Development of an Ultrasonic Testing Robot for Retaining Rings in Turbine Generators

To eliminate the need for rotor disassembly and post-inspection cleaning required by conventional liquid couplants, an automated robotic system equipped with a newly developed dry couplant was developed. The robot enables ultrasonic inspection of the entire circumference and outer surface of the retaining ring through optimized circumferential and axial drive mechanisms, pressing control, and adaptable holding fixtures. Performance evaluations were conducted using actual generator rotors and full-scale mock-up test pieces. The robot demonstrated stable and repeatable traversal on retaining rings of various sizes. The dry couplant maintained sufficient ultrasonic transmission and defect detection capability after more than 50,000 loading cycles, with no observable degradation or operational failures.

These results confirm that the developed system possesses the fundamental functionality and durability required for practical, fully automated ultrasonic inspection without rotor disassembly. The system significantly improves inspection efficiency, reliability, and cleanliness compared with conventional methods, and development is currently progressing toward productization and field application.