Modern Industrial Requirements for the Use of Control Valves

Advanced modern industry is characterized by production automation. Examining the historical development and progress of automation systems, we can see that changes in technological tools have played an extremely important role. While a wide array of advanced control methods has continually emerged, the fundamental control principles have remained unchanged; by contrast, improvements in technological tools have been advancing at a rapid pace. The development and application of intelligent instrumentation further enhance the promising future of industrial automation. A typical automated control system comprises three main components: sensing, control, and actuation. In recent years, the influence of digital technology and microprocessor technology on sensing and control instruments has been unmistakable; meanwhile, the actuator segment—particularly the control valve, which is a key product—has also made substantial progress. Traditional control valves have generally met the needs of many industrial systems; however, with the large-scale expansion of modern industry,

How can we produce more and better advanced products? How can we raise product quality standards? How can we operate more efficiently and safely? And how can we make full use of resources, conserve energy, and protect the ecological environment? In response, people have increasingly higher requirements for control valves, which can be summarized as follows: greater stability in quality, greater reliability in operation, and enhanced safety in handling. In process control, control valves are in direct contact with the fluid; should a failure occur, the consequences could be disastrous.

In the petroleum industry, from oilfields to refineries, all production units are subject to large-scale centralized monitoring and control. Most operating conditions involve high temperature and low pressure or high temperature and high pressure, with process media consisting of various flammable and explosive oils and oil products; therefore, the reliability and fire safety of control valves are given top priority. In the chemical industry, the diversity of processes and the variability of operating conditions pose unique challenges in the control and actuation of the four major thermodynamic variables—temperature, pressure, flow rate, and liquid level—requiring control valves that can meet these specific application requirements.

In the power industry, thermal power plants must control their boilers, and maintaining proper water level in the boiler control system is of paramount importance, particularly in preventing inadvertent opening or closing of control valves. To ensure the performance and reliability of these control valves, the following requirements must be met:

1. Ensuring the Quality of Control Valves: The selection of control valves shall be based on rigorous calculations; the valve type, nominal size, and all performance parameters must meet the specified requirements; the materials used for all valve components must be carefully selected to ensure adequate strength and stiffness, and the valves must pass pressure-withstand tests, air-tightness tests, and other relevant tests in accordance with applicable standards. The manufacturer’s production technology and testing methods must comply with the relevant standards and be certified by the competent authority. It is strictly prohibited for small manufacturers lacking the necessary production conditions to engage in the manufacture of control valves.

2. Ensuring Reliable Operability This encompasses not only the manufacturing quality of the control valve itself, but also the training and professional development of operating personnel. To prevent misoperation, operators must strictly adhere to the precautions specified on the nameplate. According to China’s new standard for pneumatic control valves (GB/T 4213-92), the nameplate of a pneumatic actuator shall at a minimum indicate the manufacturer’s name, product model, rated flow coefficient, design tag number, product serial number, and date of manufacture. The valve body shall be cast or stamped with an arrow indicating the direction of media flow, as well as the DN designation and the PN rating. Critical valves must be equipped with adequate accessories, such as positioners and limit switches. Sufficient installation and operating space must be provided, along with adequate lighting and rigorously enforced operating procedures.