Butterfly valves regulate flow via a quarter-turn disc in wafer, lug or flanged bodies from DN50 to DN2400. Ductile iron, SS304/316 or carbon steel with EPDM/NBR/PTFE/Viton seats deliver bubble-tight shutoff, low torque, minimal pressure drop and corrosion resistance. Manual lever, gearbox, pneumatic or electric actuation fits water, HVAC, chemical, marine and power lines under DIN/ANSI/JIS/EN.