what is the formula to calculate the thickness of a pipework according to ASME B31.3 but in compiliance with the Europian pressure equipment directive PED?
The thickness assessment methods for piping and piping components as stipulated in ASME B31.3 is not comparable with the methods as per PED.
European Norm (EN) 13480 describes it's own methods of wall thickness determinations.
The end user may select the design code, but mixing of codes is not allowed.
The PED itself is a law not a Code . It does not contain formula's. ASME B31.3 can be used for wall thickness calculations because the safety factors used for allowable stress determination in ASME are equal or more concervative than required by the PED.
I agree with ijzer. ASME B31.3 can be used to demonstrate that the essential safety requirements of the PED are satisfied, but it's best to involve your Notified Body early on, if one is required by the category classification, to ensure all bases are covered.
The advantage of using EN 13480 is that (as a harmonised standard) it provides a presumption of conformity with the PED, without any further argument.
Just a side issue on the mixing of design codes - PED does not actually forbid this, it is just up to the user to highlight how the essential requirements are covered by the various parts used, and to verify there is no incompatibility or inconsistency between them - see Guideline 9/6 at
Regarding the mixing of codes I meant its not allowed to use the design stress of the EN into the ASME B31.3 wall thickness calculation or the other way around, if used as a benefit.
Nor is it allowed, as far as I'm aware, to use requirements for PWHT according EN (32mm), and base your design upon ASME (19mm).
That's what we have experienced with our NOBO.
Yes, it would be difficult to demonstrate compatibility in that case.
We've had vigorous discussion regarding the application of the PED pressure test requirements with regard to pressure vessels, where the PED requirement exceeds that of ASME VIII Div 1, following the argument that the code requirements should be followed in their entirety. But the B31.3 test pressure exceeds that dictated by the PED, so there is no problem in that respect for piping designed to B31.3.
