Problems and Challenges in Current Applications of Control Valves
Jun 27, 2024
A control valve is a device used to regulate the flow, pressure, temperature or level of a fluid, such as liquid, gas and steam. Control valves play a key role in industrial automation, ensuring the stability and efficiency of the production process through precise flow and pressure control. They are widely used in industrial fields, including chemical, petroleum, natural gas, pharmaceutical, food processing, and other industries. The function of a control valve is to adjust the amount of fluid passing through the pipeline by changing its opening to achieve the required process control. A control valve usually consists of a valve body, a valve, a valve seat, an actuator, and a supporting control system. The valve is a key component for controlling the flow of the medium, and its position is controlled by the actuator. The actuator can be manual (operated by humans) or automatic (driven by electric, pneumatic, and hydraulic). The control system adjusts the position of the actuator as needed to control the flow or pressure of the fluid.
Control valves face the following problems:
Problem 1:
There are many types of control valves with different specifications. The applications of control valves have characteristics of different process temperatures, front and rear pressure differences, valve resistance ratios, flow coefficients, and corrosion, requiring different valves to adapt to different working conditions. Control valves are all customized, resulting in non-universal models, long supply cycles, significant differences in the external dimensions, inability to provide accurate dimensions in the early stage, and different installation spaces. Because they are custom-made, each valve has its own maintenance characteristics, leading to problems such as complex daily maintenance and inconvenient management.
Problem 2:
The stability of the control valve is not uniform. Because the control valve is partially intercepted, the partial fluid morphology is special, even causing valve vibration. After the control valve is put into use for a period of time, the characteristic curve will change significantly. Even if the temperature, pressure, pressure difference, and other working conditions are exactly the same, there will be great differences due to different installation and use conditions, often resulting in increased leakage, increased noise, and changes in the characteristic curve, making it very difficult to maintain the initial performance for a long time. The components inside the control valve are flushed by the medium in the system for a long time, changing the original mechanical properties and the characteristic curve of the valve.
Problem 3:
With the expansion of industrial scale, there are more and more large-sized control valves. Large-sized control valves often require greater execution force, so their execution structure is larger, resulting in increased weight, which brings inconvenience to installation, maintenance, transportation, and inventory. Usually, the weight of a control valve is several times or even hundreds of times that of a general instrument. For example, a control valve of DN250 can weigh about 500 kg. Mechanical equipment is required for installation, maintenance, transportation, and inventory.
Problem 4:
The control loop control characteristics deteriorate during the control process of the control valve. The inherent flow characteristics of the control valve refer to the valve core flow path of the valve itself. Under a constant pressure drop, the relationship between the fixed stroke of the valve and the flow coefficient through the valve is determined at the factory. The installed flow characteristics are the relationship between the actual stroke and flow under the system operating conditions where the pressure drop is not constant, and each specific installation system will present a unique characteristic of the fluid at the valve. Therefore, it is easy for the inherent flow characteristics of the valve to not match the characteristics of the controlled engineering parameters, resulting in a deterioration in the control loop quality.
Problem 5:
The noise of the control valve has become one of the important sources of noise pollution in current industrial devices. Reducing the noise of control valves has become an important research topic to meet the requirements of occupational health and environmental protection.
Problem 6:
Control valves have high energy consumption, and the fluid in the system will inevitably lose energy when it flows through the control valve. As the use of the control valve increases, the leakage will continue to increase, with internal leakage occurring similar to the valve not being completely closed. This leakage causes the pressure before the valve to drop, resulting in pressure loss. Pneumatic actuators are commonly used in industrial sites and must always maintain a certain pressure to operate, increasing the energy consumption of some instrument gas, and the cost of producing products, as well as wasting energy.
In response to these problems faced by control valves, the following strategies and measures can be taken to deal with them:
Solution to problem 1:
The issue of different control valves with various specifications can be addressed by standardizing product design and manufacturing processes, reducing product varieties, and improving product versatility and interchangeability. Developing adjustable general products can adapt to different working conditions and reduce the demand for customized products. Formulating unified product standards and specifications will simplify product selection and procurement processes.
Solution to problem 2:
Inconsistent stability of control valves can be managed by regularly maintaining and overhauling the control valve to maintain their initial performance. Strengthening quality control will ensure product quality and stability. Introduce advanced materials and manufacturing technologies will improve the durability and stability of control valves.
Solution to problem 3:
The issue of large-size control valves can be addressed by developing lightweight materials and structural designs to reduce their weight. Developing convenient installation and maintenance tools can improve operational efficiency and safety. Optimize transportation and inventory management can reduce the inconvenience caused by weight issues.
Solution to problem 4:
The deterioration of control loop characteristics can be managed by carrying out systematic installation and commissioning of control valves to ensure that they match engineering parameters. Using advanced control technology and algorithms can improve the accuracy and stability of control loops. Improving monitor and adjustment of control valves during use can promptly detect and correct problems in control loops.
Solution to problem 5:
Noise and energy consumption of control valves can be solved by optimizing the structure and materials to reduce noise generation and energy loss. Introducing noise damping technology and energy-saving control strategies can reduce the noise and energy consumption. Strengthening monitoring and evaluation of noise and energy consumption, and continuously improving and optimizing the design and operation of control valves, will help address these issues. Through the implementation of the above measures, various problems faced by control valves can be effectively addressed, improving their performance and reliability in the field of industrial control, and reducing operating costs and environmental impacts.
Control valves face the following problems:
Problem 1:
There are many types of control valves with different specifications. The applications of control valves have characteristics of different process temperatures, front and rear pressure differences, valve resistance ratios, flow coefficients, and corrosion, requiring different valves to adapt to different working conditions. Control valves are all customized, resulting in non-universal models, long supply cycles, significant differences in the external dimensions, inability to provide accurate dimensions in the early stage, and different installation spaces. Because they are custom-made, each valve has its own maintenance characteristics, leading to problems such as complex daily maintenance and inconvenient management.
Problem 2:
The stability of the control valve is not uniform. Because the control valve is partially intercepted, the partial fluid morphology is special, even causing valve vibration. After the control valve is put into use for a period of time, the characteristic curve will change significantly. Even if the temperature, pressure, pressure difference, and other working conditions are exactly the same, there will be great differences due to different installation and use conditions, often resulting in increased leakage, increased noise, and changes in the characteristic curve, making it very difficult to maintain the initial performance for a long time. The components inside the control valve are flushed by the medium in the system for a long time, changing the original mechanical properties and the characteristic curve of the valve.
Problem 3:
With the expansion of industrial scale, there are more and more large-sized control valves. Large-sized control valves often require greater execution force, so their execution structure is larger, resulting in increased weight, which brings inconvenience to installation, maintenance, transportation, and inventory. Usually, the weight of a control valve is several times or even hundreds of times that of a general instrument. For example, a control valve of DN250 can weigh about 500 kg. Mechanical equipment is required for installation, maintenance, transportation, and inventory.
Problem 4:
The control loop control characteristics deteriorate during the control process of the control valve. The inherent flow characteristics of the control valve refer to the valve core flow path of the valve itself. Under a constant pressure drop, the relationship between the fixed stroke of the valve and the flow coefficient through the valve is determined at the factory. The installed flow characteristics are the relationship between the actual stroke and flow under the system operating conditions where the pressure drop is not constant, and each specific installation system will present a unique characteristic of the fluid at the valve. Therefore, it is easy for the inherent flow characteristics of the valve to not match the characteristics of the controlled engineering parameters, resulting in a deterioration in the control loop quality.
Problem 5:
The noise of the control valve has become one of the important sources of noise pollution in current industrial devices. Reducing the noise of control valves has become an important research topic to meet the requirements of occupational health and environmental protection.
Problem 6:
Control valves have high energy consumption, and the fluid in the system will inevitably lose energy when it flows through the control valve. As the use of the control valve increases, the leakage will continue to increase, with internal leakage occurring similar to the valve not being completely closed. This leakage causes the pressure before the valve to drop, resulting in pressure loss. Pneumatic actuators are commonly used in industrial sites and must always maintain a certain pressure to operate, increasing the energy consumption of some instrument gas, and the cost of producing products, as well as wasting energy.
In response to these problems faced by control valves, the following strategies and measures can be taken to deal with them:
Solution to problem 1:
The issue of different control valves with various specifications can be addressed by standardizing product design and manufacturing processes, reducing product varieties, and improving product versatility and interchangeability. Developing adjustable general products can adapt to different working conditions and reduce the demand for customized products. Formulating unified product standards and specifications will simplify product selection and procurement processes.
Solution to problem 2:
Inconsistent stability of control valves can be managed by regularly maintaining and overhauling the control valve to maintain their initial performance. Strengthening quality control will ensure product quality and stability. Introduce advanced materials and manufacturing technologies will improve the durability and stability of control valves.
Solution to problem 3:
The issue of large-size control valves can be addressed by developing lightweight materials and structural designs to reduce their weight. Developing convenient installation and maintenance tools can improve operational efficiency and safety. Optimize transportation and inventory management can reduce the inconvenience caused by weight issues.
Solution to problem 4:
The deterioration of control loop characteristics can be managed by carrying out systematic installation and commissioning of control valves to ensure that they match engineering parameters. Using advanced control technology and algorithms can improve the accuracy and stability of control loops. Improving monitor and adjustment of control valves during use can promptly detect and correct problems in control loops.
Solution to problem 5:
Noise and energy consumption of control valves can be solved by optimizing the structure and materials to reduce noise generation and energy loss. Introducing noise damping technology and energy-saving control strategies can reduce the noise and energy consumption. Strengthening monitoring and evaluation of noise and energy consumption, and continuously improving and optimizing the design and operation of control valves, will help address these issues. Through the implementation of the above measures, various problems faced by control valves can be effectively addressed, improving their performance and reliability in the field of industrial control, and reducing operating costs and environmental impacts.
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