2005: First Proximity System Approved MSHA for Underground Mining
Frederick Mining Controls, LLC was the first company to develop a proximity safety system that MSHA approved for use in underground coal mining. This system also was the first to be tested in a 30-day pilot program under the direct control of MSHA, conducted in the Jones Fork mine in eastern Kentucky. Important inventions were incorporated into this system. Refer to Patent # 7,420,471 for more details about the system design.
This first underground proximity system approved for coal mining has numerous features that make it suitable for coal mining and is formed around the use of low frequency magnetic fields. Functionally, it is a closed-loop or active system. A generator on a machine produces a magnetic field which is detected by a Personal Alarm Device (PAD) carried by a pedestrian. When the PAD detects the magnetic field, a UHF response is sent back to the generator. Thus, the pedestrian, the system, and the operator of the machine can each be warned of an unsafe condition, so that actions can be taken to stop the machine and warnings can be given to all.
Low frequency magnetic fields can be made to be very precise and stable so that safe zones or danger zones can be relied upon to remain in their designed or chosen locations. They do not reflect from metallic or other conducting surfaces to cause multi-path signals that lead to system failure. These fields also easily penetrate earth formations and most other materials so that detecting pedestrians is not blocked by most materials. Also, since the magnetic fields are produced in the shape of a solid ellipsoid, the fields go around objects that are between a magnetic field generator and a pedestrian.
These fundamental characteristics of a closed-loop, magnetically-based technology are also ideal for non-mining applications.