【Haichuan’s Lessons from Other Places】Overcoming Critical Challenges: Ningxia Petrochemical’s Domestication of the Control System for Ammonia Tank Refrigerators

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“Under the control of the new operating system, the ammonia tank chiller operates more efficiently and stably, with its cooling capacity increased by 15%; this results in cost savings of at least 800,000 yuan per year. ”On November 15, at the site of the trial operation of the new system for the ammonia tank refrigerators in Ningxia’s petrochemical and fertilizer facility, project leader Lei Yueqiang pointed to the display screen of the upgraded system and told reporters. After months of intensive efforts, the company has recently completed the localization transformation of the control system for the last York screw compressor – namely the ammonia tank chiller – thereby breaking the foreign technological monopoly and laying a solid foundation for the stable, efficient, and continuous operation of the refining facilities. 　　Ningxia Petrochemical has a total of 5 screw compressors, which are responsible for cooling the circulating water in the polypropylene plant and cooling ammonia gas in the fertilizer plant; they serve as key equipment to ensure the smooth operation of petrochemical production. The original control systems for the 5 screw compressors were imported systems. Since the manufacturer kept the system programs and algorithms confidential, it was not possible to view the control logic online. As a result, when faults occurred in the equipment, it was difficult for technicians and operators to determine the cause; they had to rely on the manufacturer’s technical staff to come to the site for assistance, which increased the costs associated with repairs. Furthermore, as this control system is one of the company’s early products, it has frequently experienced crashes and black screens in recent years. The high costs and long turnaround times associated with equipment repair and maintenance have become significant obstacles to the efficient and stable operation of the device. 　　To completely resolve this critical bottleneck issue, Ningxia Petrochemical made a decisive decision to localize the control system of the York screw compressors. Taking advantage of the favorable opportunity provided by the comprehensive maintenance campaigns on its refining and fertilizer production facilities, the company carried out systematic planning and implemented the changes in phases, ultimately carrying out thorough renovations to the control systems of all 5 screw compressors. Through a series of rigorous steps such as technical evaluation, scheme design, personnel training, and testing, the company developed a new screw compressor control system, which was integrated into the Zhejiang Zhongkong ECS700 system and the Hollyland MACS system. 　　The renovation not only enabled a \"rewiring\" of the compressor but also achieved a \"superiority\" in terms of functionality. The new system boasts powerful data collection and logical processing capabilities. Technicians can view in real time the operation status of logical controls as well as historical data on process parameters. It also allows for real-time recording of the operations carried out by staff, enabling better analysis and optimization of equipment performance, thereby significantly improving operational efficiency and production stability. 　　During the renovation, to address the issue of spool drift in the original system caused by minor leaks in the cylinders and solenoid valves during operation, the Mechanical Equipment Department of Ningxia Petrochemical, in collaboration with technicians from the Electrical and Instrumentation Center, added a self-retention function for the spool position. This feature enables the seals to maintain a stable load capacity even in the presence of minor leaks. Additionally, the startup logic of the lubricating oil pump was optimized, and new interlock functions for displaying parameters such as temperature, inlet pressure, and exhaust pressure were introduced. These functions provide a basis for quickly identifying the cause of faults, thereby further enhancing the safety of the equipment. 　　During the renovation process, Ningxia Petrochemical adopted a construction method of \"pre-fabrication in the factory + on-site assembly\", which effectively shortened the on-site construction period and reduced construction costs. The successful implementation of this project not only resolved the critical challenges encountered in the production and operation processes of Ningxia Petrochemical, but also yielded valuable experience in replacing complex imported equipment control systems with domestic alternatives. It provided a replicable and scalable \"Ningxia Petrochemical model\" for the renovation and upgrading of similar equipment in the industry, serving as a vivid example of China’s efforts to localize petroleum equipment and enhance the security and resilience of its industrial supply chains.