- Author
- Hjelmstad, K. E. | Pomroy, W. H.
- Title
- Novel Fire Warning System for Underground Mines.
- Coporate
- Bureau of Mines, Minneapolis, MN
- Journal
- Mining Engineering, Vol. 42, No. 1, 107-112, January 1990
- Keywords
- coal mines | mine fires | warning systems | fire protection
- Identifiers
- mines and mining; underground mining; electromagnetic signaling
- Abstract
- In the event of fire underground, it is essential that all miners be warned as quickly as possible. With mine air rapidy depleted of oxygen and contaminated with smoke and toxic fire gases, any delay in the warning signal could have disastrous consequences. Unfortunately, present mine fire warning systems, such as stench, audible or visual alarms, telephones, and messengers, are often slow, unreliable, and limited in coverage. Recent research by the US Bureau of Mines has established the feasibility of ultralow frequency electromagnetic signaling for underground mine fire warning. In field testing completed thus far at five mines, signals from 630 Hz to 2000 Hz were transmitted through rock up to distances of 1645 m (5400 ft) to a pencil-sized ferrite-core receiving antenna and intrinsically safe receiver circuit. Theoretical analysis indicates a capability to transmit effectively for distances in excess of the maximum depths of most American mines, which is about 900 to 1000 m (2950 to 3280 ft). The prototype system uses off-the-shelf components and state-of-the-art technology to ensure high reliability and low cost. This technology would enable simultaneous and instantaneous warning of all underground personnel, thereby increasing the likelihood of successfully evacuating a mine during a disaster. This report discusses the theoretical basis for through-the-rock ultra flow frequency electromagnetic transmission, design of the prototype transmitter and receiver, and the results of in-mine tests of the prototype system.