Abstract: During maintenance, it was found that the output shaft of reducercracked and the inner hole of the output gear was worn. The analysis indicated that the fatigue resistance of the output shaft of reducer material was insufficient, which induced the cracking of the output shaft of reducer. The expeller operated under medium and low loads for a long time when producing dry rubber. Meanwhile, the design layout of the screw was unreasonable and the clearance between the screw and the barrels was small, which caused scraping and grinding of the screw and the barrels, thus triggering the abnormal noise and vibration. The fatigue cracking of the output shaft of reducerwas accelerated under the combined action of alternating loads, abnormal vibration and accumulation of lubricating oil elements. The clearance fit between the output shaft of reducer and the output gear intensified the micro motion between them due to the cracking of the output shaft of reducer,which eventually led to the wear of the inner hole of the output gear. In view of the fact that the wear of the output gear inner hole was within controllable limits, the treatment plan was adopted to repair the inner hole and the surface of the output gear. And the cracked output shaft of reducer needed to be replaced by a new one. The new domestically produced output shaft of reducer adopted 34CrNi3Mo with better mechanical performance and the heat treatment process was optimized. And then, it was paired with the repaired output gear inner hole. In addition, the layout of the screw has been optimized; the outer diameter of the screw has been appropriately reduced and the operating load of the unit has been increased in order to make the operation of the dewatering extruder safer and more stable.

Key words: dewatering extruder, output shaft of reducer, fatigue cracking, SBS, output gear repair, screwadjustment