The Influence of Method and Environment in Torquing Screws Used in Bucket Wheel to Stacker-Reclaimer Machine

摘要

Mining machines are of heavy-duty and robust type, and at the same time, they are keys to mining performance and operation. It is well known that mining environment is dirty and dusty as a whole, and this scenario contributes detrimentally for machines and equipment maintenance. This article reveals quantitatively the effect of the environment and the method in tightening screws to clamp the wheel buckets of a Stacker Reclaimer Machine at an Iron Ore Mining. For this study, a statistical tool called Minitab was utilized. The data were collected in the field during an intervention in the machine and treated statistically afterward. The elongations of the screws were measured by ultrasound which revealed that, when only torques are used to tighten the screws, referenced on the theoretical torque (N m) value, the aimed elongation (elastic strain) of screws might not be reached, with the worst case being it may be widely spread; the values obtained by ultrasound revealed such differences. After knowing such discrepancy, the screws were tightened properly to insure that the bucket wheel was correctly clamped. This statistical study quantified the spread values of torque versus elongation condition (bell curves). The ultrasound measurement credited the method utilized.