Design, Certification and Manufacture of an IS Geophone for Underground Coal Mining

Two geophone assemblies have been developed and accredited as intrinsically safe (Ex ia) under the IEC scheme. The first geophone is a single element uni-axial geophone and the second is a three-element tri-axial geophone, both of which are suitable for deployment in Australian and international coalmines.

The IS geophones are designed to interface with safe area recording equipment by means of twisted pair conductor(s) and via Zener diode barrier(s). In-line cable connectors can be used to make the handling of long cable lengths more convenient.

Anticipated benefits to the coal industry are:

· The IS geophones will allow advanced seismic techniques such as seismic tomography and microseismic monitoring to be applied underground;

· Underground seismic surveys such as seismic reflection/refraction for small geological structures and in-seam seismics will now be possible;

· Underground seismic data collection will be more cost effective and accurate than seismic exploration conducted from the surface; and

· Deploying IS geophones in hazardous zones near the working face will provide operators with much more accurate information about roof conditions and result in better informed decision making.

The geophones have been granted certification IECEx SIM 10.0011X and are available in Australia from Holville Pty Ltd, 21 Wingrove Road, Holgate, NSW 2250, Australia.