Abstract
Mining machines' components, or the whole structure, are prone to frequent premature damages and fractures what is explained either by inadequate design and construction or by insufficient knowledge of the material's and welded joints' properties and oversights in manufacturing. Here is considered the bucket-wheel excavator, i.e. the fracture of the tooth of the girth gear, which enables the circular motion of the excavator's upper structure (which was in operation for 5000 hours). The gear was made of the cast steel GS 40 MnCrSi3 V. The reparatory hard-facing (HF) technology of the fractured tooth required specification of numerous operations including the preparation works. The reparation realized the two-fold savings, in time and money - the new girth gear costs over 500 000 € and its manufacturing lasts 6 to 9 months, while the safety and quality of the repaired tooth was guaranteed.
Highlights
The Bucket wheel excavators (BWE) are in exploitation subjected to stresses that appear in manufacturing of parts and mounting of equipment, as well as during their functioning and during the disrupted exploitation [1,2]
It was employed on excavation of the barren soil for 5.000 h when the fracture of the tooth of the girth gear, which enables the circular motion of the upper structure of the bucket-wheel excavator, occurred
Considering that the excavator is still in operation at the open pit mine “Kostolac” (Serbia), it could be concluded that the reparation was successful
Summary
The Bucket wheel excavators (BWE) are in exploitation subjected to stresses that appear in manufacturing of parts and mounting of equipment (residual stresses), as well as during their functioning (stationary and dynamic loadings) and during the disrupted exploitation (nonstationary dynamic loadings) [1,2]. It was employed on excavation of the barren soil for 5.000 h (a few weeks more than a year after the assembly) when the fracture of the tooth of the girth gear, which enables the circular motion of the upper structure of the bucket-wheel excavator, occurred. Precisely define a large number of details and carefully consider and execute all the operations in the methodology of manufacturing the new tooth This was an imperative in order to ensure the safety of the repaired girth gear exploitation, since the smallest oversight, underestimate or improper execution could cause serious problems in the operation of the BWE as a whole. This is the reason why the preparation procedure for the hard-facing technology is presented, as well
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