Dust Control Handbook for Industrial Minerals Mining and Processing

The integrity of the drill deck shroud and its sealing capability to the ground are critical factorsin the effectiveness of a dry collection system for medium- to large-diameter drills. Over half ofthe dry dust collector emissions are from shroud and drill stem bushing leakage [USBM 1985].Openings or gaps greater than six inches between the drill deck shroud and ground cansignificantly diminish the dust collector's inlet capture effectiveness [USBM 1986; Zimmer et al.1987]. Three areas of vulnerability have been identified related to dry dust collection:deck shroud leakage,collector dump discharge, anddrill stem/deck leakage.Deck Shroud Leakage SolutionsWith the exception of air track drills, most rock drills have the same basic configuration andcollector airflow volumes. The only parameter that varies is the shroud leakage area, and suchvariances obviously change the capture efficiency. Some of the most common shroud enclosureopenings are between the bottom of the shroud and ground, caused by uneven or sloping drillbench surfaces and at the corners of the drill deck.Rectangular ShroudSome shrouds have gaps at the corners of the front side of the shroud, which can be hydraulicallylifted up so that drill cuttings are not dragged over the hole when the drill moves with its boomup. Because most deck shrouds are rectangular and constructed from four separate pieces ofrubber belting attached to the deck, leakage can also occur as the seams separate from oneanother. To combat this problem, corner flaps can be added, attached with brackets, to helppreserve the integrity of the shroud (see Figure 3.5), or the shroud can be constructed with asingle piece of material (rubber belting) encompassing the drill deck perimeter.Figure 3.5. Reinforcing flaps added to each corner ofa rectangular deck shroud to reduce leakage.Drilling and Blasting 85