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Enhancing underground mine safety with 'through the rock' communications

Mine Site Technologies recently completed the latest tests of its wireless, two-way, digital underground mining communication system in a West Virginia coal mine.

Author: John Chadwick
Posted: Monday , 10 Mar 2008

LONDON -

Mining disasters in the U.S., China and Australia focused considerable attention on the need for highly reliable communications.

Two-way wireless communications between underground and surface will greatly enhance rescue efforts in the event of a mine accident. An important breakthrough is emerging in this area.

As Denis Kent of Mine Site Technologies (MST) points out, "dependence on underground infrastructure is acceptable in the day-to-day operation of a mine, but can lead to some shortcomings in certain emergency situations. Digital systems will contribute positively to safety, they will not be able to meet all contingencies in an emergency so should not be installed in isolation, but in combination with other complementary technologies to ensure higher levels of redundancy and back up in an emergency."

MST and its distributor for eastern US, CSE Corp, have completed the latest demonstrations of the Two-Way PED System in West Virginia. Undertaken at Patriot Coal's Federal No.2 coal mine, the demonstrations (two-way messaging between surface and underground) were witnessed by Peabody Energy personnel, as well as representatives from Consol Energy, MSHA and NIOSH.) Federal No.2 was an excellent location as it provided two areas within the one mine that demonstrations could be undertaken with different depths of cover; one at 230 m and the other at 335 m.

In both instances two-way messaging was achieved with signals propagating directly through-the-earth from the miner underground to the surface installation. The received signal strength was reduced at the 335 m deep section of the mine as expected, but was still sufficient for two-way messaging back and forth. Additionally the test site was a 'worst case' location as it also had an electrical sub-station earthing mat in the area, which added further attenuation to the signals. Having achieved two-way messaging to a depth of 480 m at West Cliff coal mine in Australia it was expected to operate successfully, but ensuring the signal penetration in the geological setting of eastern U.S. coal measures made the demonstrations very worthwhile.

The development plan is to have production versions of the Two-Way PED Refuge Bay Stations available to the industry by the end of 2008. The Refuge Bay Station will allow through-the-earth signaling from strategic places underground such has Refuge Bays, SCSR caches, etc, so people can communicate with the surface and advise of their movements, number and condition of the people at that location.

Designed to withstand fire and explosion, the Refuge Bay Stations will remain operational and available to personnel underground whatever happens to the mines other hard wired and fixed communication systems.

The intent of the Federal MINERS Act was to encourage the development of a truly wireless system. That is, a system where "wireless" means a communication method with virtually no hard wiring underground; and not just a system that depends on extensive underground infrastructure with just the last link in that extensive chain being a wireless radio link.

The only way to eliminate extensive cabling and infrastructure underground is to have the communication system transmit directly through rock strata. MST and CSE are confident that the Refuge Bay Station will meet this requirement of being truly wireless.

John Chadwick is Editor/Proprietor of International Mining magazine - www.im-mining.com