AT Pneumatic Actuator Double-acting Pneumatic Actuator Pneumatic Ball Valve Butterfly Valve Special Actuator

► Technical data

Double acting actuator

The selection of double-acting actuators takes DA series pneumatic actuators as an example. The output torque of the rack-and-pinion actuator is obtained by multiplying the piston pressure (supplied by the air source pressure) by the pitch circle radius (force arm), as shown in Figure 4. And the friction resistance is small and the efficiency is high. As shown in Figure 5, the output torque is linear for both clockwise and counterclockwise rotations. Under normal operating conditions, the recommended safety factor for double-acting actuators is 25-50%

single acting actuator

The selection of Mingjing single-acting actuators takes SR series pneumatic actuators as an example. In the application of spring return, the output torque is obtained in two different operation processes. According to the stroke position, each operation generates two different torque values. . The output torque of the spring return actuator is obtained by multiplying the force (air pressure or spring force) by the force arm. In this case, the air source pressure forces the piston to turn from 0 degrees to 90 degrees. Due to the reaction force generated by the compression of the spring, the torque gradually decreases from the maximum value at the starting point until it reaches the second situation: the output torque is that the spring recovers when the middle cavity loses air. The force acting on the piston is called “spring stroke output torque”. In this case, due to the elongation of the spring, the output torque gradually decreases from 90 degrees to 0 degrees. As mentioned above, the single-acting actuator is based on two It is designed on the basis of generating a balance moment under such conditions. As shown in Figure 11. In each case, by changing the relationship between the number of springs per side and the air supply pressure (eg 2 springs per side and 5.5 bar air supply or vice versa) it is possible to obtain an unbalanced moment. In spring return applications two conditions can be obtained : On loss of air or off on loss of air. Under normal operating conditions, the recommended safety factor for spring return actuators is 25-50%

Selection examples for spring return actuators (see also technical data sheet):

Spring closed (out of air)

*Torque of ball valve=80NM

*Safety factor (25%)=80NM+25%=100NM

*Air source pressure=0.6MPa

The SY-SR actuator chosen was the SR125-05 because the following values ​​were produced:

*Spring stroke 0o=119.2NM

*Spring stroke 90o=216.2NM

*Air stroke 0o=228.7NM

*Air stroke 90o=118.8NM

► Features

In terms of technical performance, the advantages of pneumatic actuators mainly include the following four aspects:

(1) The load is large, which can adapt to the application of high torque output.

(2) Quick action and quick response.

(3) Good adaptability to the working environment, especially in harsh working environments such as flammable, explosive, dusty, strong magnetism, radiation and vibration, it is superior to hydraulic, electronic and electrical control.

(4) The motor is easily damaged when the stroke is blocked or the valve stem is tied.

The advantages of electric actuators mainly include:

(1) Compact structure and small size. Compared with pneumatic actuators, electric actuators are relatively simple in structure. A basic electronic system includes the actuator, a three-position DPDT switch, a fuse and some wires, which are easy to assemble.

(2) The drive source of the electric actuator is very flexible. Generally, the on-board power supply can meet the needs, while the pneumatic actuator needs an air source and a compression drive device.

(3) Electric actuators have no danger of “air leakage” and have high reliability, while the compressibility of air makes pneumatic actuators slightly less stable.

(4) There is no need to install and maintain various pneumatic pipelines.

(5) The load can be maintained without power, while the pneumatic actuator requires a continuous pressure supply.

(6) The electric actuator is quieter because no additional pressure device is required. Usually, if the pneumatic actuator is under heavy load, a silencer should be installed.

(7) In pneumatic devices, it is usually necessary to convert electrical signals into gas signals, and then into electrical signals. The transmission speed is slow, and it is not suitable for complex circuits with too many components.

(8) Electric actuators are superior in control accuracy.