Dust Control Handbook for Industrial Minerals Mining and Processing

Figure 5.21. Depiction of two types of pneumatic conveying systems.Since positive pressure pneumatic systems are totally enclosed, dust emissions do not usuallyoccur unless the system has worn-out areas. Because maximum wear in the conveying ductworkoccurs at elbows, long-radius elbows made of heavy gauge material should be used. Numerousstyles of wear-resistant elbows are available (Figure 5.22). The elbows can also be lined withrefractory or ceramic material to further reduce wear and abrasion. In low-pressure pneumaticsystems, dust may also leak through joints. Self-adhesive neoprene gaskets should be used at alljoints to provide a dust-tight seal.Figure 5.22. HammerTek wear-resistant elbow installed in conveying ductwork.Dilute phase pneumatic conveying systems operate under pressure and require some mechanicalmeans, such as a rotary valve or double dump valve, to provide an airlock and prevent transportair from short circuiting into the feed material storage bin (Figure 5.23). These types of devicesemploy moving parts and seals that are often subject to high wear and significant maintenance.Conveying and Transport 151