Valve electric device is driven equipment valve control, automatic control and remote control is indispensable, and its movement can be stroke, torque or to control the size of the axial thrust. Because the job specification device and valve type, valve actuators of the operating characteristics and utilization depends on the valve in the pipeline or equipment location.
Electric device generally consists of the following parts:
Special motor, is characterized by strong overload capacity, large starting torque, small moment of inertia, short-term, intermittent working.
Reduction mechanism, to reduce the motor's output speed.
Stroke control mechanism, used to open and close position to regulation and precise control of valve.
Torque limit agencies, to adjust torque (or thrust) and make no more than a predetermined value.
Manual, electric switching mechanism, interlocking mechanism of manual or electric operation.
Opening indicator is used to show, opening and closing the valve in the process of location.
According to the type of valve electric actuator selection
1 rotary electric actuator (angle <360 degrees) for butterfly valves, ball valves, plug valves.
Actuator output shaft rotation is less than a week, that is less than 360 degrees, usually for the opening and closing process control 90 degrees to achieve the valve. This kind of electric actuator according to different ways of installing the interface is divided into direct-attached, base crank two. Dedecms.com
A): refers to the form of direct connection type electric actuator output shaft and the valve stem straight.
B) base crank type: refers to the form of the output shaft is connected via a crank and rod.
Multi-turn electric actuator (angle >360 degrees) applied to gate valve, globe valve.
Actuator output shaft rotation more than a week, that is greater than 360 degrees, usually need to open and close the process control to achieve multi-turn valves.
Straight stroke (linear motion) for single-seat valve, double seat control valve.
Actuator output shaft motion into linear motion type, not turn the form.
According to production process control requirements to determine the control mode of electric actuator
Switch (open loop control)
General electric actuator switch to open or close the valve control, the valve or in a fully open position, or in a fully closed position, these valves do not need precise control on the media flow.
It is particularly worth mentioning is the switching electric actuator for the different structure form can also be divided into structure and integrated structure. Selection of the time required to make this description, or often in the on-site installation and control system does not match the conflict is like.
A) split structure (often referred to as the common type): the control unit and the electric actuator, electric actuator alone cannot achieve the control of the valves, the necessary external control unit to achieve control, external form of the controller and the control cabinet series. Content from dedecms
The disadvantage of this structure is not easy to install the whole system, increase the wiring and installation costs, and prone to failure, when a fault occurs is not easy to diagnose and repair, the price is not ideal.
B) integration structure (often referred to as the whole body): the control unit and the electric actuator package as a whole, no external control unit can be realistic in situ operation, remote output only related control operation can be carried out on the.
This structure is convenient to install the whole system, reduce the wiring and installation costs, easy diagnosis and troubleshooting. But the integration of traditional structured products, also has many imperfect places, so the intelligent electric actuator.
Regulation of type (closed-loop control)
Regulating electric actuator not only has the switch type integrated structure function, can carry on the precise control of the valve, regulating media flow.
A) control signal types (current, voltage)
Regulating electric actuator control signal current signal (4 ~ 20mA, 0 ~ 10mA) or voltage signal (0 ~ 5V, 1 ~ 5V), selection needs to make clear its control signal types and parameters.
B) forms of work (electric open type, electric type)
Regulating electric actuator for the electrical work normally open type (4 ~ 20mA control as an example, open the type is 4mA signal corresponding to the valve off, 20mA corresponds to the valve open), another is power off type (with 4-20mA control, for example, open the type is 4mA signal corresponding to the valve open, 20mA corresponds to the valve off). Electrode wear
C) loss of signal to protect the contents from dedecms
Loss of signal protection refers to the control signal loss caused by line fault, electric actuator will control the valve opening and closing to the set value of protection, the protection of common value is open, closed, remained in three cases.
According to the electric device using environment and explosion-proof grade classification
According to the use of the environment and explosion-proof requirements, the valve electric device can be divided into ordinary type, outdoor type, explosion-proof type, outdoor flameproof etc..
The output torque of the valve electric actuator is determined according to the required torque
The valve opening and closing the required torque determines the electric actuator output torque large, generally by the user puts forward or valve manufacturers to match, be responsible for the actuator manufacturers only in the actuator output torque, the valve normal open and close required torque is determined by the valve diameter size, work pressure and other factors, but because of assembly process valve manufacturers machining accuracy, distinction, with the specifications of the valve so that different manufacturers to produce the required torque is also different, even the same specifications valve torque is the same valve manufacturers are also different, cause can not be normal open and close the valve actuator torque choose too small will election type, so the electric actuator must to choose a reasonable torque range.
The correct choice of valve electric device based on:
Operating torque: torque operation is to select the main parameters of electric valve actuators, electric actuator output torque valve operation should be the maximum torque of 1.2 to 1.5 times.
Operation thrust: electric valve actuators of the host structure has two kinds: one is not configured thrust plate, the direct output torque; the other is the thrust plate configuration, the output torque is converted to the output thrust through the thrust plate of the stem nut.
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