Basic parameter setting of the electric device of the valve
The realization of remote control, automatic control and remote control of the valve is inseparable from the electric device of the valve, and the electric device of the valve also has some basic parameters of its own. Its movement process is influenced by several factors:Stroke, Torque or Axial Thrust.The type of valve, the working specification of the device and the position of the valve on the pipeline or equipment affect theThe utilization rate of the valve electric device andWorking characteristics.
Valve Electric Actuator
The electric device generally consists of the following parts:
The special motor is characterized by strong overload capacity, large starting torque, small moment of inertia, and short-term and intermittent work.
The reduction mechanism is used to reduce the output speed of the motor.
The stroke control mechanism is used to adjust and accurately control the opening and closing position of the valve.
The torque limiting mechanism is used to adjust the torque (or thrust) and keep it from exceeding a predetermined value.
Manual and electric switching mechanism, interlocking mechanism for manual or electric operation.
The opening indicator is used to show the position of the valve during opening and closing.
1. Select the electric actuator according to the valve type
1.Quarter stroke electric actuator (corner
The rotation of the output shaft of the electric actuator is less than one cycle, that is, less than 360 degrees, usually 90 degrees to realize the opening and closing process control of the valve. This type of electric actuator is divided into two types: direct connection type and base crank type according to the different installation interface methods.
a) Direct connection type: refers to the form in which 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 turn, that is, more than 360 degrees. Generally, it takes multiple turns to realize the opening and closing process control of the valve.
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 rotary.
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 electric actuators generally control the opening or closing of the valve. The valve is either in the fully open position or 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 also be divided into split structure and integrated structure due to different structural forms. This must be explained when selecting a model, otherwise, mismatches such as conflicts with the control system during on-site installation often occur.
a) Split structure (commonly referred to as ordinary type): the control unit is separated from the electric actuator, and 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 for control. matching.
The disadvantage of this structure is that it is not convenient for the overall installation of the system, increases wiring and installation costs, and is prone to failure. When a failure occurs, it is not convenient for diagnosis and maintenance, and the cost performance is not ideal.
b) Integrated structure (usually referred to as integral type): the control unit and the electric actuator are packaged into one body, which can be operated on the spot without an external control unit, and can be operated remotely only by outputting relevant control information.
The advantage of this structure is that it facilitates the overall installation of the system, reduces wiring and installation costs, and is easy to diagnose and troubleshoot. However, the traditional integrated structure products also have many imperfections, so intelligent electric actuators have been produced.
2. Modulating type (closed loop control)
The adjustable electric actuator not only has the function of an on-off integrated structure, but also can precisely control the valve and adjust the flow of the medium.
a) Control signal type (current, voltage)
The control signal of the adjustable electric actuator generally has a current signal (4~20mA, 0~10mA) or a voltage signal (0~5V, 1~5V), and the control signal type and parameters need to be specified when selecting the model.
b) Working form (electric open type, electric close type)
The working mode of the adjustable electric actuator is generally the electric open type (taking the control of 4 ~ 20mA as an example, the electric open type means that the 4mA signal corresponds to the valve close, and the 20mA corresponds to the valve open), and the other is the electric close type. (Taking 4-20mA control as an example, the electric open type means that the 4mA signal corresponds to the valve opening, and the 20mA signal corresponds to the valve closing).Wear-resistant welding rod
c) Loss of signal protection
Loss of signal protection means that when the control signal is lost due to faults such as lines, 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 maintain the original position.
3. Electric devices classified according to the use environment and explosion-proof level
According to the use environment and explosion-proof grade requirements, the electric device of the valve can be divided into ordinary type, outdoor type, explosion-proof type, outdoor explosion-proof type, etc.
Determine the output torque of the electric actuator according to the torque required by the valve
The torque required for valve opening and closing determines how much output torque the electric actuator chooses. Generally, it is proposed by the user or selected by the valve manufacturer. As the actuator manufacturer is only responsible for the output torque of the actuator, the valve required for normal opening and closing The torque is determined by the valve caliber size, working pressure and other factors, but due to the difference in processing precision and assembly process of valve manufacturers, the torque required for valves of the same specification produced by different manufacturers is also different, even for the same valve manufacturer produced by the same valve manufacturer. The torque of the standard valve is also different. When the torque of the actuator is too small when selecting the model, it will cause the valve to fail to open and close normally. Therefore, the electric actuator must choose a reasonable torque range.
The above is the basic parameter setting of the valve electric device shared with you today. If you have relevant needs, please read the above, I believe it will be of great help.