What is Electric Valve Opening Control?
In modern industrial production, the application of electric valves is ubiquitous. From petroleum and chemical industries to food, pharmaceuticals, water treatment, and energy sectors, electric valves play an indispensable role. Their efficient and precise control capability provides strong assurance for the smooth operation of various complex process flows. This article will explore in depth the multiple methods of achieving opening control in electric valves, as well as the advantages and challenges of these technologies in practical applications, helping readers fully understand the operating principles and value of this important industrial equipment.
The core component of an electric valve is the electric actuator, which acts as the “brain” of the valve. It can receive external control signals and convert them into mechanical motion, thereby realizing the adjustment of the valve opening. When the control signal reaches the motor in the actuator, the motor begins to rotate. The rotation of the motor, through a series of transmission devices such as reduction gearboxes and worm gears, transmits power to the valve stem. The movement of the valve stem may be linear or rotary, depending on the type of valve. For example, butterfly valves and globe valves change the valve opening by rotating the valve stem to drive the valve core.
The forms of control signals are diverse, with common ones being 4–20mA current signals and 0–10V voltage signals. These analog signals can precisely control the motor’s speed and rotation angle according to their magnitude and proportional relationship with valve opening. In chemical production processes where high precision in flow regulation is required, adjusting the magnitude of the 4–20mA signal can precisely control the opening of the electric control valve, thereby realizing accurate control of material flow. In addition, discrete signals can also be used to control the forward and reverse rotation of the motor, thereby achieving full opening or full closing of the valve.
To ensure that the valve opening can accurately reach the set value and remain stable, a feedback mechanism is indispensable. In electric actuators, potentiometers are often installed as feedback elements. The resistance value of the potentiometer changes with the valve opening. By measuring the resistance value, the control unit can obtain real-time valve opening information. The control unit then compares the feedback opening value with the set value and adjusts the motor’s movement according to the deviation so that the valve opening reaches and maintains the required position.
In addition to potentiometers, Hall sensors and photoelectric sensors are also commonly used feedback elements. A Hall sensor is based on the Hall effect. When current passes through and is placed in a magnetic field, the Hall element generates a Hall voltage, which is related to the magnetic field strength and the current. By installing the Hall sensor in an appropriate position in the electric actuator, it can sense the magnetic field changes caused by changes in valve opening, thereby generating corresponding electrical signals to feed back to the control unit and realizing accurate measurement and control of valve opening.
Photoelectric sensors, on the other hand, detect the position or motion of objects by emitting and receiving light. In electric valves, the transmitting and receiving ends of a photoelectric sensor can be installed on fixed and movable parts of the valve, respectively. When the valve opening changes, it blocks or alters the light path, causing the intensity of light received to change. This change is converted into an electrical signal fed back to the control unit, thereby realizing monitoring and control of valve opening.
We will introduce in detail several common methods of electric valve opening control, including proportional control, PID control, fuzzy control, and neural network control. These control methods not only hold theoretical significance but also demonstrate excellent performance in practical applications.
Proportional control is a method of control based on the proportional relationship between the input signal and the actual valve opening. When the input signal changes, the electric actuator drives the valve to change its opening accordingly according to the set proportional coefficient. This control method responds quickly and can achieve relatively smooth adjustment of opening, suitable for occasions requiring high regulation accuracy.
PID control, namely Proportional (P), Integral (I), and Derivative (D) control, is a more advanced control method. By adjusting these three parameters, the PID controller can automatically adjust the control signal based on the deviation between the actual opening and the set opening, eliminating steady-state error and improving system stability and response speed. PID control is widely applied in various industrial automation systems for electric valve opening control, particularly excelling in situations requiring high precision and fast response.
Fuzzy control is a control method based on fuzzy logic, which transforms human experience and judgment rules into a fuzzy control rule base. The control unit, according to the input fuzzified signals, uses a fuzzy inference engine to carry out reasoning and derive control decisions, thereby realizing control of valve opening. Fuzzy control has the advantages of strong robustness and good adaptability, making it suitable for nonlinear and time-varying complex systems. In industrial processes difficult to describe with precise mathematical models, fuzzy control can play an important role.
Neural network control is a method that uses artificial neural networks to learn and train with large amounts of data. Through training, the neural network can establish the mapping relationship between input signals and valve opening. In actual operation, based on real-time input data, the neural network model can control the valve opening. Neural network control has strong adaptability and generalization ability, suitable for highly nonlinear and strongly uncertain systems. With the continuous development of artificial intelligence technology, the application prospects of neural network control in electric valve opening control are broad.
Electric valves can be classified into various types according to the type of opening feedback: without opening feedback, with only two states (open or closed), and with continuous opening feedback. Among them, valves with continuous opening feedback are the ideal pursuit of manufacturers and operators, as they provide the most precise control and richest information. However, the cost of valves with continuous opening feedback is relatively high, which requires many users to weigh cost and performance when making a choice.
For valves without continuous opening feedback, some technical means can be used to compensate, enabling them to achieve continuous opening feedback. For example, a step PID controller can be used. This controller calculates the increase or decrease of valve position based on the error signal between the set value and the measured value, then outputs pulse signals to drive the motor forward or backward to achieve valve control. When the valve needs to remain in a certain position, the controller does not require any output signals. This control method improves the control accuracy of valves without continuous opening feedback to some extent, enabling them to meet the requirements of more industrial applications.
Electric valves have many advantages that make them the first choice in many industrial situations. First, electric valves are easy to assemble, and installation and maintenance costs are relatively low. Second, they have low failure rates, high reliability, and can operate stably for long periods in harsh working environments. In addition, electric valves meet industry needs for automation, seamlessly integrating with various control systems to achieve remote monitoring and automated operation.
Compared with traditional pneumatic valves, electric valves do not require complex piping, solenoid valves, compressors, and other equipment. This not only simplifies system design but also reduces operating costs. In situations with space and resource limitations, the advantages of electric valves become even more evident.
As an important type of industrial equipment, electric valves play an indispensable role in modern industrial production. Through various advanced control technologies and feedback mechanisms, electric valves can achieve precise opening adjustment, meeting the requirements of complex process flows. Whether in traditional industrial fields such as chemicals and petroleum, or in emerging fields such as food, pharmaceuticals, and water treatment, electric valves, with their efficiency, precision, and reliability, provide strong assurance for the smooth operation of industrial production.
