Active Explosion Barriers

In recent times, the effectiveness of traditional methods of coal dust explosion suppression in underground mines has come under increasing scrutiny. Current methods are based upon the widespread distribution of stone dust in mine roadways, and the construction of various types of explosion barriers utilising stone dust or water. It has long been known that passive explosion barriers of this type are limited in the range of explosion conditions that can be successfully handled. Further, they are considered expensive, and difficult to install and maintain, particularly in a high production longwall panel.

Active explosion barriers differ significantly to traditional passive barriers by detecting the approach of an explosion and triggering the assisted dispersal of a suppression agent. Modern light detectors can be used to detect the approach of the explosion flame eliminating the reliance on pressure rise as a means of triggering, which has limited the application of active barrier technology to explosion suppression in the past.

This report reviews the application of active barrier technology to explosion suppression in coal mines. Various types of explosion barriers were examined and it was found that recent developments in South Africa would permit the development of a feasible alternative to traditional explosion barriers for installation in mine roadways. These types of barriers would provide a considerable improvement to the effectiveness of roadway explosion barriers by suppressing any explosion much sooner thereby reducing the development of pressure and toxic atmospheres in a mine.

An analysis of typical costs associated with the construction of various types of explosion barriers was undertaken. This showed that costs were mainly determined by whether the barrier was a stone dust or water barrier and whether there was a requirement to move the barrier as the face position changed. The most expensive barrier was a stone dust barrier as described by the Queensland regulations that was required to remain within a set distance of the mining face. For a 2000m gateroad development this was calculated to cost about $228,000. An equivalent water barrier was calculated to cost about $86,000. It was estimated that the costs of installing and maintaining an equivalent active barrier would be about $17,000 for a 2000m development.

To demonstrate the application of the South African technology to the development of a viable active roadway barrier a program of test work has been suggested and considered by industry stakeholders.

A review of the current knowledge on practical coal mine explosion suppression is included in the report.