Application Fields of Pneumatic Valves

Pneumatic valve is a device that uses compressed air as a power source to drive the valve to open, close or regulate fluid flow, and is widely used in the industrial field.

The structural composition of pneumatic valves

pneumatic actuator

This is the core component of pneumatic valves, which converts the pressure energy of compressed air into mechanical energy. There are two common types of pneumatic actuators: diaphragm type and piston type. The membrane actuator has a simple structure and is easy to maintain. It drives the valve stem movement through the elastic deformation of the membrane sheet. For example, in some small pneumatic globe valves, membrane actuators can effectively achieve valve opening and closing operations. Piston actuators have a higher output force and are suitable for valves with large diameters or high pressures. The piston moves inside the cylinder and can generate a large thrust to drive the valve stem. For example, in large pneumatic ball valves, piston actuators can ensure that the valve works normally under high pressure differentials.

Valve body

This part is similar to ordinary valves, and there are various types of valve bodies according to different purposes and media. For example, the body of a pneumatic ball valve is a spherical valve core, which connects or disconnects the through-hole on the ball with the pipeline through the rotation of the valve stem. The body of a pneumatic butterfly valve is a butterfly shaped valve plate, which rotates around an axis to control the flow of fluid. The valve body also includes components such as the valve body, valve seat, and sealing ring. The valve body is the outer shell of the valve, which plays a role in containing fluids and fixing other components; The valve seat is the part that cooperates with the valve core to form a sealing surface; Sealing rings are used to prevent fluid leakage, and common sealing ring materials include rubber, polytetrafluoroethylene, etc.

connecting member

It connects the pneumatic actuator with the valve body. Usually, threaded connections, flange connections, and other methods are used. Threaded connections are suitable for small pneumatic valves and are easy to install and disassemble. Flange connection is used for large-diameter or high-pressure pneumatic valves. It firmly connects the actuator and valve body together through flanges and bolts, ensuring that they will not loosen during operation.

Working principle of pneumatic valve

Activate action

When compressed air enters the cylinder side of the pneumatic actuator (for piston actuators) or the diaphragm chamber of the diaphragm actuator (for diaphragm actuators), the air pressure pushes the piston or diaphragm to move. The piston or diaphragm drives the valve core of the valve body (such as the ball of a ball valve, the butterfly plate of a butterfly valve, etc.) to move or rotate through the valve stem, causing the valve to change from a closed state to an open state. For example, in a pneumatic gate valve, compressed air enters the actuator and pushes the valve stem upwards, causing the gate to rise and the fluid channel to open.

Close Action

The action of closing the valve is the opposite process of the action of opening. When the gas on the other side of the actuator is discharged, the elastic force of the spring (if there is a spring inside the actuator) or the pressure on the other side causes the piston or diaphragm to move in the opposite direction, and the valve core returns to the closed position. Taking the pneumatic globe valve as an example, when the gas supply to one side of the actuator is stopped, the air pressure or spring force on the other side causes the valve stem to move downward, and the valve core and valve seat are tightly fitted, cutting off the fluid channel.

Adjustment function (for adjustable pneumatic valves)

Some pneumatic valves have regulating functions, such as pneumatic control valves. It adjusts the opening of the valve core by changing the input pressure of compressed air or controlling the stroke of the pneumatic actuator, thereby achieving precise control of fluid flow. For example, in chemical production, the feeding amount of raw materials in the reaction kettle is controlled by adjusting the opening of the pneumatic control valve to ensure the normal progress of the reaction.

Advantages of Pneumatic Valves

High safety

The power source of pneumatic valves is compressed air, which is itself pollution-free. Even in some flammable and explosive environments, as long as the pressure and flow rate of the air are controlled properly, there is no possibility of electrical sparks causing danger like electric valves. For example, in the process of petroleum refining, pneumatic valves are widely used in pipelines for transporting flammable liquids, avoiding potential safety hazards that may arise from electrical equipment.

Fast response speed

The transmission speed of compressed air is fast, and the action of pneumatic actuators is also fast. After the control signal (such as the on/off of the solenoid valve) is issued, the valve can complete the opening or closing action in a short time. This is very suitable for situations that require quick switching of fluid flow, such as in material conveying systems on automated production lines, where pneumatic valves can quickly respond to control signals to ensure production continuity.

Low maintenance cost

The structure of pneumatic valves is relatively simple, without complex electrical components. Its main components such as pneumatic actuators and valve bodies have a low failure rate, and professional electrical knowledge is not required for maintenance. For example, if a thin film pneumatic actuator malfunctions, it usually only needs to replace simple components such as the film sheet to restore normal operation, and the maintenance cost and time are relatively low.

Disadvantages of Pneumatic Valves

Need gas source

Pneumatic valves must be equipped with a compressed air source, which increases the complexity and cost of the equipment. A series of equipment such as air compressors, air storage tanks, and filters need to be installed to provide stable compressed air. Moreover, in some remote areas or places without suitable gas sources, the use of pneumatic valves may be restricted.

Limited output force (relative to electric valves)

Although the output force of piston type pneumatic actuators is relatively large, compared with high-power electric actuators, the output force of pneumatic actuators may be slightly inferior at the same size. This makes it possible that pneumatic valves may not be able to meet the requirements in situations where extremely high torque is needed to drive large valves.

Application fields of pneumatic valves

Chemical industry

Used for transporting various chemical media such as acids, bases, organic solvents, etc. Pneumatic valves have good corrosion resistance and can be adapted to different chemical media by selecting appropriate valve materials (such as stainless steel, plastic, etc.). For example, in the production process of sulfuric acid, pneumatic valves are used to control the transportation of sulfuric acid and the flow of materials during the reaction process.

Food industry

Due to the good cleanliness of pneumatic valves, they do not cause contamination to food and are commonly used for conveying liquid, semi fluid, and powder materials in food processing. For example, in beverage production lines, pneumatic valves are used to control the addition and transportation of liquids such as syrup and juice.

Pharmaceutical industry

In the process of drug production, pneumatic valves are used to control the transportation of drugs, the feeding and discharging of reaction vessels, and other links. It can ensure the hygiene requirements of drug production while achieving automated control.

Water Treatment Industry

Used to control the flow direction, flow rate, etc. of water. For example, in sewage treatment plants, pneumatic valves can control operations such as sewage diversion and sludge transportation.