API 599 pdf download.Metal Plug Valves—Flanged, Threaded and Welding Ends 1.1 SCOPE 1.1.1 This standard covers steel, nickel base and other alloy plug valves with ßanged or butt-welding ends and ductile iron plug valves with ßanged ends in sizes NPS 1 / 2 through NPS 24 and threaded or socket-welding ends for sizes NPS 1 / 2 through NPS 2....