In conjunction with roof bolter manufacturer JH Fletcher, the US research agency has developed a collapsible drill steel enclosure, or CDSE, designed to enclose the drill steel of a bolter as the unit is drilling.

“Noise-induced hearing loss is a prevalent occupational illness in the United States; studies indicate that 70 to 90 per cent of miners have NIHL significant enough to be classified as a hearing disability,” the researchers explained, adding that federal mine officials’ studies have indicated that roof bolter operators are among those overexposed.

“Field studies support the premise that, on average, drilling is the loudest noise source to which a roof bolting machine operator is typically exposed and contributes greatly to the operator’s noise exposure [and] NIOSH has further determined that the drill steel and chuck radiate a significant amount of noise during drilling.”

The device was designed to be easy to use, and to allow the operator to see the drill steel to ensure the holes are lined up. Additionally, the individual can easily monitor for steel bowing while performing bolting operations.

As the drillhead nears the roof, the CDSE collapses. It also swings out of the way so that normal roof bolt installation can be performed.

NIOSH said that field tests of the device had been positive, showing a reduction in time-weighted noise exposure from drilling noise of up to 7 decibels.

“Laboratory testing in a reverberation chamber (for sound power level) and hemianechoic chamber (for noise source identification and operator ear sound pressure level) showed that the CDSE reduces the noise level at the roof bolting machine operator location, thus reducing noise exposure,” the agency said, noting the results were confirmed in additional field testing at a cooperating mine.

The CDSE can be easily retrofitted onto any roof bolting machine.