Underground » Mining Technology and Production
This project examined the potential of using fibre optic sensing technology for enhancing the monitoring and maintenance of longwall shearer operations, concentrating on the Bretby Cable Handling system. Recent developments in fibre optic technology have increased its accessibility and applicability, allowing measurements of various mechanical characteristics by exploiting properties of the optic fibre. These include parameters such as distributed axial strain and acoustic vibrations along the extended fibre lengths.
Laboratory tests were conducted using a sample high-voltage power cable with embedded optic fibres, and Bretby links from a mine site, to emulate the Bretby channel configuration and simulate longwall shearer conditions. The measurements recorded highlights the increased strain in the vicinity of Bretby bends, which can be indicative of emerging faults/wear in the Bretby cable. Some limitations were encountered, particularly when measuring across a 2km length, the narrower measurable frequency/wavelength sweep range led to lower signal-to-noise ratios. These experiments indicated that the strains experienced by the power cable is higher than initially anticipated and out of range for the commercially available Optical Frequency Domain Reflectometry (OFDR) interrogator.
Recommendations were also provided, highlighting the need to optimise measurement techniques and address limitations in the '2km' mode to enhance the reliability of strain profile data in cable monitoring systems. Furthermore, it is essential to use an interrogator with a wavelength sweep range of at least 5.25nm, or larger for applications with higher strains, for more accurate measurements.
The feasibility of an underground field trial was also assessed; but not undertaken as it faced significant challenges due to concerns regarding Explosion Risk Zones (ERZ) and the intrinsic safety issues associated with the interrogator used. The interrogator's limitations, such as its 2km range and restricted wavelength sweep range, necessitates custom-built interrogators.
This project explored the application of fibre optic sensing technology for improving longwall shearer operations' monitoring and maintenance. It identified limitations and provided recommendations for future efforts, while also evaluating the feasibility of an underground field trial.