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| High-explosive boosters ready to be lowered into a blasthole |
Description of Problem
During 1996-1999, there were three blasting accidents involving a single type of detonator and booster. In one case, the detonator and booster detonated in the blaster's hands during assembly. The other two cases involved booster/detonator assemblies that initiated by impact at the bottom of a blasthole. Two blasters were killed and one injured in the three accidents.
Research and Development Activities
The Mine Safety and Health Administration asked explosives researchers at the Pittsburgh Research Laboratory (PRL) to assist in the investigation of these accidents. A borehole from the surface to the Bruceton Research Coal Mine was used to simulate a typical blasthole at a mine. Simulated boosters with detonators were dropped down the borehole to simulate two of the accidents. Impact geometry was varied to understand how the boosters may have detonated accidentally. Drop weight impact tests were conducted on the boosters and detonators to identify any unusual sensitivity to impact. Tests were conducted at Lake Lynn Laboratory to simulate what might happen if the detonator gets stuck in the booster and a blaster tries to pry it out with a knife. The findings showed that the accidents most likely occurred because the detonator well in the booster was partially plugged with foreign material such that a detonator could not be fully inserted, placing the detonator in a more exposed and hazardous position.
R&D Outputs and Transfer Activities
In 2000, PRL explosives researchers met with the manufacturer and the company's consultant. NIOSH researchers recommended that the booster be modified to incorporate a piece of tape over the detonator well to keep out foreign material.
Description of Intermediate Outcome
The manufacturer modified the specifications for its boosters according to NIOSH recommendations. Since the modification was made, there have been no further accidents involving this type of detonator and booster.