Mining Project: Noise Controls for Jumbo Drills Used in Metal/Nonmetal Mines
To develop durable noise controls that reduce the noise exposure of jumbo drill operators and facilitate the commercialization of the controls to make them available for all miners.
Jumbo drill operators are exposed to some of the highest noise levels in metal/nonmetal mining. In the worst cases, they can experience noise levels in excess of 105 dB(A). In such instances they are overexposed to noise in less than 60 minutes and are highly likely to incur permanent hearing loss. Based on data provided by the Parker Bay Company & Raw Materials Group, which does market research on mining equipment, NIOSH estimates that about 50% of the jumbo drill machines used in the U.S. do not have cabs; therefore, operators are directly exposed to the noise generated by the machine.
To help address this problem, this project had three research aims, as follows:
- Determine the most significant contributors to the noise generated by jumbo drills during operating conditions.
- Develop durable engineering noise controls for jumbo drills that focus on the most significant noise-generating mechanisms and reduce jumbo drill operator exposures.
- Facilitate the commercialization of the engineering noise controls developed for jumbo drills.
This project sought to develop noise controls that reduce exposure while not interfering with effective operation of the jumbo drill. Engineering noise controls were developed to reduce the sound levels generated by jumbo drills. The effectiveness of these controls was evaluated in a laboratory setting and also in an underground setting to assess the reduction in worker exposure. The goal was to reduce the noise exposure for jumbo drill operators and crew by at least 50 percent.
The jumbo drill drifter and drill string were confirmed as prominent noise contributors to the sound level at the operator location. Several different prototype noise controls to address these noise sources were fabricated and tested under laboratory and field conditions. These noise controls include damped drill strings and damped drill string centralizers. Several versions of each were laboratory and field tested. An additional noise control, a drill string snubber, was also laboratory and field tested. NIOSH is continuing laboratory and field testing of noise controls as an intervention evaluation to determine their final designs.
The impact of this research will be to reduce the likelihood and magnitude of hearing loss for jumbo drill operators. The amount of reduction will vary with operating conditions, but in many instances the noise controls should reduce the noise exposure of the operator.
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