On December 7, 1981, at approximately 2: 50 p.m., a coal dust explosion occurred on the south main working section at the No. 11 Mine, Adkins Coal Co., located at Kite, Knott County, Kentucky. The accident resulted in the death of all eight miners who were underground at the time. The accident occurred while the face and right crosscut were being blasted simultaneously from the solid in the No. 1 entry of the active working section.
MSHA investigators concluded that a coal dust explosion occurred when a blown-out shot from the right corner blasthole of the No. 1 entry face on the south main section ignited coal dust that had been put into suspension by the blasts of this face and the face of the right crosscut.
Coal dust deposited on the floor, roof, and ribs from previous mining operations was also placed into suspension by the blasts, igniting and contributing to the propagation of the explosion. The blown-out shot occurred in the last hole in the sequence of shots that were initiated by delayed electric blasting caps having a nominal delay time of 25 to 700 ms. The blown-out shot was caused when the second hole from the corner failed to completely detonate, leaving the corner hole overburdened. The remainder of the partially failed hole, 1.88 m (74 in.) in depth, contained a continuous train of undetonated explosives without a blasting cap or stemming.
Conditions and practices that contributed to the explosion and its propagation include:
- Charging each blasthole with about 2.72 kg (6 lb.) of explosives and using a 22.7 kg (50-lb.) case to blast each face.
- Slitting the paper wrappings around the explosive cartridges before inserting them into the blastholes, tamping the deformed cartridges into the holes, and blasting without stemming.
- Not applying water, with or without a wetting agent, or other effective methods, to coal dust on the ribs, roof, and floor, particularly at distances less than 12.2 m (40 ft.) from the face, to reduce dust dispersibility and to minimize the explosion hazard.
- Not applying sufficient quantities of rock dust to the mine surfaces to render the coal dust inert to prevent the explosion from propagating.
- Permitting coal dust (including float coal dust) and loose coal to accumulate along the entries in the working section in areas immediately outby and in entries developed to the left of the section loading point.
- Failure to install and maintain line brattices or other approved devices in the working places to remove the coal dust that was dispersed into suspension when coal was blasted from the solid in the faces of the entries and connecting crosscuts.
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