An Unusual Method Ror Replacing a Rotor Spider in a Water-Wheel Generator

Ultrasonic tests made following the discovery of cracks in the hub of a caststeel rotor spider of a 15,000-kva waterwheel generator indicated the advisability of replacing the spider with one of modern fabricated steel design. Economic considerations favored making the replacement without disturbing the field poles and laminated rim. A special jacking rig was devised with which the spider was pressed out of the rim in approximately 90 working hours. Removal of the old spider and installation of the new spider was accomplished in 34 shifts and required 2,570 man-hours. Estimated savings of 48.5% in time and 43.6% in labor were made by performing the work in this manner rather than by the conventional method of removing field poles, unstacking the laminated rim from the old spider, restacking the laminations on the new spider, and reinstalling the field poles.