Redesign of a scanner for EC- and UT-measurements in the central bores of large rotors in power plants — With focus on an electromechanically actuated leg-unit for passing steps in bottle-bores without using pneumatic actuation

In this paper we present the redesign of a scanner for eddy-current (EC) and ultrasonic (UT) measurements in the central bores of large rotors in power plants. It focuses on an innovative leg-unit which allows for passing steps and thus is able to scan in almost all types of straight bores above 70mm. It is actuated purely electromechanically, using a serial-elastic power transmission with a spindle and foil-potentiometers for measuring force and position. In contrast to previous designs it does not need any additional pneumatic or hydraulic supplies. For this reason, the deployment is significantly simplified both in terms of installation time and logistics. After explaining the application and showing the limitations of previous designs, the main concepts and principles are described, concluding with a brief report on the successful test-runs and an outlook to future extensions.