Design and Efficiency of Dust and Water Barriers in Modern Australian Coal Mines

The objectives of the first stage of this project which has now been completed were to examine the strengths and weaknesses of current stonedust and water barrier designs as they apply in Australian coal mines and to begin to identify if improvements might be made and what further research would be necessary to enable them. The first stage has largely centred on a wide literature review to determine the parameters under which barriers operate.

Some of the key findings of this work are that:-

• Current Australian general stonedusting regulations and practice incorporate small safety margins in cases of very strong explosions and review of them is justified.
• Size distribution of stonedust requires experimental review.
• Nevertheless, general stonedusting, when properly applied, appears to be the most reliable combative solution to explosion propagation in coal mines.
• Passive explosion barriers will not provide protection for personnel in and near the flame initiation zone.
• Passive barriers are unlikely to arrest methane explosions at the coal face, weak coal dust explosions, explosions of hybrid mixtures of methane and dust, or very strong explosions.
• Weak coal dust explosions can propagate in well stonedusted roads if there is a film of as little as 0.2mm of coal dust present on top of the inerted material.
• Stonedusting inbye of passive barriers can reduce the chance of them operating effectively by reducing the strength of the explosion as it reaches them. This issue requires further consideration.
• There is no evidence to suggest that changing the location of passive barriers as currently specified in regulations will improve their reliability.
• There is evidence to suggest that the use of distributed barriers may be more effective for explosion suppression, but these are not permitted by all regulations at present.
• The effectiveness of passive barriers is further compromised by the presence of equipment such as monorail systems and conveyor belts in the barrier zone.
• Because ignitions at the face in continuous miner development headings may lead to development of powerful dust explosions there is a case established to investigate the use of small triggered barrier devices fitted to continuous miners.

The report goes on to make recommendations for future research directions which may be pursued if Stage 2 of this project takes place. The results of Stage 1 provide ample information to establish a case for review of existing regulations and practice both for the continued use of passive barriers and current general stonedusting practice.