Handbook for Methane Control in Mining - AMMSA

57Cecala and Jayaraman [1994] have provided a detailed design andinstallation manual for the modified shearer-clearer system. It isavailable as a free pdf download from NTIS 6 as PB95104873.Figure 4–3.—Methane concentration at shearer during tail-to-headpass.Figure 4–4.—Plan view of walkway and gob curtains (shearer notshown).Methane accumulationsduring the headgate cutout.Ventilation at the shearer alsosuffers and the methane concentrationrises as the shearermakes the headgate cutout(Figure 4–3). This rise inmethane takes place because theair flowing down the headgateentry does not readily make the90° turn as it reaches the longwallface. Thus, a portion candivert to flow through the legsof the first 8–10 supports.Because of this air diversion,the amount of air flowing overthe shearer is not sufficient toavoid methane buildup. Thisbuildup can be prevented with awalkway curtain.The walkway curtain [Cecalaet al. 1986], used to force moreair over the shearer body duringthe headgate cutout, is shown inFigures 4–4 and 4–5. The curtainshould be located across thewalkway near support No. 3,extending from the support legsto the spill plate reaching fromthe roof to the floor. To beeffective, it must be used inconjunction with a gob curtain,a dust control device already inuse at most longwalls (Figure4–4). The walkway curtainraises the air velocity over theshearer by 23% at the headgate6 National Technical Information Service, Springfield, VA. See www.ntis.gov.