Imported pneumatic ball valve is a widely used type of automatic control valve. It is characterized by fast switching action, good sealing, low resistance and large flow capacity. Convenient remote control, fire and explosion-proof. Equipped with a solenoid valve as a pilot valve, it is convenient to remotely control the piston in the pneumatic actuator to rotate 90°C to drive the ball core switch action. Equipped with a travel switch, the switching signal can be fed back to the instrument control room to understand the valve switching status in real time. When the solenoid valve coil is damaged, the control instrument will give a valve switching signal. When the pneumatic ball valve does not move, the travel switch can know If the valve does not actually move, the solenoid valve can be inspected in time to eliminate the fault.
Imported pneumatic ball valve is composed of pneumatic actuator and ball valve. The pneumatic actuator is the execution part through which the control signal controls the opening and closing of the ball valve.
1. There is a return spring in the single-acting pneumatic actuator, which together with the ball valve forms a single-acting pneumatic ball valve. It can automatically reset when there is no compressed air. Single-acting pneumatic ball valves are required in key process control parts. They can form interlock control with solenoid valves to cut off pipelines in time to ensure the safety of production equipment.
2. There is no return spring in the double-acting pneumatic actuator. It remains in place when there is no compressed air and cannot make actions that are beneficial to process safety. It is used in places where the control switch status is not important. When an air source failure occurs , double-acting pneumatic ball valves can be selected when the opening or closing of the pneumatic ball valve will not cause adverse effects on the control system.
3. When a single-acting pneumatic ball valve is equipped with a ball valve of the same caliber, the cylinder diameter must be increased, and a return spring must be installed inside. The cost is higher than that of a double-acting pneumatic ball valve. Cost and demand must be considered comprehensively when selecting. Pneumatic actuators are divided into double-acting and single-acting. Single-acting pneumatic actuators (there is a spring inside the actuator. When the air source is lost, the spring will automatically reset and provide force to return the ball valve to its original open or closed state). If you choose a double-acting pneumatic actuator, when the air source is lost, the pneumatic actuator will lose power, and the valve position will remain at the position it was at the moment it lost air. So, if you need the valve to automatically reset when it loses air, choose a single-acting pneumatic actuator. If not, choose a double-acting pneumatic actuator.
The difference between single-acting pneumatic ball valves and double-acting pneumatic ball valves is that there is a spring in the single-acting cylinder, but there is not in the double-acting one. The single-acting one is divided into air-opening and air-closing. There are two types of air source protection functions, and the double-acting one has a gas source protection function. Then the air source is cut off and kept in place.
In terms of price, the price differs according to the size of the cylinder. If it is small, the price difference is not too big. If it is large, the single-acting one will be more expensive.
Single action: One side of the cylinder piston is a spring and the other side is an instrument air. ——When this kind of valve stops the instrument air flow, the piston will be driven by the spring force to fully close or fully open the valve.
Double-action: There is no spring in the cylinder, and both sides of the piston are filled with instrument air. This type of valve itself has no terms of air opening and air closing. The opening of the air stop valve remains in its original position.
The double-acting pneumatic actuator starts to rotate and open the valve when it is ventilated. When the valve is to be closed, the other side is ventilated to close it. It is reset by the cylinder and can only stay in place when the air source is lost;
The single-acting pneumatic actuator opens the valve when ventilation is provided, and automatically closes when the air source is not supplied. The single-acting pneumatic actuator automatically resets by a spring. It is generally used in dangerous working conditions, such as transporting flammable valves. For gases or flammable liquids, when the gas source is lost and an emergency occurs, the single-acting pneumatic actuator can automatically reset to minimize the risk, while the double-acting actuator is generally not easy to reset.
Single-acting pneumatic actuators are generally divided into normally open and normally closed types.
Normally open type: ventilation closed, air shut-off open
Normally closed type, ventilation open,
In general working conditions, double-acting gas shutoff switches are mostly used. Double-acting cylinders do not have springs, so the cost is lower than single-acting pneumatic actuators.