Key considerations for valve actuator selection (3)

Determine the control mode of the electric actuator according to the production process control requirements. The control modes of electric actuators are generally divided into two categories: switch type (open loop control) and regulation type (closed loop control).

1. Switch 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 the color quartz tube level gauge is in the fully closed position. This type of 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.

1. 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.

2. Integrated structure (usually called integral type): The control unit and the electric actuator are packaged as one, and can be operated on the spot without external control unit, and 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, the traditional stainless steel solenoid valve integrated structure product also has many imperfections, so the intelligent electric actuator has been produced. The intelligent electric actuator will be explained later.

2. Regulating type (closed loop control)

　　Adjustable electric actuator not only has a switch-type integrated structure but also accurately adjusts the medium flow. Because of its function, it can also accurately control the valve. Since space is limited, its working principle will not be explained in detail here. The following is a brief description of the parameters that need to be noted when selecting the adjustable electric actuator.

1. Control signal type (current, voltage)

Regulating electric actuator control signals generally include current signals (4～20mA, 0～10mA) or voltage signals (0～5V, 1～5V). The type and parameters of the control signal must be clarified when selecting the model.

2. Working form (electric open type, electric close 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 valve opening), and the other is electric closing type (Take the 4-20mA control as an example, the electric opening type means that the 4mA signal corresponds to the valve opening, and the 20mA corresponds to the valve closing.) Generally, the selection needs to clarify the working form, and many products cannot be modified after they leave the factory. , The intelligent electric actuator produced by Ogilvy Valve Control can be modified at any time through on-site settings.

3. 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 of the magnetic tilt column level gauge are fully open, fully closed, and remain in place Three cases, and it is not easy to modify after leaving the factory. The intelligent electric actuators produced by Ogilvy Valve can be flexibly modified through on-site settings, and any position (0~100%) can be set as the protection value.