The current use and requirements of pneumatic control valves in industry

Advanced modern industry is marked by production automation. Looking at the development history and progress of automation systems, the change of technical tools plays an extremely important role. Various advanced control methods have emerged continuously, but the basic control laws have not changed, while the improvement of technical tools is changing rapidly. The development and use of intelligent instruments have opened up a promising future for industrial automation. A typical automatic control system mainly consists of three links: detection, control, and execution. In recent years, the impact of digital technology and microprocessor technology on detection instruments and control instruments has been evident, and the actuator link, especially the pneumatic control valve as the main product, has also made considerable progress. Traditional control valves basically meet the needs of many industrial systems, but with the large-scale development of modern industry, how to produce more and better advanced products, how to improve product quality standards, how to operate more effectively and safely, and how to fully utilize resources, save energy, and protect the ecological environment, people have raised higher requirements for control valves. These requirements can be summarized as follows: more stable quality, more reliable operation, and safer operation. In process control, control valves directly come into contact with fluids. If they fail, the consequences would be unimaginable.

    In the petroleum industry, various production devices are monitored and controlled on a large scale, from oil fields to refineries. Most operations are conducted under high temperature and low pressure or high temperature and high pressure conditions, with various flammable and explosive oils serving as the medium. Therefore, the reliability and fire resistance of regulating valves are prioritized. In the chemical industry, due to the diversity of processes and changes in process conditions, there are special requirements for regulating valves in the control and execution of the four major thermal variables: temperature, pressure, flow rate, and liquid level.

    In the electric power industry, thermal power plants must control their boilers. Maintaining normal water levels in the boiler regulation system is crucial to avoid misoperations of the regulating valves, which is of utmost importance. To ensure the performance and reliability of the regulating valves, the following requirements must be met:

    1. Ensure the quality of pneumatic control valves. The selection of control valves must undergo rigorous calculations; their type, caliber, and various performance indicators must meet the requirements. The materials of various parts of the control valves must be strictly selected, possessing sufficient strength and rigidity, and must pass pressure tests, air tightness tests, and other tests in accordance with national standards. The manufacturing technology and testing methods of the manufacturer must comply with standards and be signed and approved by the competent department. It is strictly prohibited for small factories without production conditions to engage in production.

    2. Ensuring reliable operability not only refers to the manufacturing quality of the pneumatic control valve itself, but also includes the training and improvement of the quality of operating personnel. To prevent misoperation, process personnel must pay attention to the precautions indicated on the nameplate. According to China's new standard for pneumatic control valves (GB/T4213-92), the nameplate of the pneumatic actuator should at least indicate the manufacturer's name, product model, rated flow coefficient, design tag number, product number, and manufacturing date. The valve body should be cast or stamped with arrows indicating the direction of medium flow, as well as DN values and PN letters and values. Important valves should have sufficient accessories, such as positioners and limit switches. There should be sufficient installation and operating space, adequate lighting, and strict operating procedures.