A leading brand in the power generation industry was looking to modernize the transformer cooling system at a pumped-storage power plant, including the design, manufacturing, delivery and assembly of new TEMA AEW-type shell-and-tube heat exchangers. These units were intended for cooling power transformers using river water as the cooling medium. The project included adaptation to existing piping connections and structural interfaces, as well as ensuring high reliability for continuous operation.
The existing heat exchangers suffered from recurring damage at the critical tube-to-tubesheet joints. These failures led to operational interruptions, necessitating the replacement of the exchangers and creating an urgent need for a more reliable solution. The scope covered corrosion-resistant coolers for four transformers — replacing 16 units in total — and included a fluid-mixing prevention system and leak detection.
To meet the high-quality requirements and eliminate prior operational issues, the following advanced technologies were implemented:
• Use of TEMA AEW-type heat exchangers, fully manufactured from corrosion-resistant 316L stainless steel, suitable for operation with river water and transformer oil.
• Expansion of the tubes into the tubesheet to ensure a tight seal.
• Laser welding with a mirror system providing precise and reliable tube-to-tubesheet joints, minimizing the risk of leakage and eliminating stress concentration.
• Lantern ring leakage detection system, placed between the water and oil sections, enabling early detection of leaks before water can enter the oil system.
• Execution by a highly experienced team of engineers and certified welders, ensuring top-quality construction and compliance with industry standards.
The modernization of the heat exchanger system at the pumped-storage power plant delivered a reliable, durable and fully customized solution that meets the demanding operating environment of transformer cooling with river water and supports long-term operational safety.
Key outcomes:
An electric power company was looking for a reliable and high-quality heat exchanger manufacturer for a power plant modernization project. The scope was to replace four transformer oil coolers with units that would work efficiently without failure.
The modernization of the transformer cooling system at the pumped-storage power plant began when the existing heat exchangers began to experience frequent failures. The most critical issue involved recurring leaks at the tube-to-tubesheet joints, which posed a serious threat of river water entering the transformer oil system. Engineers concluded that a complete replacement with modern TEMA AEW heat exchangers made entirely of corrosion-resistant 316L stainless steel was necessary. The new design included the delivery and installation of 16 units, four for each of the four transformer blocks. Each exchanger was fully adapted to the existing piping layout and supporting structures, ensuring seamless integration within the power plant. A key technological upgrade was the use of laser welding with a mirror system, providing extremely precise and durable tube-to-tubesheet joints.
This advanced welding process eliminated stress concentrations and prevented the micro-cracks responsible for earlier failures. Additionally, the implementation of a floating tubesheet design helped avoid fractures and leakages caused by insufficiently compensated thermal expansion resulting from high-temperature differences between the oil and water sides. To further improve safety, a lantern-ring leakage detection chamber was installed between the water and oil sections, enabling immediate detection of even minimal leaks. This system ensured that intervention could occur before any water entered the oil circuit, protecting the integrity of the transformer.
The entire manufacturing and assembly process was carried out by the highly experienced AHE team from AIC S.A., ensuring compliance with demanding industry standards. After installing the new exchangers, all failures previously associated with tube-to-tubesheet joints were completely eliminated. The system has since operated safely using river water as the cooling medium, thanks to corrosion-resistant materials and precision engineering. The reliability of the transformer cooling process increased significantly, improving the overall stability of the power plant. Since the modernization, no downtime or financial losses have been recorded due to transformer cooling issues. This project demonstrates how advanced engineering solutions, high-quality materials, and modern fabrication technologies can deliver a durable and fully customized system for demanding power generation environments.
