Jens/Billy/Rien,
The NEN working group has clarified the correct pipe diameter for the assessment of deflection. For the assessment of ovalisation (vertical deflection and 'piggability') of steel pipes, the new design standard Draft NEN 3650-2:2025 uses the average diameter Dg, see screenshot below. When the NEN 3650-2:2026 code is released end Q2/begin Q3 the sources in PLE needs to be changed everywhere where the ovalisation calculation is used. For the General analysis method the avarage diameter should also be used according to other material NEN 3650 codes then steel (NEN 3650-2).
Source: Draft NEN 3650-2:2025