Volume 20, Issue 4 (July 1992)
Magnetic Particle Testing of Turbine Blades Mounted on the Turbine Rotor Shaft
Turbines constitute some of the most critical elements in such things as aircraft engines and power generating plants where breakdowns can be catastrophic. Preventive maintenance is therefore vital in such situations. Non-Destructive Evaluation (NDE) plays a significant role in such maintenance programmes. Turbine blade failure can occur without warning and with disastrous results. Such failures are, for the most part, caused by cracks or less frequently, by inclusions. Such defects are readily detected by NDE techniques such as magnetic particle inspection (MPI) if they are on or near the surface and accessible, which is the case in turbine blades.
This paper outlines the general technique of MPI of turbine blades mounted on the turbine rotor shaft with specific reference to the placement of the magectizing coils. Of the two practical techniques, the method of placing a preformed coil over a number of blades in one row is preferred to the method of wrapping the coil around the rotor shaft across an entire row of blades.