Eddy-current Nondestructive Testing Equipment for Cracks in Land-based Gas Turbine

Abstract

It is quite important to nondestructively comprehend the depths of surface-breaking cracks for the life assessment and judgmental standards for timing to recoat blades in land-based gas turbines. Eddy current testing (ECT) is very attractive because it offers both very high detectablity and high scanning speeds. However it is not straightforward to apply a conventional ECT probe to blades having complex geometry. Flexible ECT probe arrays have been developed to overcome the major limitations of existing systems. The use of an array of sensors allows cracks of all lengths to be detected and will ultimately allow real time data imaging to provide rapid inspection and easy interpretation. In this study based on eddy current techniques, crack detection equipment was developed and applied to 1100℃-class gas turbine blades for field use. By using this equipment, ECT data can be quickly taken at leading edges, and concave and convex sides of the blade mounted in a rotor after a turbine casing is removed.