purpose of these devices is to retract and extend the medium and exhaust it.
There are some possible options for adjusting the position of the valve indicated by the figure of positions.
Depending on the initial position of the spool relative to the flow, there are two types of valves:
- Normally open
- Normally closed
A normally-closed valve means that its section is closed in its initial state (airflow is blocked). The valve opens when a signal is given, thereby opening the section of the line.
The normally-open valve initially has an open flow line (airflow moves freely) and closes when a signal is given.
Furthermore, devices may return to their original positions differently after completing their task. There are two types:
- Monostable
- Bistable
Upon termination of the signal, mono-stable valves return to their original position. A return spring is use to accomplish this. For them to work, they need one external signal.
The bi-stable valve stays in the position where the external signal ceased and does not return to its original position. To return them to their initial position, a special return signal must be sent. For such categories to operate (on/off), two external signals are require.
Pneumatic flow control valve working principle
A pneumatic distributor changes the cross-section of a pneumatic pipeline, which allows adjusting and directing the flow.
The locking and regulating elements perform this action.
Section changes can be discrete (on / off) or smoothly continuous (with adjustable parameters).
The equipment can be divided into two main structural types based on this purpose:
- Piston
- Spool
Piston valves are design to control discrete flows. By using this type of control, the channels can isolate quickly. Small systems with simple tasks are the best suit to this approach. Valve seats move along flow lines. There are usually only a few outputs in such a design.
Sliding spool valves are design to make more complex flow control operations possible. In cross-sections with a high flow rate and a complicate circuit, that equipment can use. Due to their versatility, spool valves can use in systems with 4-5 working lines as well as simpler circuits. Perpendicular to the flow axis, the spool moves.
Pneumatic valves regulate compressed air and gas flow in pneumatic systems. With their wide variety, they are capable of performing both complicated and simple tasks in flow direction control. Valve designs differ from one another.
Also, read Overview of Pneumatic Directional Valves
