Mining Contract: Method for Improving Ventilation & Gas Monitoring with an Advanced Fiber Optic Based Mine-Wide Monitoring System
OMSHR has previously developed atmospheric monitoring systems in order to minimize the risk of underground mine fires and explosions. However, the need to improve the accuracy, quantity, and timeliness of methane and temperature measurements taken throughout the mine, the hours devoted to sensor calibration and system maintenance, and the utility of these systems to be used in the most active areas of a mine, remote workings, and bleeder entries are gap areas that remain. Also, the system has to be designed to be functional following a large-scale catastrophic event.
Contract Status & Impact
This contract is complete. To receive a copy of the final report, send a request to OMSHR@cdc.gov.
The objective of this project was to develop and test a prototype mine-wide monitoring system, based on laser energy distributed through a fiber optic network that will monitor in near real time and record the atmospheric concentration of methane and the ambient temperature. This information will provide an indication of potential or actual explosion or fire conditions in underground coal mines.
RSL Fiber Systems, LLC, was contracted to develop an advanced fiber-optic-based mine-wide methane and temperature monitoring system. This system does not require any underground electrical power and therefore can remain operational in the event of an underground power outage. It provides a wide dynamic methane gas measurement range with sensitivity as low as 150 parts per million and the ability to measure up to 100% methane in the environment. Additionally, it has been shown to be immune to water and any cross-interfering gases likely to be present. It can potentially be expanded to monitor other gases, smoke particles, diesel particulate matter, and possibly coal dusts.
The contractor designed and assembled a prototype fiber optic-based system that can reliably produce an alert signal when, at any methane sensor location, methane concentrations equal 1%; and reliably produce an alarm signal when, at any sensor location, methane concentrations equal 1.5%. The sensors are self-calibrating and require no periodic maintenance and could potentially be used in all active and inactive areas of the mine. The prototype system also includes a distributed temperature system capable of detecting ambient temperature and rate of temperature rise, and provides alert and alarm signals when values exceed limits established via control software. The temperature system achieves spatial resolution of less than one meter and thermal resolution of less than one degree Celcius at less than 15-second measurement intervals.
The potential impact of the system to the coal mining industry is significant. The ability to sense methane remotely, without the need for maintenance or calibration, enables direct sensing in mined-out areas, providing valuable information to the mine operators on a real-time basis. The methane sensing system also facilitates the potential to utilize ventilation-on-demand (VOD) to improve efficiency and effectiveness of the mine ventilation system. The ability to collect and subsequently analyze the data for trends as well as correlation to other events, such as barometric pressure changes, provides another level of control to the mine. Finally, the ability of the temperature sensing system to provide early detection of machinery failures or fires before they become catastrophic provides a cost-savings as well as a safety benefit.
The system was designed and built in a manner that meets Mine Safety and Health Administration (MSHA) approval requirements for intrinsic safety under 30 CFR Part 18.68. The prototype system, four methane sensors, and 1,000 feet of temperature sensing were installed in an active underground coal mine for extended system testing and evaluation.