Development and field evaluation of noise controls for jumbo drills

摘要

Despite over thirty years of regulation on noise exposure, hearing loss continues to be one of the most prevalent illnesses in the mining industry in the United States. One machine used extensively in metalonmetal mines responsible for high noise exposure of its operators is the jumbo drill, used to drill holes at the mines for blasting purposes. In this context, the National Institute for Occupational Safety and Health (NIOSH) conducted research to develop noise controls for these machines. Noise source identification showed that the vibration of the drill string is the dominant source. Therefore, two different approaches were taken to reduce drill string sound radiation: vibration isolation and the addition of damping. This paper presents the development and the results of laboratory and field testing of damped drill strings by comparing the operator location sound levels when drilling with a standard drill string to the sound levels when drilling with the noise controls installed. The paper also provides a discussion of the various design parameters, including the material property selection, the dimensional constraints, and durability issues. Furthermore, the results of the field evaluation of these noise controls—in terms of noise reduction at the operator's location and drilling performance—are presented. Overall, a 3 to 5 dB reduction at the operator location was achieved with these noise controls.