Effects of Roof Bolter Canopy Air Curtain on Airflow and Dust Dispersion in an Entry Using Exhaust Curtain Ventilation

A recent study conducted by the National Institute for Occupational Safety and Health (NIOSH) evaluated the roof bolter canopy air curtain (CAC) system in a blowing face ventilation system, demonstrating its effectiveness and illustrating the CAC protection zones. This study evaluates the roof bolter machine CAC while operating in an exhausting face ventilation system. This study considers two similar locations to allow comparison with the previous blowing face ventilation (Zheng et al., Min Metal Explor 36(6):1115-1126, (2019)) study: (1) a roof bolter machine bolting the roof at 20 ft (6.1 m) from the face and (2) a roof bolting machine bolting at 4 ft (1.2 m) from the face. The environment introduces 6.0 mg/m(3)of respirable dust to represent the roof bolting machine operating downstream of the continuous miner. However, the exhausting face ventilation uses an exhaust curtain with 9000 cfm (4.25 m(3)/s) of air. Two roof bolter machine working positions are simulated with the use of dual drill heads in the inward position for two inside bolts and in the outward position for two outside bolts. The influence of the CAC on airflows and dust dispersion is evaluated with the CAC operating at 250 cfm (0.12 m(3)/s) with dust reductions ranging from 39.5 to 82.8%. When the roof bolter machine operated close to the face, increasing CAC airflow was required for adequate protection since the dust reductions can be as low as 39.5%. Additional CAC airflows of 350 cfm (0.17 m(3)/s) and 450 cfm (0.21 m(3)/s) were evaluated and demonstrated that dust reductions increased to 59.7% (350 cfm) and 72.0% (450 cfm) for the worst location where the roof bolter operators located.