Infrared Monitoring Techniques for Real-Time Monitoring of Rotary Ball Mills

This paper describes a method of analyzing an operating grinding mill through thermo-graphic imaging. Using highly sensitive imaging devices in conjunction with a rapid data collection program, relative amounts of energy introduced into the grinding elements or lost in the form of heat through the surface of the equipment can be determined. Thermo-graphic measurements performed on operating ball mills mirror increasing or decreasing grinding associated with linear samples taken from the interior of a crash stopped mill. This measurement method has been used to locate areas on operating mills where liners are subject to high wear due to an increased degree of metal-to-metal contact inferred by higher temperature readings than surrounding areas on the shell. The path of the grinding media against mill headliners is indicated by higher temperatures giving a true picture of how far grinding media is distributed along the circumferential path on the shell of a ball mill. The flow path of material along the length of a ball mill shell can also be determined. Where material is flowing faster through the mill, or along the mill shell, metal-to-metal contact increases. In one case, the flow rate increase was due to worn discharge grates, giving a warning as these wearing parts reached the end of their useful lifetime.