Evolution of the Ultrasonic Inspection over the Past Decades on the Example of Heavy Rotor Forgings

Several decades ago the first ultrasonic inspections were introduced to assure component integrity. Those were, in the beginning, manual, straight beam, contact probe inspections with simple, non-descript reporting requirements. The development of ultrasonic inspection capabilities, the change in design engineer requirements, improvements of fracture mechanics calculations, experience with operation, experience with the inspection technology, and probability of detection (PoD) drove the changes that have resulted in the current day inspections. This process is described on the example of heavy rotor forgings for land-based power generation turbines and generators and shows how sizing technologies were implemented, detection limits lowered, angle and pitch/catch (dual crystal) probes introduced, and automated systems required for the inspection. Due to all these changes, model based sizing techniques and modern ultrasonic techniques, like phased array, are being introduced globally. This paper describes the evolution of the ultrasonic inspection over the last decades and presents an outlook for tomorrow.