Underground » Maintenance
This project is phase 2 of the distributed acoustic sensing project aimed at developing a technology for monitoring the condition of conveyor belts using fibre optics. Phase 1 (published as C24014), was a proof of concept phase which ended with a demonstration that an acoustic interrogator coupled to a fibre optic cable running the length of a conveyor belt is capable of detecting sounds with sufficient clarity to diagnose wear in the bearings of the idlers.
The objectives of this project were to take the proof of concept work from phase 1 through to a “minimum viable product”, in other words to create a first generation tool that maintenance engineers on a mine site would be able to use effectively.
The work required for phase 2 had a wide range of technical issues to be understood and overcome. A clear understanding of the way bearings wear and fail and the sequence of how the failures develop had to be understood. This led to the development of a library of acoustic spectral signatures, a wear development flow chart and a new vocabulary relating sounds to frequency patterns to bearing condition. Methods of attaching the fibre to the steel frame had to be experimented with and techniques developed. This led to an investigation of the acoustic transmission properties of the steelwork of a conveyor and the ways in which that affected the detection by the fibre. It was found that the spectral signatures captured from the fibre are swamped with noise which dominates any attempt to use acoustic energy as a diagnostic tool. As a result, a complex sequence of signal processing algorithms were strung together in order to extract from the noise, some normalised patterns that truly represented the library of wear and failure modes. Many dead ends were explored before the correct signal processing sequence was uncovered.
The phase one report is C24014 and is also available for download from the ACARP website.