Underground » Detection and Prevention of Fires and Explosions
This report deals with the third phase of a project with the overall objective to develop an investigation tool for use in sealed or inaccessible areas of underground coal mines. The device would gather information, mainly gas concentration data and perhaps visual information. This would aid in the rapid identification and treatment of heatings and other incidents.
The initial phase of the project, reported in 2002, evaluated the feasibility of developing such a device. Included in this feasibility study was the clarification of the need for such a device, what these needs were and what the practical limitations were. The next phase was the construction of a prototype device to demonstrate the practicality of full system development. This was reported in 2004. This focused on developing the basic cabling and deployment system, to be deployed via the borehole. Non Intrinsically Safe (IS) video cameras were utilised in this phase to evaluate the value of vision to the probe. The current project sought to develop this tool further by refining the optical systems to improve underground visibility, include the ability to measure the underground atmospheric pressure, air velocity and develop an active inert shield to render the device effectively flameproof. In addition the probe head was reduced in size in order so it could be deployed via a 100 mm borehole. The smaller borehole diameter requirement offers significant savings in time and money for drilling the boreholes.
C14017 did achieve the majority of its objectives. The basic system was extensively successfully trialled at Newstan Colliery over a five week period accessing a total of fourteen boreholes. The probe then underwent two revisions and these were successfully trialled at Newstan and two other locations in NSW. In these latter instances the camera system was used to evaluate subsidence effects of underground coal mines. Areas of mine roadway were clearly observed over 50 m away. Gas samples were taken and temperatures and pressures monitored at these locations. The vision enabled Newstan to quantify the state of seals around an old longwall goaf as well as identify a number of areas of roof fall. In addition during the application of fly ash the camera was able to assess the quality of the sealing the flyash achieved. The probe had a separate down-hole camera capability which has proven very useful for inspecting the walls of the unlined boreholes for cracks and effects of subsidence.
C14017 did not achieve all its project aims. This was due to a combination of technical difficulties and the associated time and cost increases incurred in overcoming them. In particular the complexity in building a probe capable of being deployed down a 100 mm diameter uncased borehole was underestimated. Uncased boreholes often became much narrower due to swelling of the materials lining the borehole and some blocked completely. As the borehole is uncased material can become attached to the probe and can cover the camera or lights. In addition, the probe cable became damaged due to difficulties traversing these reduced diameter boreholes and had to be shortened to 380 m to remove the damaged sections. The probe assembly was damaged on several occasions in attempting to traverse narrow boreholes. Field trials also took longer than expected due to a myriad of minor technical and operational issues such as blocked boreholes. Some elements of the probe, such as the rotation mechanism, proved to be less robust than desired. The principal researchers on this project were Associate Professor David Cliff, who has over ten years experience in dealing with mine environments and spontaneous combustion in particular and Mr John Lakeland, who has over twenty years experience in developing borehole equipment, including camera systems for inspecting boreholes. These were the principal researchers for ACARP project C11033.
An 
e-newsletter has also been published for this project, highlighting its significance for the industry.