Boiler feed water pump shafts are subjected to severe thrust loads and cyclic bending moments. Half-value width and residual stress measurements by X-ray diffraction methods, which are sensitive to fatigue damage, are employed for the fatigue life assessments of pump shafts. In order to establish a damage detection system, a portable, light-weight X-ray diffraction apparatus with a rotating receiving slit and X-ray detector and a small diameter X-ray tube has been developed. Consequently, the residual stress can be measured within 20 minutes which is about half the time required using a conventional apparatus. The X-ray apparatus has been installed in a system with a specially designed mechanical scanner for a pump shaft, and as a result, the fatigue damage can be automatically measured on the pump shaft surface. The system has been applied to more than 150 actual pump shafts in a factory during in-service inspections.
