DS EN 1759-4:2003 Flanges And Their Joints - Circular Flanges For Pipes, Valves, Fittings And Accessories, Class Designated - Part 4: Aluminium Alloy Flanges Defines requirements for Class designated circular flanges for pipes, valves, fittings and accessories made from aluminium alloy in the range of DN 15 to DN 600 (NPS 1/2 to NPS 24) and class 150 to Cl