Fracture of 13'X42' cement mill and its repair, and strain gauge testing of the drive

A cement mill sustained a 42' shear fracture due to a combination of flexural shear and torsional shear. The large fracture of the shell was accompanied by a 5' circumferential crack in the meehanite casting. The shell fracture was successfully repaired using preheat and mechanical bracing. Full thermal stress relief in situ was achieved. The structure was shimmed to achieve good alignment for the drive. The casting was repaired using mechanical fasteners. Strain gauge tests were performed to evaluate the magnitude of torsional shear stress during start-up and steady state running conditions. The strain gauges monitored the clutch engagement time, with the peak stresses measured in the drive shaft. The downtime was 10 weeks.<>