The type of valve is quite a lot, the working principle is not quite the same, in general to turn the valve plate Angle, lifting valve plate and other ways to achieve open and close control, when supporting the electric actuator should first according to the type of the valve to choose electric actuator.
Key considerations for valve driving device selection
A, Select electric actuator according to valve type
The type of valve is quite a lot, the working principle is not quite the same, in general to turn the valve plate Angle, lifting valve plate and other ways to achieve open and close control, when supporting the electric actuator should first according to the type of the valve to choose electric actuator.
1. Angular travel electric actuator (Angle <360 degrees)
The rotation of the output shaft of the electric actuator is less than one week, that is, less than 360 degrees, usually 90 degrees to achieve the opening and closing process control of the valve. This type of electric actuator can be divided into two types according to the different installation interface mode: directly connected type and base crank type.
A) Directly connected type: refers to the type of direct connected installation of the output shaft of the electric actuator and the valve stem.
B) Base crank type: means the form in which the output shaft is connected to the valve stem by a crank.
This kind of electric actuator is suitable for butterfly valve, ball valve, plug valve and so on.
2. Multi-turn electric actuator (Angle >360 degrees)
The rotation of the output shaft of the electric actuator is greater than one cycle, that is, more than 360 degrees. It generally takes more than one turn to realize the control of the opening and closing process of the valve.
This type of electric actuator is suitable for gate valves, globe valves, etc.
3. Straight stroke electric actuator (linear motion)
The motion of the output shaft of the electric actuator is linear motion, not rotational form.
This kind of electric actuator is suitable for single seat control valve, double seat control valve and so on.
Second, according to the production process control requirements to determine the control mode of electric actuator
The control modes of electric actuators are generally divided into two categories: switching type (open-loop control) and regulating type (closed-loop control).
1. Switch type (open loop control)
The switch type electric actuator generally realizes the control of the valve on or off, the valve is either in the full open position, or in the full close position, this kind of valve does not need to carry on the precise control to the medium flow rate.
It is worth mentioning that the switch type electric actuator can be divided into two parts because of the different structure form and the integrated structure. This must be explained in the selection, or it will often occur in the field installation and control system conflict mismatch.
A) Split structure (commonly referred to as the common type) : the control unit is separated from the electric actuator. The electric actuator cannot control the valve independently, and the control unit must be added to realize the control. Generally, the external controller or control cabinet is used to form a complete set.
The disadvantages of this structure are that it is not easy to install the system as a whole, increase wiring and installation costs, and is prone to failure. When the fault occurs, it is not easy to diagnose and maintain, and the cost performance is not ideal.
B) Integrated structure (commonly referred to as integral type) : the control unit and the electric actuator are encapsulated as one. No external control unit is needed to operate in place and remote control can be operated only by outplacing relevant control information.
The advantages of this structure are that it facilitates the whole system installation, reduces wiring and installation costs, and is easy to diagnose and troubleshoot. But the traditional integrated structure products also have many imperfect places, so the generation of intelligent electric actuator, about the intelligent electric actuator will be explained later.
2. Regulating type (closed loop control)
The adjustable electric actuator not only has a switch type integrated structure but also accurately regulates the medium flow. As a result of the function, it can also be accurate control of the valve, from the limited space of its working principle is not described in detail here. The following is a brief description of the parameters to be indicated in the selection of adjustable electric actuators.
A) Type of control signal (current, voltage)
The control signals of regulating electric actuators generally include current signals (4 ~ 20mA, 0 ~ 10mA) or voltage signals (0 ~ 5V, 1 ~ 5V). The type and parameters of the control signals shall be specified in the selection.
B) Working mode (power on, power off)
The operating mode of regulating electric actuators is generally electric open type (taking control of 4-20mA as an example, electric open type refers to valve closing corresponding to 4mA signal and valve opening corresponding to 20mA), and the other is electric close type (taking control of 4-20mA as an example, electric open type refers to valve opening corresponding to 4mA signal and valve closing corresponding to 20mA). In general, the type of work needs to be clear, many products can not be modified after leaving the factory, Ogilvy valve control production of intelligent electric actuator can be modified at any time through the site setting.
C) Loss of signal protection
Loss of signal protection means that when the control signal is lost due to circuit faults, the electric actuator opens and closes the control valve to the set protection value. The common protection value is fully open, fully closed, and kept in place, which is not easy to be modified after leaving the factory. The intelligent electric actuators produced by Ogilvy valve Control can be flexibly modified through field setting, and can be set at any position (0~100%) as the protection value.
Three, according to the valve required torque to determine the output torque of the electric actuator
Valve opening and closing the required torque determines the output torque of electric actuator to choose how, generally is put forward by the user or by matching valve manufacturer, as the actuator manufacturer is only responsible for the output torque of actuators, normal valve opening and closing the required torque is determined by the valve diameter size, factors such as work stress, but because of the valve manufacturer processing precision, the assembly process, so that different manufacturer production of the same specification valve required torque is also different, even with a valve manufacturer production with specification valve torque is different also, was elected type actuator torque choice is too small will cause can’t normal open/close the valve, Therefore, the electric actuator must choose a reasonable torque range.
Four, according to the selected electric actuator to determine the electrical parameters
Because of different actuators manufacturer of electrical parameters is different, so the model selection of the design is generally to determine its electrical parameters, main motor power, rated current, secondary voltage control circuit and so on, tend to neglect in this regard, the control system does not match with the electric actuators cause the work in time and space trip, blown fuse, thermal overload relay protection jump faults such as like now.
Five, according to the use of the choice of shell protection grade, explosion-proof grade
1. Shell IP protection class 2. Explosion protection class
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