Underground » Detection and Prevention of Fires and Explosions
ACARP Project C14027 Active Explosion Barriers, has been undertaken as part of a programme to demonstrate the feasibility of suppressing a coal dust explosion by the deployment of an active explosion barrier as opposed to traditional passive explosion barriers. Coal dust explosions will always represent the most significant hazard in an underground coal mine. Without some means of limiting the extent of combustible dust accumulations in the mine, or some means of preventing the propagation of an explosion a coal dust explosion is capable of causing significant damage and loss of life.
Traditional methods of limiting the extent of combustible accumulations in a coal mine are based on the application of large quantities of stone dust (crushed limestone or other carbonate mineral) so as to render the mixture of coal dust and stone dust incombustible. This requires continual renewal of the stone dust as fresh coal dust accumulates in the mine roadways.
The other traditional method of coal dust explosion management is the installation of passive explosion barriers. These consist of a series of shelves of stone dust or tubs of water mounted in the mine roadway in such a way that the shelves/tubs are easily dispersed or broken by the initial pressure wave associated with the coal dust explosion. This adds a significant quantity of stone dust or water into the coal dust cloud developing ahead of the flame front to render the resulting dust cloud incombustible and prevent the continued propagation of the flame.
There are a number of "deficiencies" with traditional methods of coal dust explosion management:
Stone dusting requires continual renewal;
Constant vigilance to maintain adequate levels or concentrations of stone dust;
Passive explosion barriers also need constant maintenance to maintain an effective distance between the face and the barrier.
These deficiencies could be addressed with the deployment of an active explosion barrier.
An active barrier works by detecting the approach of the explosion flame front and triggering the rapid release of an explosion suppression agent in front of the flame. This project was conceived to verify the simulation outcomes from CFD Modelling of explosions in the CSIR Kloppersbos Tunnel and to determine the operational requirements of a prototype active explosion barrier for testing in the Kloppersbos experimental explosion tunnel in South Africa.