ČSN EN 558

This European Standard specifies the "face-to-face" (FTF) and "centre-to-face" (CTF) dimensions for PN and Class designated metal valves used in flanged pipe systems.
This European Standard covers valves with the following PN, Class and DN values:
- PN 2,5; PN 6; PN 10; PN 16; PN 25; PN 40; PN 63; PN 100; PN 160; PN 250; PN 320; PN 400;
- Class 125; Class 150; Class 250; Class 300; Class 600; Class 900; Class 1 500; Class 2 500;
- DN 10; DN 15; DN 20; DN 25; DN 32; DN 40; DN 50; DN 65; DN 80; DN 100; DN 125; DN 150; DN 200; DN 250; DN 300; DN 350; DN 400; DN 450; DN 500; DN 600; DN 700; DN 750; DN 800; DN 900; DN 1 000; DN 1050; DN 1 200; DN 1 400; DN 1 600; DN 1 800; DN 2 000.
For valves in other shell materials than metal the same FTF and CTF dimensions may be used.
For relationship between DN and NPS see Annex B.