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. 2012 Dec;64(12):64-70.

Evaluations of a noise control for roof bolting machines

A S Azman  1 , D S Yantek  1 , L A Alcorn  1
Affiliations

Evaluations of a noise control for roof bolting machines

A S Azman et al. Min Eng. 2012 Dec.

Abstract

In collaboration with Kennametal Inc. and Corry Rubber Corporation, the U.S. National Institute for Occupational Safety and Health (NIOSH) developed a drill bit isolator to address noise overexposures associated with roof bolting machines in underground coal mines. NIOSH laboratory studies confirmed that the drill bit isolator reduces noise during drilling. Field studies were needed to confirm that a noise reduction could be obtained under working conditions and that the device was sufficiently durable. This paper reports results of field tests of the device conducted at five underground coal mines. Noise reduction was assessed by comparing the operator's noise exposure during drilling with and without the drill bit isolator. Durability was assessed by recording the number of holes and total feet drilled with each bit isolator until either the test period ended or the device failed. The results from these tests showed that the device is an effective noise control in a mine environment. The field-tested drill bit isolators provided a noise reduction of 3-5 dB(A). Of nine devices tested for durability, five exceeded 610 m (2,000 ft) drilled and two exceeded 762 m (2,500 ft) drilled before failure. Durability issues found in the field tests led to final production optimizations that have resulted in a commercially available product for drilling with 35-mm- (1.3-in.-) diameter roof bits and hexagonal drill steels.

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Figures

Figure 1
Figure 1
Diagram of the prototype drill bit isolator detailing the various components.
Figure 2
Figure 2
Drill bit isolator installed with 35-mm (1.3-in.) drill bit and hexagonal drill steel.
Figure 3
Figure 3
Closeup of inner and outer members of the drill bit isolator, showing the location of the isolating rubber layer.
Figure 4
Figure 4
Gap between inner and outer cylinder of the drill bit isolator for normal function (left) and after bottoming out from high axial loading (right).
See this image and copyright information in PMC

References

    1. Michael R, Yantek D, Peterson J, Ferro E. The evolution of drill bit and chuck isolators to reduce roof bolting machine drilling noise. SME Annual Meeting and Exhibit; February 28-March 3; Phoenix, AZ. Littleton, CO: Society for Mining, Metallurgy, and Exploration, Inc; 2010. p. 7. preprint 10–104.
    1. Michael R, Yantek D, Johnson D, Ferro E, Swope C. Development of elastomeric isolators to reduce roof bolting machine drilling noise. Noise Control Engineering Journal. 2011;59(6):591–612. - PMC - PubMed
    1. NIOSH. Equipment noise and worker exposure in the coal mining industry. Pittsburgh, PA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH); 2006. Publication No. 2007–105.
    1. Peterson J, Alcorn L. Results of noise measurements from underground testing of a roof bolting machine duty cycle. Proceedings of Noise-Con; 2007.2007.
    1. Tak S, Calvert GM. Hearing difficulty attributable to employment by industry and occupations: An analysis of the National Health Interview Survey—United States, 1997–2003. Journal of Occupational and Environmental Medicine. 2008;50:46–56. - PubMed

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