Cane-sugar making has been a principal industry in Oinawa for a long time, and recently the equipments and processes of the sugarmaking has been modernized by introducing high pressure boilers and steam turbines. So, the proper operation and maintenance of every mechanical unit in the factory have become important tasks from the viewpoint of engineers, because a single trouble of the mechanical unit will possibly cause a large damage in the operation of the mill plant. This paper deals with a systematic analysis of a mechanical accident of the mill turbines and reduction gears at one of the cane sugar mill plants in Okinawa. The work includes the investigation of the operative and maintenance conditions at every mechanical unit, visual identification of the damaged parts (mill turbine axis, teeth of the reduction gears, metal bearings and the couplings) and the composition analysis of the turbine axis material. Through a close examination of these minor analyses, the main factors which have caused the accident are pointed out as follows: 1) The fatigue phenomenon on the face of the damaged turbine axis 2) The eccentric revolution of the turbine axis due to the wear of the metal bearings arings 3) Axial forces between the flanges of the couplings while the eccentric running of the turbine axis 4) Scratched flaws on the thrust faces of the metal bearings 5) The large clearance between the metal bearing and the turbine axis.
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