How to Choose the Spring Range of Pneumatic Actuator Reasonably?

 

In fact, it is understood that pneumatic actuators include spring return actuator, pneumatic rotary vane actuator and pneumatic rack and pinion actuator.

 

The so-called design spring range of the pneumatic film actuator refers to the part parameters when we design and produce the spring. When working, corresponding adjustments should be made according to the air opening and closing of the regulating valve, which we call the working spring range.

 

This article takes the design spring range of 20～100KPa as an example. For the air-closed control valve, we can adjust the working spring range to 10～90KPa, so that 10 KPa acts on the effective area Ae of the membrane chamber. Another example is the air opening regulating valve, which opens with air, and closes when there is no air. At this time, the pressure difference is overcome by the spring's pre-tightening force. In order to overcome the larger pressure difference, it is necessary to tighten the pre-tightening force and also need to bring a positioner. If the air source of the positioner is 140KPa, we can tighten the design spring range from 20～100KPa to 50～130KPa, and the output force is 50KPa×Ae. If 20～100KPa is fixed as a standard spring, it will only be 20KPa×Ae, and the belt retainer will not work. It can be seen that the air valve with positioner must also increase the starting pressure of the spring range to increase the output force of the actuator.

 

For occasions without positioner, we can also design 20～80KPa for air-closed control valve and pneumatic gate valve, so that there is still an output force of 20KP.Ae without positioner. Therefore, the range of the spring should be based on the air opening/closing, with or without a locator, and the direction of the unbalanced force generated by the pressure difference. Only when the three are combined can a suitable spring be designed.

 

Reasonably Choose the Spring Range of the Pneumatic Actuator

 

The selection of the spring range of the pneumatic actuator is mainly considered from the two aspects of the stability of the regulating valve and the output force. Pneumatic actuators related to the spring concept can be divided into spring return pneumatic actuator and double acting spring return actuator.

 

1. Choose from the stability of the regulating valve, the spring should be as hard as possible. If the spring of 40～200 KPa, 60～180KPa is selected, it can not only overcome slight oscillation and friction, but also make the valve core move back and forth freely.

 

2. Since the output force of the actuator is the total force of the actuator minus the tension and friction of the spring, the softer the spring is, the greater the output force is. Therefore, considering the output force, a soft spring (that is, a small spring range) should be selected.

 

3. If you choose from the standpoint of stability, choose a hard spring with a large spring range. From the perspective of output force, a soft spring with a small spring range should be used. The two are contradictory to each other, so they should be considered comprehensively. In the case of meeting the output force, try to choose a hard spring with a large range. The above factors will be considered when choosing compact pneumatic actuator and rotary piston actuator.

 

4. In case of large diameter, large pressure difference, particles, etc., the selection of the spring range can meet the needs through detailed calculations.