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# Wall thickness calculation according to ASME B31.3 + PED 2

## Wall thickness calculation according to ASME B31.3 + PED

(OP)
What is the formula for calculating the thickness in compliance with both ASME B31.3 and the European Pressure Equipment Directive (PED)? While ASME B31.3 has more conservative allowable stresses for carbon steel materials compared to PED, the guidelines for austenitic materials are not as clear.
Replies continue below

### RE: Wall thickness calculation according to ASME B31.3 + PED

You need to expand on this and provide the different formulas and constants and where int he two documents you're looking.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Wall thickness calculation according to ASME B31.3 + PED

The formula(e) are independent of the code. However, for austenitics, you may be required to 'lower' B31.3's allowable stress from table A-1(M) if the material under consideration doesn't meet the elongation requirements from PED Annex I Para 7.1.2, second indent. They don't always meet B31.3 para 302.3.2(d)(3).

Work is under way to update/expand B31.3 Appendix N and Appendix S on this very subject to better inform Code users.

Huub
- You never get what you expect, you only get what you inspect.

### RE: Wall thickness calculation according to ASME B31.3 + PED

(OP)
I am currently preparing a piping class. For the calculation of wall thickness, I will utilize the formulas provided by ASME B31.3. As for the determination of allowable stress and joint efficiency, I will select the more stringent requirements between PED and ASME B31.3. Please let me know if this approach aligns with your expectations.

### RE: Wall thickness calculation according to ASME B31.3 + PED

I wouldn't do that, that's make it overly conservative. For JE (in B31.3 piping classes that need to meet PED) we refer to the following default not in all piping classes;

#### Quote:

The joint efficient factor according to PED 2014/68/EU annex I §7.2 is not required to be applied, since it deals with longitudinal butt weld seams. Refer to harmonized standards EN 13480-3:2017 §4.5 and EN 13480-5:2017 §8.3 for argumentation.

For the allowable stress Id look into the specific ASTM specs, and determine at forehand if you're in the troublezone. If you are, and you have cat II or greater (thus NoBo involvement), determine with your Nobo how they look at this specific item. Some NoBo's are strict, whereas others understand this is a ridiculous requirement - nevertheless, its law, so if a NoBo requires it, just go with the flow..

Huub
- You never get what you expect, you only get what you inspect.

### RE: Wall thickness calculation according to ASME B31.3 + PED

I know that technical guideline. It can be useful in a lot of points, however, I wouldn't use it as a basis to take the conservative route; instead, look for technical valid arguments to do the opposite. Its complete bullocks that pipe x, which has MAWP y, all of a sudden will have a lower MAWP z when it's used under PED category I or higher.

Huub
- You never get what you expect, you only get what you inspect.

### RE: Wall thickness calculation according to ASME B31.3 + PED

(OP)

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