2017DIN EN 558:2017 Industrial valves - Face-to-face and centre-to-face dimensions of metal valves for use in flanged pipe systems - PN and Class designated valves; German version EN 558:2017
1991DIN EN 26554:1991 Flanged automatic steam traps; face-to-face dimensions (ISO 6554:1980); german version EN 26554:1991