There are many types of electric actuators. Different types and functions of electric actuators can be called electric valves when they are matched with valves. However, in the planning and selection process, only the parameters of the valve are ignored or the electric actuator is not clearly defined. Related requirements, this will not only make the electric valve not perform the best function, but also bring unnecessary troubles in the process of equipment, commissioning and operation, and even give severe results to the production.
This article will clarify the key considerations for the selection of electric actuators, and briefly introduce the related functions of current intelligent electric actuators. It will be the mainstream product required for the development of industrial automation control today and in the future.
(I) The key considerations in the selection of electric actuators:
(1) recognize the output torque of electric actuators based on the torque required by the valve
The torque required for valve opening and closing determines the output torque selected by the electric actuator. Generally, it is proposed by the operator or selected by the valve manufacturer. As the actuator manufacturer is only responsible for the output torque of the actuator, the valve is required for normal opening and closing. The torque is determined by the valve diameter, operating pressure and other factors. However, due to the differences in valve manufacturers' processing accuracy and equipment technology, the torque required by the same valve produced by different manufacturers is also different. Even the same valve produced by the same valve manufacturer. Standard valve torque is also different. When the torque of the actuator is too small, the valve cannot be opened and closed normally. Therefore, the electric actuator must choose a reasonable torque plan.
(2) The electrical parameters are recognized according to the selected electric actuator.
Because the electrical parameters of different actuator manufacturers are different, it is generally necessary to recognize their electrical parameters when planning and selecting, mainly including motor power, rated current, secondary control loop voltage, etc., which are often ignored in this regard. Mismatches with electric actuator parameters constitute faults such as air-open trips, fuse blows, and thermal overload relay protection trips.
(3) Choose the enclosure protection level and explosion-proof level according to the application
(4) Select electric actuator according to valve type
There are many types of valves, and the operating principles are not the same. Generally, the opening and closing control is completed by rolling the valve plate angle, lifting valve plate and other methods. When supporting the electric actuator, the electric actuator should be selected according to the valve type.
1.Angle stroke electric actuator (rotation angle <360 degrees)
The roll of the output shaft of the electric actuator is less than one week, that is, less than 360 degrees, and generally 90 degrees completes the opening and closing process control of the valve. This type of electric actuator is divided into direct connection type and base crank type according to the different interface methods of the equipment.
a) Direct connection: refers to the method of directly connecting the output shaft of the electric actuator to the valve stem.
b) Base crank: refers to the method of connecting the output shaft to the valve stem through the crank.
This type of electric actuator is suitable for butterfly valves, ball valves, plug valves, etc.
2.Multi-turn electric actuator (rotation angle> 360 degrees)
The roll of the output shaft of the electric actuator is more than one week, that is, more than 360 degrees. It usually takes multiple turns to complete the opening and closing process control of the valve.
This type of electric actuator is suitable for gate valves, globe valves, etc.
3.Straight stroke (linear motion)
The movement of the output shaft of the electric actuator is a linear motion type, not a rolling method.
This type of electric actuator is suitable for single seat regulating valve, double seat regulating valve, etc.
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