Control valve actuator selection
Jun 26, 2019| Control valve actuator selection
In order for the regulating valve to work properly, the actuator used should generate sufficient output force to ensure a high degree of sealing and opening of the valve.
For double-acting pneumatic, hydraulic, and electric actuators, there is generally no return spring. The magnitude of the force is independent of its direction of travel. Therefore, the key to selecting an actuator is to clarify the large output force and the rotational torque of the motor. For a single-acting pneumatic actuator, the output force is related to the opening of the valve. The force appearing on the regulating valve will also affect the motion characteristics. Therefore, it is required to establish a force balance across the opening range of the regulating valve.
Determination of the type of actuator
After determining the output force of the actuator, select the corresponding actuator according to the requirements of the process environment. For explosion-proof requirements on site, pneumatic actuators should be used. In terms of energy saving, electric actuators should be selected as much as possible. If the adjustment accuracy is high, the hydraulic actuator can be selected. Such as the speed regulation of the power plant transparent machine, the temperature regulation control of the refinery's catalytic device reactor.
The mode of action of the regulating valve
The mode of action of the regulating valve is only when the pneumatic actuator is selected, and its action mode is formed by the combination of the positive and negative action of the actuator and the positive and negative action of the valve. There are 4 kinds of combination forms, namely, positive (gas-off type), positive and negative (air-open type), anyway (air-open type), and reverse-reverse (air-closed type). The regulating valve formed by these four combinations has a gas function. Open and gas two. The choice of the mode of operation of the regulating valve is mainly considered from three aspects: a) process production safety; b) medium characteristics; c) product quality assurance, low economic loss