Recently introduced into Australia, ACIRL-CSIR Bag Barriers have taken off in New South Wales underground coal mines.

The technology, developed at the Kloppersbos explosion testing centre of the CSIR in South Africa, offers an alternative to traditional water and shelf stone dust barriers. ACIRL has the licence to sell the technology in Australia and has supplied 13 underground coal mines to date. The stone dust is suspended from any appropriate point, such as roof supports by specially made plastic bags and suspension hooks.

ACIRL said full-size testing at the Tremonia experimental mine found a minimum dynamic pressure of 3kPa ruptures the bags.

"This is much lower than the 20kPa for conventional water or stone dust barriers, allowing properly constructed bag barriers to suppress weaker explosions that would not activate conventional passive barriers."

ACIRL said bag barriers were versatile and provided better protection in roadways containing obstructing equipment. "For example, the shielded areas below conveyor belts can be protected against explosion propogation by suspending bags on the conveyor frame. This is impractical with water troughs or shelf type dust barriers."

The average longwall can spend several hundred thousand dollars installing and regularly relocating current barriers. Subject to height constraints, the bag barriers can be installed along the entire gateroad during development. ACIRL said, owing to the low replacement cost, there was no requirement to interrupt production to reposition the explosion barrier or to recover any material during retreat.