Development of an In-situ Slew Bearing Scanner for Shovels

This report details the development steps for a new in-situ slew bearing scanner for shovels. The aim of the project was to:

• Develop an in-situ scanner that can examine the slew bearing rails on a shovel for spalling damage and hence provide mine sites with an assessment of the condition, rates of deterioration, remnant life and replacement strategy; and to
• Undertake a trial scan of a shovel slew bearing using the developed scanner as a proof of concept.

Ascribe Engineering routinely undertakes scanning of the slew bearings on draglines. Here, the slew bearings are composed of upper and lower rails and rollers that are held together by an inner and outer band. Because of the size and layout of dragline slew bearings, it is possible to remove a roller and install the scanner into that location. The machine can then be slewed with the scanner installed inside the roller path and the condition of the upper and lower rails is then established.

Unlike draglines, the slew bearings on shovels are significantly smaller and it is not possible to remove a roller without separating the machine. Consequently, in order to install a scanner into the roller path in a shovel, a new and miniaturised scanner was required to be designed that could be installed in the upper and lower gaps between adjacent rollers.

The methodology of the project was to:

• Inspect an existing shovel slew bearing to obtain various dimensional information;
• Design and build a miniaturised scanner;
• Undertake a trial install of the scanner and if successful; and
• Perform a trial scan of the upper and lower slew bearing rails.

Each of these project steps was successfully executed and the project culminated in a proof of concept scan undertaken on a spalled P&H XPC 4100 shovel slew bearing. The proof of concept scan was successful and demonstrated that the scanner was able to detect spalling of the upper and lower rails of the slew bearing. On the upper rail, it was found that spalling was present primarily at the LHS and RHS frontal areas on the revolving frame rail. These two locations most likely corresponded to the primary load path location from the boom foot connections which provided a stiffer support than the rest of the revolving frame. On the car body rail, spalling was fairly widespread but concentrated to the LHS and RHS of the car body. This most likely corresponded to the most worked orientation of the shovel (i.e. digging with the boom oriented at approximately right angles to the crawler tracks).

The spalled shovel slew bearing was subsequently dismantled and the spalling visually inspected. Very good comparison with the results from the scanner and the spalled regions observed on the rail surfaces was found and gives further confidence in the use of the scanner as a detection tool for early spalling and spalling progression through the lifecycle. Importantly, there were no false positives of spalling detected by the scanner or from the data processing strategy used. As the manual inspection process for establishing the condition of the slew bearing in a shovel is time consuming and not all areas of the slew bearing can be accessed, a major safety gain from this project has been achieved by removing personnel from being in the confined space between the upper and lower sections of the slew bearing for extended periods. Further, by providing a much more comprehensive and detailed condition assessment of the slew bearing, the overall risk to a machine from an unplanned failure of the slew bearing is reduced.