Mechanical and Electrical Limits in Control Valve Actuators
On this page
Control valve electric actuators play a crucial role in automated control systems, primarily used to regulate and control the opening and closing states of control valves, thereby adjusting the flow of media in pipelines. To ensure the normal operation of control valve electric actuators and prevent potential damage, the limit system is particularly important. The limit system of control valve electric actuators mainly includes two types: mechanical limits and electrical limits. The following is a detailed introduction to these two types of limit systems and their adjustment methods.
Mechanical Limit
A mechanical limit is a system that controls the range of motion of control valve electric actuators through physical components. Its main purpose is to prevent the control valve from exceeding the set opening and closing angles during operation, thereby protecting the motor and control valve from potential mechanical damage.
1. Working Principle
The mechanical limit prevents the control valve electric actuator from exceeding the preset operating range through physical components, thereby protecting the motor and control valve from damage due to excessive rotation.
Structure: The mechanical limit device is usually installed on the motor's drive shaft. As the motor rotates within a 0-90 degree range, the limit block rotates with the motor, ensuring that the control valve's opening and closing is controlled within the set range.
Adjustment: The opening range of the mechanical limit is usually adjustable by about ±10 degrees. Users can precisely set the control valve's opening and closing position by adjusting the bolts, ensuring that the control valve does not exceed the set angle.
Function: The main function of the mechanical limit is to prevent motor damage due to operational errors, thereby ensuring the normal operation and extending the service life of the control valve electric actuator.
2. Adjustment Method
Initial Setup: The mechanical limit screw of the electric actuator is adjusted and secured at the factory. Users generally do not need to adjust it under normal circumstances.
Adjustment Steps: Confirm the control valve position limited by the limit screw. The screw on the right is the close limit screw, and the one on the left is the open limit screw.
Screw in the limit screw until it contacts the end face of the sector worm wheel, then back it out by 0.5-1 turns to set the travel limit or the safety protection of the over-torquing. Tighten the loosening nut on the outer end of the limit screw to complete the adjustment.
Testing: After the adjustment is completed, perform a test of the control valve's opening and closing to ensure that the mechanical limit setting meets the requirements.
Electrical Limit
The electrical limit system is a technology that controls the on and off state of the control valve electric actuator through electrical signals. It relies on electrical components and controllers, precisely controlling the control valve's position by turning the power on and off, ensuring that the control valve operates within the set range.
Working Principle
The electrical limit system achieves the on and off control of the control valve through electrical signals, providing higher accuracy. The mechanism is as follows.
Electrical Components
Micro Switch: The electrical limit system typically includes one or more micro switches. These switches are installed on the transmission shaft of the electric actuator, used in conjunction with cam or other moving parts.
Cam: The transmission shaft of the electric actuator is usually equipped with a cam. As the motor rotates, the cam squeezes or releases the micro switch, thereby controlling the power on and off.
Control Mechanism
Power Switch: When the motor rotates to the set switch position, the cam squeezes the micro switch, cutting off or connecting the power. This mechanism achieves the on and off control of the control valve through electrical signals.
Feedback Signal: The electrical limit system can provide real-time feedback on the control valve's position status, allowing the control system to adjust operations according to actual conditions.
Function
Precise Control: Controlling the control valve's on and off state through electrical signals can achieve higher accuracy and avoid mechanical errors.
Automated Operation: Electrical limits can be integrated with automatic control systems to achieve automated operation and remote monitoring.
Coordination of Mechanical and Electrical Limits
Mechanical and electrical limit systems complement each other in control valve electric actuators to achieve precise control of the control valve. The advantages of their combined use are as follows.
Precise Control: Mechanical limits provide physical protection, while electrical limits achieve more precise control through electrical signals. The combination of the two can effectively improve the accuracy of control valve control.
Prevent Faults: The coordinated operation of the two can effectively prevent motor work faults, ensuring that the control valve operates within the predetermined range.
Precautions: In actual use, the settings and adjustments of mechanical and electrical limits must be consistent. If the actions of the two are not consistent, it may lead to motor faults or inaccurate control valve control.
The mechanical and electrical limit systems of control valve electric actuators provide a solid guarantee for the precise control of control valves through their unique functions and mutual cooperation. Proper adjustment and coordination of these two types of limit devices are key to improving system stability and reliability. The electric control valve limit switch box plays an important role in automatic control systems, providing support for control valve status detection and system feedback. Understanding the working principles and adjustment methods of these limit systems helps to ensure the normal operation of control valve electric actuators and improve the accuracy of pipeline medium flow control.
