Strength problems of the travelling mechanisms of the open pit machines

The extremely heavy duty conditions of the Surface Mining Machines (SMM) provide fertile ground for the occurrence of the various types of failures in their travelling mechanisms and belonging substructures. Although failures of the SMM travelling mechanisms occur infrequently, they may lead to very serious or even disastrous consequences. Even in cases when consequences are not catastrophic they cause direct costs, as well as indirect costs due to the downtime that substantially diminishes the effects of SMM exploitation. Furthermore, replacement of damaged parts is executed on site, often in hard working conditions that essentially prolong the downtime of the complete surface mining system. This paper discusses the causes of the failures in the vital parts of the crawler travel gear of the bucket wheel excavators and spreaders: chain links, track wheels, two-wheel bogies and undercarriage. Based on the results of the analytical–numerical–experimental analyses, it was concluded that: (a) chain links' failures are caused by 'manufacturing-in' defects; (b) track wheels' failures are caused by 'design-in' and ' manufacturing-in' defects; (c) failures of the twowheel bogies and undercarriage are caused by 'design-in' defects. Besides that, the redesigned structures of the two-wheel bogies and undercarriage are presented. The validity of the presented reconstruction designs are unquestionably confirmed by their failure less exploitation after the reconstruction. Finally, the obtained results are important because the same problems could arise in the crawler travelling mechanisms of wide class of earthmoving and material handling machines