This International Standard specifies the requirements for metallic butterfly valves — with centred or eccentric disc, — with centred or eccentric shaft, — with metallic, polymeric, elastomeric or composite seating, — with lined or unlined body, — coated or uncoated, to be used in flanged or butt-welded piping systems for shut-off, throttling or flow control. It covers butterfly valves with nominal diameters DN 40; 50; 65; 80; 100; 125; 150; 200; 250; 300; 350; 400; 450; 500; 550; 600; 650; 700; 750; 800; 900; 1 000; 1 200; 1 400; 1 600; 1 800; 2 000; and is applicable to valves of nominal pressure PN 2,5; 6; 10; 16; 20; 25; 40; 50.