Pneumatic Control Valve-FAQ 

 

The pneumatic control valve regulates the fluid flow and acts as the correcting unit of the automatic control system. As pneumatics is the major part of many industries, there are safety concerns in the pressurized systems. Pneumatic control valve acts as an automation control by using pressurized air or gas.

If you want to purchase a pneumatic control valve for your application, it is better to have detailed knowledge about the product. This guide will answer common pneumatic control valve questions to provide general information about the product. Hopefully, you will know enough information about the pneumatic control valve at the end of this guide.

1. What is pneumatic control valve?

A pneumatic control valve is an essential tool for controlling the pressure and air through the pneumatic system.

Pneumatic system is part of many industrial applications. The pneumatic system depends on compressed air to transmit power, and a pneumatic control valve is part of that system. A pneumatic control valve controls airflow by regulating the passage into tubes and pipes in an automated pneumatic system.

The actuator causes the pneumatic valve to open or close; it could be manual, electrical, motorized, or pneumatic. The pneumatic control valve is at the heart of every pneumatic system. The application determines what pneumatic control valve is suitable for the operation of the system.

2. How does it work?

There is pressurized air into the diaphragm, which pushes it against the walls into the compressor. Once there is enough pressure, it pushes the spring and diaphragms down that causes the valve stem to press downward and close. The valve stem moves back to its position, causing it to open once the air exhausts away from the diaphragm. When the pressurized air holds, the valves control the speed of air from entering into the cylinder.

The pneumatic control valve controls the pressure by opening and closing the area through which air moves. The pneumatic control valve has a profound effect on industrial machines, and a faulty pneumatic valve can impact the accuracy and effectiveness of the machine.

3. What are the types of pneumatic control valve?

The pneumatic control valve controls the pressure, rate, and amount of air within the pneumatic system. The pneumatic control valve can be classified using various approaches. The approaches include:

• The number of entry and exit ports.
• The mechanism responsible for opening and closing of ports
• Number of available flow paths
• The position of the valve when it is un-actuated state

There are three primary types of pneumatic control valves.

Two-way directional control pneumatic valves

The two-way pneumatic control valve passes air in two directions through two ports. If the port is closes, no air can flow through the valve. If the valve port is open, air passes through a first or second port opposite.

Three-way directional control pneumatic valves

This three-way directional pneumatic control valve has three ports that serve a different purpose. The first port connects the valve to the actuator. The second port connects the valve to airflow, and the last one serves the purpose of the exhaust exit. When the first two ports are open, the third one is closed. When the first and third one is open, the second one is closed. The actuators connect the three-way valves in cylinders.

Four-way directional control pneumatic valves

This directional control valve has four ports. Two of these ports are connected with the actuator, one to pressurized airflow, and the other acts as an exhaust pathway. In some cases, an additional port is added, which makes it a five-way pneumatic control valve. Four-way is the most common pneumatic control valve in pneumatic systems.

Spring offset pneumatic control valve

This type of pneumatic control valve is used where the direction of airflow is switched. In a two-way directional valve, one is open and the other is closed, and the actuator moves a valve into position. For bringing the pneumatic valve into the original position, a spring releases the spool. If the two-way directional valve also uses spring for releasing spool, it’s also called a spring offset valve.

4. What are the functions of pneumatic control valve?

The function of the pneumatic control valve is to control the fluid and regulate  pressure , flow , temperature in the pipe system . It is done by decreasing the pressure by using actuators and controllers to pilot them. The function of the controller is to sense the pressure fluctuations in the system and then direct the air supply signal to the pneumatic positioner.

The pneumatic positioner supplies the air to the diaphragm, which opens the valve. If there is any loss or reduction of air pressure, the springs act as opposing forces and close the valve. The pneumatic control valve has usage in many industries.

5. What are two major forms of pneumatic control valve actuators?

Pneumatic control valve actuators have two forms, piston actuators and diaphragm actuators. Where the diaphragm actuator is too short, or thrust is too small, piston actuators are used. These actuators can withstand higher input pressures and smaller cylinder volumes. In diaphragm actuators, the diaphragm has compressed air and is constant. In these pneumatic control valve actuators, the air supplies to one side of the diaphragm; this can be direct acting or reverse acting.

The compressed air pressure drives the operating force to the flexible diaphragm. The force coming from the air pressure overcomes the force exerted by the spring. The diaphragm pushes upward and pulls the spindle up. If it connects with the direct-acting valve, it opens the plug. The spindle then moves the valve from a closed to an open position.

6. What signals control the pneumatic control valve?

Pneumatic control valve controls and regulates the flow in the pneumatic system. It directs and regulates the flow by locking and regulating elements. The signals are sent by the units and control the pneumatic valves include electromagnetic, pneumatic, and mechanical.

The magnetic fields on coils control the electromagnetic pneumatic valves by sending current from the external electric source to the coils, making the valve stem move. The compressed air controls the pneumatic operated valve system by the compressed air which operates in the pneumatic system. The mechanical force drives the mechanical pneumatic valves by using a lever. They perform simple tasks of opening and closing.

7. What are the designs of pneumatic control valve?

The flow type within the pneumatic control valve is determined based on flow lines and possible mechanism positions. Various characteristics indicate the number of ports in the device and spool positions. For example, the pneumatic control valve with a 4/2 position has four ports and two spool positions. The popular models of the pneumatic control valve in pneumatic systems are 3/2 and 5/2. The spool position determines the types of valves, which are generally open, and normally closed.

In the normally closed control valve, initially, the section is closed, and airflow is blocked. When the signal is given, it opens the valve and section of the line. A normally open valve has an initial state with an open flow line and closes after getting the signal. Also, the devices return to their original position differently after completing the work. A monostable valve goes back to the original position after the termination of the signal. Bi-stable valves do not return to their original position once the signal is terminated. For getting back to the original position, a special signal is sent.

8. What is the working principle of pneumatic control valve?

The pneumatic distributor in a pneumatic control valve performs the function of changing the cross-section in the pipeline by adjusting the flow by locking and regulating elements. It is performed by two section changes, discrete (on/off) or smoothly continuous (with adjustable parameters). These section changes divide the equipment into two types.

Piston valves are designed for discrete flow control, it provides quick isolation between channels and is suitable for small tasks. Sliding spoon valves are suitable for complex flow operations. You can use them for a high-flow rate in a complicated circuit. The sliding spoon valves are suitable for simpler structures because of their versatility. The pneumatic control valve is the regulator for measuring gas and airflow in pneumatic systems.

9. What is meant by pneumatic control valve designations?

There are various valve configurations of pneumatic control valve that define the parameters, including ports, switching position, and non-actuated state. To define these configurations, a numbering system is used where a slash separates two numbers. The first number shows the number of ports in the valve, and the second one reflects the number of switching positions. For example, 3/2 pneumatic control valve means there are three ports and two switching positions, and 5/2 means there are two switching positions and five ports.

These options also define the non-actuated state of the pneumatic control valve. A 2/2 valve is available for the closed position, which means that the valve does not allow airflow between the ports, and it is un-actuated. In a normally open valve, the valve provides airflow, and it is actuated. Similarly, in the three-way valve, one port is always open. The closed port results in blocking the airflow. Pneumatic control valve commonly includes 5/3, 5/2, 4/2, 3/2, and 2/2.

10. What are pneumatic control valve specifications?

• The specifications of the pneumatic control valve help users to characterize their valves differently. The specifications are dependent on several factors, such as actuation mechanism, manifold design, and porting. Following are the pneumatic control valve specifications.
• The operating pressure or pressure range – the maximum limit of pressure that a valve can handle
• Operating medium – the compressed air that the valve can control
• Flow capacity – the capacity of the valve to measure the airflow with the flow coefficient represents the constant between flow rate and differential pressure.
• Cycle rate – the number of valve cycles that a valve can handle per unit of time
• Response time – How valve respond after actuated in a given time period
• Port size – the dimensions of the pneumatic control valve that define the port sizes on the valve

11. What are the pressure regulators in pneumatic control valve?

A pneumatic control valve allows the flow of pressurized air by circulating air in the pneumatic system. The pneumatic control valve has various passages for air and flow patterns, so they are classified according to the number of ports it possesses and is suitable for various applications. The important component in the pneumatic control valve is the pressure regulator that controls pressure through an actuator in the pneumatic system.

The appropriate pressure range is for minimum and maximum pressure requirements. The pressure valve ensures that the pressure must remain constant regardless of the changes in pressure throughout the operation. Pressure regulators in the pneumatic control valve have a sensor that monitors the pressure in the pneumatic system.

12. What is the importance of a pneumatic control valve in a pneumatic system?

The pneumatic system is a vital part of various industries. It uses rotational motion to create a force of energy. There are various components of the pneumatic system, and each is inevitable for the proper working of the other. The pneumatic control valve is among the most important component in the pneumatic system. It holds and regulates compressed air to avoid any leakage in the system.

The compressed air acts as a catalyst to control fluid or oil components into the actuator. The pneumatic control valve is also known as a directional control valve and can maintain the pressure in the pneumatic system. They can be categorized based on type, model, design, operating principle, and application.

13. How is the pneumatic control valve activated?

There are various ways to activate the pneumatic control valve. It could be manual, air-piloted, or solenoid operated. The 2-way and 3-way control valves are usually open or normally closed. These are the terms given to the valves in their normal states. The 4-way valve switches supply between two outlet ports. The manually activated valves are operated with a foot pedal, handle, or knob to open to close them. The operator controls the valve and spring.

Solenoid operated valves use an electrical coil to open or close the valve by controlling the position of the plunger or spool. Air piloted valves use an external air source in a remote location. There is an internal air pilot system that provides a signal to control the larger valve spool.

14. What are the ports and positions in the pneumatic control valve?

The function of the valve is dependent on the ports and positions in the system. While choosing the valve, considering these options is very important. A 2-way port has one inlet and one outlet port with no way to vent air pressure. The pathways from where the air enters or leaves the valves are called ‘ways’, and different available states are called ‘positions’.  The pneumatic control valves that are commonly used in industries are 2, 3, or 4-way.

2 or 3-way valves have 2 positions while 4-way valve has 2 or 3 positions. If the third port is added, a 2-position valve can supply or exhaust pressure. For cylinder movement, exhausting pressure is important, 2 position valves are important in applications such as single-acting cylinders. If two more ports are added, it becomes 5 ports, which is technically a 4-way valve as two ports are open to exhaust. It is common in double-acting cylinders, with a range of control capabilities. In a 2-position configuration, the output flows from the inlet while the outlet port is flowing air to the exhaust port.

15. How is electric control valve different from pneumatic control valve?

The electric control valve has a compact structure and uses the motor as the power. You can connect them to various open networks and save wiring efforts. Electric control valves are not affected by climate and have a good effect on liquid medium. They are suitable in a system with large diameters because their switching speed is slow. It is a one-way valve, and when the closed valve is not powered, the spring pressing does not allow it to open.

On the other hand, the Pneumatic control valve uses compressed air instead of the motor as the power. It can work well on gas and a liquid medium with small diameters. Compared to the electric control valve, the pneumatic control valve is low cost with less maintenance. Pneumatic valves are faster than the electric valves, but electric valve has a simple structure.

16. What are pneumatic control valve configurations?

The pneumatic control valve offers two configurations. The first one is the variable restriction which has the components that control the pneumatic control valve. The variable restriction controls the valve by opening and closing it. One of the examples of this configuration is the needle valve. The second configuration is responsible for the direction of liquid flow in one direction. The check valve is an example of this configuration pneumatic control valve because it controls and restricts the flow in one direction.

The pneumatic control valve has various designs, styles, and configurations. You should purchase the type of configuration depending on your application. The level of application is an essential aspect in determining the valve required.

17. How to purchase the pneumatic control valve best for your application?

Purchasing the right pneumatic control valve for your business could be a daunting task.  There are various designs and options to choose from. You have to know various terminologies and techniques. If you are naïve with the basics of pneumatic control valves, you may end up choosing the wrong valve. The pneumatic control valve has various accessories and parts. They are an important part of the pneumatic control valve as they increase the reliability and service life of the pneumatic valve.

These accessories include electronic regulators, pressure regulators, and an air regulator valve. Also, there are various variations of ball valves in the pneumatic control valve. Normally, there are three standard ball valves. These balls include PSI ball valve, Ball valve stainless steel series, and cryogenic ball valves. The pneumatic control valves are suitable to work for various applications, including mining, aerospace, and military. These control valves are cost-effective and offer high performance.

18. What are the classifications of pneumatic valves?

The pneumatic control valve is classified into various groups based on its functions. The directional control valve manages to control the direction of flow in the pneumatic system. The directional control valves regulate the airflow and are responsible for starting and closing the airflow. The non-return valve controls the flow of air only in one direction while the other direction is blocked. Some non-return valves that do the pneumatic control are the check valve, two pressure valves, and quick exhaust valves.

The flow control valve regulates airflow, but the control action is limited to the airflow. The pressure control valve controls valve pressure and air pressure in the valve. The pressure control valve is further classified into pressure limiting valve, pressure reducing valve, and pressure sequence valve.

19. How to calibrate a pneumatic control valve actuator?

The pneumatic control valve calibration process is manual. The calibration is started when the pneumatic positioner receives a signal between 3 and 15 psi. First, you need to install the positioner on the valve, connect it with the valve actuator and connect the air supply.

Set the control valve into zero position and adjust the span. Do back and forth between zero and span and ramp up the valve’s travel using 4, 8, 12, 16, and 20mA.

Conclusion

The pneumatic control valve controls and modulates the flow of fluid in a pneumatic system. The valve uses air as a controlled mechanism, and the media flowing through the valve ports is water, oil, or any other fluid. Hence, the pneumatic control valve controls the flow of fluid and acts as a control media to provide flow control in the valve.

If you want to purchase a pneumatic control valve for your application, contact our team of experts at Instruthink. We will provide you best assistance in guiding and selecting the pneumatic control valve that is a perfect fit for your needs. You can contact us at sales@instruthink.com or directly call us on +44 7700 307784. We will be there for our customers 24/7.