Valve electric device is to realize the valve program control, automatic control and remote control of the indispensable driving equipment, its movement can be driven by the stroke, torque or axial thrust of the size to be controlled.
The operating characteristics and utilization of the valve actuator depend on the type of valve, the operating specification of the device and the position of the valve on the pipeline or equipment.
Select the electric actuator according to the type of valve 1.
Angular Stroke Electric Actuator (corner "360 degrees") applies to butterfly valves, ball valves, plug valves and so on. Motor actuator output shaft rotation less than one week, that is less than 360 degrees, usually 90 degrees on the valve to achieve the opening and closing process control.
This type of electric actuator according to the installation of different interface mode is divided into direct-connected, base crank-type two.
A direct connection: refers to the electric actuator output shaft and valve stem directly attached to the form of installation.
B) The base crank type: Refers to the output shaft through the crank and the valve stem connection form. 2. Multi-rotary Electric actuator (corner 360 degrees) for gate valves, Globe valves and so on.
Electric actuator Output shaft rotation is more than one week, that is greater than 360 degrees, generally require more than a circle to achieve the valve control of the headstock process. 3. Straight stroke (linear motion) is suitable for single seat control valve, two-seater control valve, etc.
The motion of the output shaft of the electric actuator is a linear motion, not a rotational form.
Second, according to the production process control requirements to determine the electric actuator control mode 1. Switch-type (open loop control) switch-type electric actuator generally realize the valve on or off control, the valve is either in the open position, or in the full position, such valves do not need to accurately control the flow of media. It is particularly worth mentioning that the switch-type electric actuator can be divided into the structure and the integrated structure because of the different structure forms.
Selection of this must be explained, or often occur in the on-site installation and control system conflicts and other mismatches are like. A the split structure (commonly referred to as ordinary): The control unit is separated from the electric actuator, the electric actuator can not realize the control of the valve alone, the control unit must be applied to control, the general external use of the controller or control cabinet form supporting.
The disadvantage of this structure is not easy to install the system as a whole, increase wiring and installation costs, and prone to failure, when the fault occurs when not easy to diagnose and repair, the cost is not ideal. B the integrated structure (usually called the integral type): the control unit and the electric actuator are packaged into one, without the external control unit can be practical in-situ operation, remote only output related control information can be operated on. The advantage of this structure is to facilitate the overall installation of the system, reduce wiring and installation costs, easy to diagnose and troubleshooting.
But the traditional integrated structure product also has many imperfect place, therefore has produced the intelligent electric actuator. 2.
Adjustable type (closed loop control) electric actuator not only has the function of switch-type integrated structure, but also can control the valve accurately and adjust the flow of media.
A control signal type (current, voltage) the control signal of electric actuator usually has current signal (4~20ma, 0~10ma) or voltage signal (0~5v, 1~5v), the type and parameter of control signal should be clear when selecting. B the type of work (electric open, electric switch type electric actuator working mode is generally open type (take the control of 4~20ma for example, the electric open type refers to the 4MA signal corresponding to the valve, 20MA corresponding to the valve open), and another type of electrical clearance (with 4-20ma control as an example,
Electric open type means that the 4MA signal corresponds to the valve open, 20MA corresponds to the valve clearance.
(C) Loss of signal protection loss signal protection refers to the line and other failures caused by the loss of control signals, electric actuators will control the valve to set the value of the protection, the common protection value of full open, fully closed, maintain in situ three.