Assessment and evaluation of noise controls on roof bolting equipment and a method for predicting sound pressure levels in underground coal mining

Development of Drilling Control Technology to Reduce Drilling Noise during Roof Bolting Operations

“…Noise control treatments related to roof bolting machines were provided in this report, which included modification to the dust collection blower or changing to quieter model, covering or enclosing the hydraulic pump and sealing the enclosure around the motor and pump-blower drives using existing cover panels. After the application of most of the recommended controls by the manufacturers of roof bolting machine, the noise exposure of the operator still exceeded the regulatory limits when conducting the drilling or bolting installation process (Matetic, 2006).…”

“…Noise-induced hearing loss (NIHL) has been identified by NIOSH as one of the ten leading work-related diseases and injuries (Matetic, 2006). .1 Percent with hearing impairment among coal, metal/nonmetal miners and nonnoise exposed group (Matetic, 2006) The roof bolting operation is one of the noisiest underground mining operations.…”

“…The roof drilling task was determined to be the most significant contributor to the operators' noise exposure during the roof bolting machine duty cycle. Matetic (2006) proposed research to assess and evaluate noise controls on roof bolting equipment and predict sound pressure levels in underground coal mining. In his research, the sound power levels radiated by a roof bolting machine during different drilling configurations and utilizing differing types of drilling methods in high compressive strength rock media were measured in the Pittsburgh Research Laboratory (PRL).…”

“…Table 2.1 Full octave band (Bise, 2001))……………………………....………………… Table 2.2 Comparison of drilling noise control methods (Lowe et al, 2010)…..….17 Table 4.1 Preset drilling parameters…………………………………………….……40 Table 5.1 Raw data collected from the roof bolter control system………………...……. 45 Table 5.2 Measured and calculated drilling parameters based on raw data……….…….. 46 Table 5.3 A typical sample of noise dose…………………………………….……..…... 50 Table 5.4 Dust sample collection in the fourth set of drilling tests……………………... 79 Table 5.5 Average particle size for drilling tests at different bite depth…………..…….. 82 viii Figure 1.1 Percent with hearing impairment among coal, metal/nonmetal miners and non-noise exposed group (Matetic, 2006) Chuck isolator (Peterson et al, 2009))……………………………………… 16 Figure 2.2 Roof bolting noise control methods (CDSE) (Matetic et al, 2008) and redesigned CDSE (Azman et al, 2014)…………………………..…..……... 17 xii Figure 5.37 Cumulative volume percent of dust smaller than 74 μm for 7/8 hex drill steel ……………………………………………………………………………………...….. 84 Figure 5.38 Size distribution of dust smaller than 25 μm for 7/8 hex drill steel……….. 86 Figure 5.39 Size distribution of dust smaller than 5 μm for 7/8 hex drill steel…….…… 86 Figure 6.1 Drill control algorithm…………………………………………….…….. 89 Figure 6.2 Required specific energy for various unconfined compressive strength (Luo et al, 2002)………………………………………………………………………….91 Noise induced hearing loss is a severe health issue in the United States mining industry. Mine workers are exposed to high noise level through the use of heavy equipment in the confined work environment underground.…”

“…About 24.3% of mine workers are reported to have hearing loss, which is second only to the railroad industry (Tak & Calvert, 2008). About 80% of the nation's miners are working in an environment where the time weighted average (TWA) noise level exceeds 85 dBA and more than 25% of the miners are exposed to a TWA noise level that exceeds 90 dBA, the permissible exposure limit (PEL) (Matetic, 2006). A NIOSH study of a large sample of audiograms also indicated that about 65% of coal miners suffered hearing impairment at age 55, compared to only 10% of the non-occupationally exposed group of the same age ( Figure 1.1).…”