Mining industry operations must be monitored continuously to avoid operational hazards and downtimes, including the mine conditions and heavy machinery used for processing and exploring metals, materials, and minerals extracted from Earth. This article discusses different sensor systems and their role in mining applications.
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Importance of Sensors in the Mining Industry
Using sensors in the mining processes can protect critical assets and ensure safe operation. Sensors are already used extensively in mining operations, including remote operation and automation applications.
Major Sensor Applications in Mining Operations
Imaging, three-dimensional (3D) mapping and ranging
Image and mapping sensors, such as visual, infrared (IR), and depth sensors, are typically used in the mining industry for remote and local surveillance of operations, equipment control and monitoring, and vehicle automation.
They are also used in large-scale topography and mapping, cave evolution tracking, stockpile monitoring, particle measurement, and rock face measurement. Specifically, IR cameras are used in vehicles and other mining equipment for collision avoidance, vision in poor lighting conditions, and equipment condition monitoring.
Depth sensors based on IR time of flight and fixed structured light technology and stereoscopic sensors can provide mm-accurate values, while sensors based on programmable structured light provide µm-accurate values.
Laser equipment is used in remote mapping for rock face profiling in inaccessible locations. 3D mapping is often based on the combination of position/orientation and optical sensors. In specific cases, proximity and depth sensors are also used along with optical and position sensors for 3D mapping.
Equipment and machine condition monitoring
Condition monitoring of machines and equipment is crucial for improving their operational lifetime and reducing downtime through optimized preventative maintenance scheduling.
Different embedded sensors, such as temperature, vibration, pressure, and strain sensors, are often used to identify operational parameters such as engine speed, speed of movement, location, blowby pressure, engine oil pressure, fuel consumption rate, exhaust temperatures, and boost pressure.
The information is used along with additional information, such as the number of operational hours per day and service meter readings, to estimate the overall health of the machines.
Tire pressure and temperature monitoring
Tire temperature and pressure monitoring systems (TPMS) can improve safety, tire life, fuel efficiency, and mine productivity.
In TPMS, the pressure and temperature sensors inserted in the tire can directly communicate with the mine vehicle operator in real-time using several wireless visualization and connectivity options.
Hazardous gas monitoring
Hazardous gas monitoring systems reduce the risks in mines created by toxic and flammable gases, such as methane, and depleted oxygen levels under harsh mine conditions with significant pressure fluctuations, rapid humidity variations, and extreme temperature changes.
Pellistor gas sensors are currently utilized on machinery and mine walls to detect hazardous gases. Other mining gas sensors include catalytic, electrochemical, and infrared gas sensors.
Mine fire monitoring
Temperature, smell, and humidity sensors can detect impending mine fires. Temperature sensors, such as thermocouples, resistance thermometers, and thermistors, can detect the changes in underground mine temperature to indicate fires.
Smell sensors based on the piezoelectric effect can indicate fires as mine fires result in the generation of organic gases, carbon dioxide, and carbon monoxide, significantly changing the typical odor in mines.
Smoke detectors, such as ionization-type smoke detectors, optical beam-type smoke detectors, and photoelectric-type smoke detectors, can also detect heat or fire in mines more efficiently and reliably than other sensors.
Humidity sensors, including capacitive and resistive humidity sensors, can detect impending mine fires by identifying the changes in the humidity level.
Tracking and localization
Different sensor technologies are currently utilized for tracking, communication, and detecting the absolute and relative positions of humans/miners, equipment, and vehicles.
Sensor systems, such as terrestrial positioning systems based on radio frequency (RF), satellite systems based on global positioning system (GPS), tagging technology, beacon sensors, and dead reckoning systems/inertial sensor-based position tracking are typically used for localization and tracking applications, such as personnel location, mining site security, asset tracking and management, remote equipment operation, and driverless vehicle control.
Sensors based on GPS, Global Navigation Satellite System (GLONASS), Galileo, and BeiDou are used for real-time global positioning. GLONASS and GPS can provide an accuracy of five meters, while the Galileo and BeiDou-based sensors provide cm-accurate positioning. Cm-scale absolute positioning sensors are more suitable for mining operations.
RF positioning sensors are often used for indoor locations. Recently, a real-time ultra-wideband tracking system with dual communication, high precision, and greater scalability has been proposed for better navigation in mining sites.
Location beacon sensors are used extensively for cave tracking in mining monitoring. Beacons mark the ore locations to predict waste ingress into the ore during mining activities.
This real-time cave motion monitoring technology can also enable cave motion optimization. Moreover, beacon sensors can be utilized for local positioning by providing checkpoints or proximity information.
Proximity sensors are used for tracking and positioning in combination with other positioning technologies or as stand-alone systems. In mining operations, these short-range sensors are used explicitly for orientation and position control of automated equipment, such as driverless vehicles, to avoid collisions and improve personnel safety.
Several sensing methods, such as gravity gradiometry sensors and time-lapse seismic monitoring, are used to discover new mineral deposits. Remote detection methods that are deployable using aircraft are typically preferred during exploration due to the need to investigate large geographic expanses.
Gravity gradiometry sensors can determine the underground density profile of Earth to indicate the presence of mineral deposits. The electrostatic gravity gradiometer (EGG) was recently introduced to discover mineral deposits with significantly higher accuracy.
Seismometers are designed to measure the large amplitude, low-frequency motion of the Earth’s crust using an inertial mass suspended by a wide-frequency response spring structure.
These sensors are often used to estimate the underground composition during exploration stages. Time-lapse seismic monitoring implies continuous seismic vibration monitoring for a dynamic understanding of the site behavior.
The Future of Sensors for Monitoring Underground Mining Stability
To summarize, sensors increasingly play a critical role in several mining applications. In the future, closer cooperation between mining, analytics, networking, and sensing industries can facilitate more efficient and sustainable mining operations.
Read more: How Sensors Can Prevent Mining Accidents
References and Further Reading
Kiziroglou, M. E., Boyle, D. E., Yeatman, E. M., Cilliers, J. J. (2016). Opportunities for Sensing Systems in Mining. IEEE Transactions on Industrial Informatics. https://www.researchgate.net/publication/311697237_Opportunities_for_Sensing_Systems_in_Mining
Ehsan, E. (2017) Sensor Systems in Mining Industry. Nanotechnology Letters. https://www.pulsus.com/scholarly-articles/sensor-systems-in-mining-industry.pdf
Mishra, P. K., Kumar, S., Mandal, P.K. (2013). APPLICATION OF SENSORS FOR DETECTION OF UNDERGROUND COAL MINE FIRE: A REVIEW. https://www.researchgate.net/publication/337243316
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