The Standard Diameter Ratio (SDR) is a key dimensional characteristic used for pipes. It is defined simply as the ratio of the pipe's Outer Diameter (OD) to its wall thickness.
Definition and Application
SDR = OD / wall thickness
In many calculations, particularly for pressure pipes, the mean diameter (OD minus wall thickness) is often used, leading to expressions involving SDR-124. For example, the SDR is a crucial parameter in Barlow's formula used to calculate the pressure rating (PN) of a pipe.
The values for the Outer Diameter used in ISO standards for pipes are often ISO values +1, related to the SDR definition. The ISO standard uses so-called Renard or ISO figures for OD, materials strength, and safety factors, based on constant percentage steps.
While the source defines SDR and shows its use in formulas, it does not detail the calculation process itself.