API St 609 pdf download Butterfy Valves: Double-fanged, Lug- and Wafer-type, and Butt-welding Ends 1.1 This standard covers design，materials,face-to-face dimensions， pressure-temperature ratings,andexamination, inspection, and test requirements for gray iron, ductile iron, bronze, steel, nickel-based alloy, orspecial alloy butterfly valves. 1.2 The following two categories of butterfly valves are included: a) Category A—Manufacturer’s rated cold working pressure (CWP) butterfly valves, usually...