Environmental impact on the magnetic field distribution of a magnetic proximity detection system in an underground coal mine

Abstract

A magnetic proximity detection system mounted on an underground mobile mining machine detects whether a worker is hazardously close to the machine. The system generates magnetic fields covering the extended spaces around the machine. A magnetic detector worn by the worker measures the magnetic field flux density and determines the distance from it to the machine. The system is frequently in close proximity to coal as the machine moves, causing the magnetic field flux, in part, to enter massive in situ coal. This has the potential to have an adverse effect on the accuracy of the system and on the safety of the worker if the coal were to significantly alter the magnetic flux density distribution. Two experiments were conducted to study the impact of in situ coal on these magnetic fields. Measurements in one mine show that coal mass has no significant impact on the magnetic field flux distribution.

Keywords:

• equivalent circuit
• magnetic analysis
• magnetic field measurement
• magnetic flux density
• near-field radiation patterns

Acknowledgments

The authors gratefully acknowledge the contributions of Mr Joseph Ducarme, Dr Christopher Jobes, Mr Timothy Lutz, Mr Miguel Reyes, Mr Adam Smith, Mr Bruce Whisner, and Mr Jeffrey Yonkey for their work on the experiment set-up and data collections.