Laboratory evaluations of a 25-mm drill bit isolator to reduce noise from roof bolting machines in underground coal mines

摘要

Roof bolting machine noise is a significant health hazard in underground coal mining because the sound levels at the operator station often exceed 100 dB(A). Drilling the hole prior to installing the roof bolt is the most significant source of operator exposure. The drill steel is the dominant noise source during this operation. NIOSH has developed a noise control to mitigate this exposure. The drill bit isolator is designed to fit in line with the drill bit and drill steel. It is made of two steel cylinders with an elastomer material between them, designed to damp the vibrations of the drill steel as it drills a bolt hole. This noise control is currently commercially available for drilling with 35-mm drill steels. A smaller version, used with 25-mm drill steels, has been laboratory tested at OMSHR facilities and shows a reduction of 2-4 dB at the operator position when drilling in granite. The evolution of the device as well as laboratory evaluations are described in this paper. Field evaluations are underway and final steps are being taken to bring the 25-mm drill bit isolator to fruition as a commercially available noise control.