Fibre optic sensors for coal mine hazard detection

A number of health and safety hazards present in underground coal mines, which include methane gas explosion, coal combustion, rock roof collapse, and flooding etc. Methane gas and coal combustion have been two major hazards, which resulted in most of the heavy casualties and economic losses. Conventional catalytic methane gas sensors suffer from poor accuracy and cumbersome maintenance, which is the bottleneck of methane hazard prevention. Coal mine combustion monitoring has been relying on gas tubing bundles system, which suffers from long time delay and poor reliability. Semiconductor laser diode methane gas sensors have been developed which has low power consumption, 0-100% full detection range and high accuracy, and no need of recalibration. Fibre optic Raman distributed sensors have been deployed in coal mine goaf and successfully detected combustion hazard in early phase. The FOS-based mine hazard detection system offers unique advantages of intrinsic safety, multi-location and multi-parameter monitoring. The application of FOS on monitoring of methane, coal combustion, micro-seismic and equipment condition are described, future trend of research in this area is also discussed.