How to choose electric actuator

How to choose electric actuator

　　Electric actuator is an indispensable driving device to control the valve. Its movement process can be controlled by the stroke, torque or axial thrust. The working characteristics and utilization of valve electric actuators are determined by many factors, but mainly depends on the type of solenoid valve, the working specifications of the device and the position of the valve on the pipeline or equipment.

1. Choose electric actuator according to valve type

        1. The angular stroke electric actuator (rotation angle "360 degrees) is suitable for butterfly valves, ball valves, plug valves, etc. The rotation of the output shaft of the electric actuator is less than one revolution, that is, less than 360 degrees, usually 90 degrees to achieve the valve opening and closing process control. This kind of electric actuator is divided into direct connection type and base crank type according to the different installation interface methods.

A) Direct-connected type: refers to the form where the output shaft of the electric actuator is directly connected to the valve stem.

B) Base crank type: refers to the form in which the output shaft is connected to the valve stem through a crank.

2. Multi-turn electric actuators (rotation angle "360 degrees) are suitable for gate valves, globe valves, etc. The rotation of the output shaft of the electric actuator is more than one circle, that is, more than 360 degrees. Generally, it takes more than one circle to realize the valve opening and closing process control.

3. Straight stroke (linear motion) is suitable for single-seat control valves, double-seat control valves, etc. The motion of the output shaft of the electric actuator is linear motion, not rotating.

2. Determine the control mode of the electric actuator according to the production process control requirements

1. On-off type (open-loop control) On-off type electric actuators generally realize the on or off control of the valve. The valve is either in the fully open position or in the fully closed position. This type of gas solenoid valve does not require precise control of the medium flow. . It is particularly worth mentioning that switch-type electric actuators can be divided into split structure and integrated structure due to different structural forms. This must be explained when selecting the model, otherwise mismatches such as conflicts with the control system during on-site installation will often occur.

A) Split structure (usually called ordinary type): The control unit is separated from the electric actuator. The electric actuator cannot control the valve alone. It must be controlled by an external control unit. Generally, the external controller or control cabinet is used. Matching. The disadvantage of this structure is that it is inconvenient for the overall installation of the system, increases wiring and installation costs, and is prone to failure. When a failure occurs, it is not easy to diagnose and repair, and the cost performance is not ideal.

B) Integrated structure (usually called integral type): The control unit and the electric actuator are packaged into one body, and it can be operated on the spot without external control unit. It can be operated remotely only by outputting relevant control information. The advantage of this structure is to facilitate the overall installation of the system, reduce wiring and installation costs, and facilitate diagnosis and troubleshooting. However, traditional integrated structure products also have many imperfections, so intelligent electric actuators are produced.

2. Regulating (closed loop control) Regulating Electric Actuator not only has the function of an on-off integrated structure, but also can accurately control the valve and adjust the medium flow.

A) Type of control signal (current, voltage) Regulating electric actuator control signal generally includes current signal (4～20MA, 0～10MA) or voltage signal (0～5V, 1～5V), and its control should be clarified when selecting type Signal type and parameters.

B) Working form (electric opening type, electric closing type) The working mode of the regulating electric actuator is generally electric opening type (take 4～20MA control as an example, electric opening type means that 4MA signal corresponds to valve closing, 20MA corresponds to The one is valve opening), the other is the electric closing type (take 4-20MA control as an example, the electric opening type means that the 4MA signal corresponds to the valve opening, and the 20MA signal corresponds to the valve closing).

C) Loss of signal protection Loss of signal protection means that when the control signal is lost due to line faults, the electric actuator will open and close the control valve to the set protection value. The common protection values are fully open, fully closed, and keep in place. This situation.

Third, the torque of the actuator

Determine the output torque of the electric actuator according to the torque required by the high temperature solenoid valve. The torque required for the normal opening and closing of the valve is determined by the valve diameter, working pressure and other factors, but the valve manufacturer's processing accuracy and assembly process are different, so it is different The torque required for the valves of the same specification produced by the manufacturer is also different. Even the torque of the same specification valve produced by the same valve manufacturer is also different. When the torque of the actuator is selected too small, the valve cannot be opened and closed normally, so electric The actuator must select a reasonable torque range.

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