Abstract
Testing was completed on an earlier roof bolter CAC that used slots to provide a perimeter airflow. NIOSH tested it due to its unique design that differed from canopies that provided uniform airflow. Based upon NIOSH recommendations from the earlier testing, a 3rd generation roof bolter CAC has been developed by J.H. Fletcher & Co. The changes to this CAC involve design modifications to the plenum outlets, using a single row of outlets on the perimeter and a different material for the plenum. This laboratory testing was a continuation of the original perimeter slotted CAC design. Using gravimetric and instantaneous sampling of respirable dust concentrations underneath and outside of the CAC, the laboratory testing was completed using three different blower fans that delivered differing airflows. The maximum plenum airflow velocities ranged from 2.34 to 3.64 m/s (460–716 fpm). Results showed plenum respirable dust concentrations ranging from 34.6% to 49.3% lower than respirable dust concentrations outside the plenum protection zone, thus showing an improvement in protection for the roof bolter operators.
Highlights
Based on recent statistics in the U.S, following a low point in the late 1990s where the prevalence of coal workers’ pneumoconiosis (CWP) in miners with 25 years or more tenure was approximately 5%, CWP exceeds 10% for miners with 25 years or more of tenure
Results showed plenum respirable dust concentrations ranging from 34.6% to 49.3% lower than respirable dust concentrations outside the plenum protection zone, showing an improvement in protection for the roof bolter operators
The last testing completed by National Institute for Occupational Safety and Health (NIOSH) was for a canopy air curtain (CAC) design which included a slotted perimeter which anticipated providing airflow to protect the roof bolter from exposure to coal mine respirable dust (Reed et al 2017)
Summary
Based on recent statistics in the U.S, following a low point in the late 1990s where the prevalence of coal workers’ pneumoconiosis (CWP) in miners with 25 years or more tenure was approximately 5%, CWP exceeds 10% for miners with 25 years or more of tenure. The last testing completed by NIOSH was for a CAC design which included a slotted perimeter which anticipated providing airflow to protect the roof bolter from exposure to coal mine respirable dust (Reed et al 2017). The lab test results of the early perimeter design CAC demonstrated the CAC provided only up to 24.5% reductions for roof bolter operator coal mine respirable dust exposure (Reed et al 2017). These results indicated that there was an opportunity for improvement. While it is still used at some locations, the 2nd generation CAC was short lived and was quickly replaced with the 3rd generation designed CAC
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