Butterfly Valves for Cement & Mining

For cement raw meal slurry pipelines, the recommended butterfly valve specification is a rubber-lined (natural rubber) wafer or lug butterfly valve with these key characteristics: (1) Ductile iron body (ASTM A536 Grade 65-45-12) - ductile iron's superior impact toughness vs. standard cast iron prevents cracking from pipeline surge and water hammer; (2) Natural rubber (NR) one-piece moulded seat and disc facing - NR 50-60 Shore A provides the best combination of abrasion resistance and sealing performance for cement slurry; the seat and disc face should be replaceable as a liner assembly to extend valve life; (3) Full-bore or near-full-bore disc design - a concentric butterfly valve disc creates a pocket that accumulates slurry and causes hard-spot buildup on the seat; high-performance eccentric (offset) disc designs flush more cleanly; (4) Heavy-duty stem with PTFE stem bearings - not standard brass bushings, which will corrode and seize in alkaline cement slurry (pH 9-12); (5) Pneumatic or electric actuator sized for abrasive slurry torque (add 30-50% to clean-water torque) - slurry settles on the disc face when the valve is stationary, creating high breakaway torque; (6) Compliance with AWWA C504 for water-based slurry service larger than DN200. Avoid: high-performance butterfly valves with PTFE seats in raw meal slurry - PTFE has very low abrasion resistance and will wear rapidly from slurry particle impact.

Yes, but only triple-offset (triple-eccentric) metal-seated butterfly valves are suitable for kiln cooling air above 200°C. The key requirements for cement kiln air service at 400°C are: (1) Triple-offset geometry - the three offsets (shaft offset from disc centreline, shaft offset from body centreline, and cone angle) mean the disc seats and unseats with a cam-like motion rather than wiping contact. This prevents the metal-to-metal seating surfaces from galling and eroding from abrasive cement dust; (2) Metal seat ring - typically SS 316L or SS 410 seat ring with Stellite 6 overlay for wear resistance; no elastomers (all rubber, PTFE, and EPDM seats fail above 200°C); (3) Carbon steel body (A216 WCB) for temperatures to 550°C - confirm ASME B16.34 pressure-temperature tables for the specific service conditions; (4) Graphite packing - graphite stem packing is required for continuous high-temperature service; PTFE packing is limited to 260°C; (5) High-temperature disc material - A351 CF8M (SS 316) disc or A182 F6a (13Cr) disc for oxidation resistance in hot air with fine cement dust at 400°C; (6) Extended bonnet or finned bonnet - in some cases where stem packing temperature must be limited, an extended bonnet moves the packing away from the hot process. API 609 Category B (triple-offset) is the appropriate standard for this high-temperature kiln air service.