What are Pneumatic Pressure Control Valves?

In modern industrial production, the control of fluid pressure is a task of vital importance, as it concerns the safety, stability, and efficiency of the production process. Pneumatic pressure control valves, as highly efficient and precise fluid pressure control devices, play an indispensable role in numerous industrial fields due to their outstanding performance and reliable operation. This article will provide a detailed introduction to the composition, working principle, installation points, and maintenance inspection highlights of pneumatic pressure control valves, with the aim of helping relevant practitioners to better understand and use this equipment, ensuring its optimal performance in practical applications.

Pneumatic pressure control valves mainly consist of a pneumatic diaphragm control valve, a smart PID controller, a pressure transmitter, and accessories such as a 3-core shielded cable. Among these, the pneumatic diaphragm control valve is the core component of the entire system. It features a cage-type sleeve guidance, a double-seal structure, and is equipped with a multi-spring pneumatic diaphragm actuator. This structural design endows the actuator with advantages such as low height, light weight, and easy installation, effectively reducing the costs of equipment installation and maintenance.

The valve core of the control valve adopts a cage-type sleeve valve core. Its working principle is to convert the air source pressure into the linear displacement of the valve core, thereby automatically controlling the opening of the control valve and achieving continuous regulation of the fluid pressure in the pipeline. Through this method, pneumatic pressure control valves can automatically regulate and control the pressure of media such as water, steam, gas, and liquid with high precision (up to ±0.2%) using PID control. Their regulation performance and control accuracy far exceed those of conventional self-acting pressure control valves.

Moreover, pneumatic pressure control valves also employ a self-feedback system. The pressure transmitter collects real-time changes in the pressure of the regulated medium and transmits these change signals to the smart PID controller. The controller, based on the preset control strategy, converts the signals into standard control signals of 0 - 10V or DC4 - 20mA, which in turn control the valve opening. This self-feedback mechanism enables the control valve to quickly respond to pressure changes, maintain stable system pressure, and ensure the smooth progress of industrial production processes.

To ensure the normal operation and long-term stable working of pneumatic pressure control valves, correct installation is of utmost importance. The following points should be observed during the installation process.

The installation position of the control valve should be at a certain height from the ground to facilitate routine maintenance and repair work by operators. Sufficient space should be left above and below the valve to allow for disassembly and repair. For control valves equipped with pneumatic valve positioners and handwheels, the convenience of operation, observation, and adjustment must be ensured. Under normal circumstances, the control valve should be installed on a horizontal pipeline, with the valve body's vertical direction aligned with the pipeline. In most cases, it is also necessary to provide support beneath the valve to ensure the stability and reliability of the equipment. However, in some special situations, if it is necessary to install the control valve horizontally on a vertical pipeline, it should also be supported (except for small-diameter control valves). During installation, it is important to avoid imposing additional stress on the control valve, which could affect its normal operation.

The working environment temperature for the control valve should be between -30℃ and +60℃, with a relative humidity not exceeding 95%. Exceeding this temperature and humidity range may lead to a decline in equipment performance or even malfunction. Therefore, the working environment should be assessed before installation to ensure it meets the operational requirements of the equipment.

There should be straight pipe sections before and after the control valve, with a length of no less than 10 times the diameter of the pipeline (10D), to avoid short straight pipe sections that could affect the flow characteristics. If the diameter of the control valve is different from that of the process pipeline, a reducing pipe should be used for connection. For small-diameter control valves, threaded connections can be employed. During installation, it is crucial to ensure that the fluid direction arrow on the valve body is consistent with the actual flow direction of the fluid, so that the control valve can correctly control the fluid pressure. Additionally, a bypass pipeline must be set up to facilitate switching or manual operation, as well as maintenance of the control valve without shutting down the system.

Before installation, all foreign matters in the pipeline, such as dirt and welding slag, should be thoroughly removed. These foreign matters may clog the control valve, affect its normal operation, and even cause equipment damage. Therefore, cleaning the pipeline before installation is an essential step to ensure the long-term stable operation of the control valve.

Maintenance and inspection of pneumatic pressure control valves are key to ensuring their long-term stable operation. Regular maintenance and inspection can promptly identify potential issues, prevent equipment failures, and extend the service life of the equipment. During maintenance and inspection, the following aspects should be given particular attention:

Due to the infiltration of the medium during operation, the internal surface of the threads used to fix the valve seat is prone to corrosion, which may lead to the loosening of the valve seat. The sealing performance of the valve seat is crucial for the normal operation of the control valve. If the valve seat becomes loose, it may cause fluid leakage and affect the regulation accuracy. Therefore, during maintenance and inspection, it is necessary to carefully check whether the fixing threads of the valve seat are intact and whether there are any signs of corrosion. If severe corrosion is found, prompt measures should be taken to repair or replace it to ensure the sealing performance of the valve seat.

In working conditions with high pressure differences and corrosive media, the inner wall of the valve body and the diaphragm of the diaphragm valve are often subjected to the impact and corrosion of the medium. The pressure and corrosion resistance of these components directly relate to the safety and reliability of the control valve. During maintenance and inspection, it is important to focus on checking the pressure and corrosion resistance of the valve body inner wall and diaphragm, observing whether there are any issues such as corrosion, wear, or deformation. If problems are detected, they should be repaired or replaced in a timely manner to prevent fluid leakage or other safety accidents caused by component damage.

The valve core is one of the movable parts of the control valve and is susceptible to corrosion and wear due to the erosion of the fluid. Particularly in situations with high pressure differences, the wear of the valve core may be exacerbated by cavitation. Cavitation refers to the phenomenon where the local pressure of the fluid decreases to below the saturation vapor pressure of the liquid during high-speed flow, causing the liquid to vaporize and form bubbles. When these bubbles burst in high-pressure areas, they generate strong shock waves that can severely damage the valve core. Therefore, during maintenance and inspection, it is necessary to carefully examine all parts of the valve core for signs of corrosion, wear, or cavitation. If the valve core is severely damaged, it should be replaced immediately to ensure the normal operation of the control valve.

Packing is an important component in the control valve used to seal the gap between the valve stem and the valve body. Over long-term use, packing may gradually age due to factors such as medium erosion and temperature changes. If the packing ages or is damaged, it may lead to leakage at the valve stem, affecting the sealing performance the of control valve. Therefore, during inspection and maintenance, it is necessary to check whether the packing is dry. For packing using polytetrafluoroethylene (PTFE) filler, it is also important to check whether it has aged and whether the mating surfaces are damaged. If problems are found, the packing should be replaced promptly to ensure the sealing performance of the control valve.

Pneumatic pressure control valves have several advantages, including compact structure, light weight, sensitive action, low pressure drop loss, large valve capacity, precise flow characteristics, and convenient maintenance. These advantages enable pneumatic pressure control valves to perform well in various industrial settings and meet the needs of different users.

During operation, pneumatic pressure control valves can maintain stable pressure control, avoiding production accidents caused by pressure fluctuations. This is crucial for production processes with high requirements for pressure stability. For example, in chemical production, many reaction processes require extremely precise pressure control. Pneumatic pressure control valves can ensure that reactions take place under stable pressure conditions, thereby improving product quality and production efficiency.

Pneumatic pressure control valves have a large allowable pressure difference, meaning they can operate normally over a wide range of pressures. In high-pressure difference working conditions, such as oil and natural gas pipelines and high-pressure steam systems, pneumatic pressure control valves can effectively control fluid pressure and ensure the safe operation of the system. In contrast, some traditional pressure control valves may experience unstable operation and decreased sealing performance under high pressure differences, while pneumatic pressure control valves can effectively overcome these difficulties.

In industrial production, equipment noise is often a concern, especially in places with high requirements for working environment noise. Pneumatic pressure control valves are designed to reduce noise and produce relatively low noise levels during operation. This not only helps improve the working environment and reduce hearing damage to operators but also lowers the risk of production accidents caused by noise interference. For example, in pharmaceutical and food processing plants with high environmental requirements, the use of pneumatic pressure control valves can effectively reduce noise pollution and improve the quality of the production environment.

Pneumatic pressure control valves are particularly suitable for working conditions with low allowable leakage and large pressure differences between the valve inlet and outlet. In situations with extremely high sealing requirements, such as chemical raw material storage tanks and hazardous chemical pipelines, pneumatic pressure control valves can ensure fluid sealing control and prevent leakage accidents. At the same time, in high-pressure difference settings like high-pressure boilers and high-pressure reactors, pneumatic pressure control valves can operate stably and meet the production process requirements for pressure control. In addition, pneumatic pressure control valves are widely used in water treatment systems, air conditioning and refrigeration systems, food and beverage processing systems, and many other fields, providing reliable fluid pressure control solutions for various industrial production processes.

As an advanced fluid pressure control device, the pneumatic pressure control valve is widely used in modern industrial production due to its high control precision, excellent regulation performance, reliable working stability, and wide range of applications. Through rational design, correct installation, and regular maintenance and inspection, pneumatic pressure control valves can operate stably over the long term, providing strong support for the safety, stability, and efficiency of industrial production processes. For relevant practitioners, a deep understanding of the composition, working principle, installation points, and maintenance and inspection highlights of pneumatic pressure control valves not only helps to improve the operating efficiency of the equipment but also effectively reduces equipment failure rates and extends service life, thereby creating greater economic benefits for enterprises.