Open AccessFailure analysis and revamping methods for loading threaded joints of raiseboring machine
Author(s) -
Guoye Jing,
Fuwen Hu,
Yun Chen
Publication year - 2020
Publication title -
iop conference series. earth and environmental science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.179
H-Index - 26
eISSN - 1755-1307
pISSN - 1755-1315
DOI - 10.1088/1755-1315/546/5/052064
Subject(s) - drill , borehole , mechanical engineering , engineering , preload , process (computing) , upgrade , shaft mining , fracture (geology) , structural engineering , forensic engineering , mining engineering , computer science , geotechnical engineering , medicine , hemodynamics , operating system
The process of raise boring (or back reaming) has been successfully employed for vertical mine development. The technology has successfully evolved from early small borehole diameter less than 2m to large diameter greater than 8m without incident. However, in our developed raise boring machines, the threaded joints connecting reamers and drill rods suffered several fracture accidents during reaming in different geological and geotechnical conditions. Under this background, it is undoubtedly of great engineering value to explore the failure mechanisms and put forward systematic quality control and risk control measures. The fractured threaded joints were visually examined on-site, and then examined in the laboratory using fractographic and metallographic examination, mechanical testing and chemical composition analysis. Firstly, the end faces of threaded joints could not to be installed to fit the end faces of spindles due to over-specified tolerances or insufficient preload. Secondly, it was found that the manganese (Mn) contents in material samples are higher than the national standards values. Thirdly, the heat treatment of water-quenching of workpieces perhaps caused a certain degree of residual stresses. Clearly this systematic inspection suggested we should take overall improvements to eliminate the potential failure mechanisms. After check and measurement of product and process performance, the cause-and-effect relationships undoubtedly were complex and multifaceted. Therefore, the component was redesigned using revamping methods including material compositions upgrade, fitting tolerances control, optimization of heat treatment process. Moreover, a systems approach and the institution of quality management system including increasing the preload, adding anti-dropping device and executing a Plan-Do-Check-Act cycle were implemented. Through this investigation and recommendations, the device has been in operation for more than two years without any problems.