B31.4 - Max Pressure Allowable vs. 12.5% Wall reduction

[shopper1732]

I have an electronic copy of B31.4 and am going blind trying to confirm that Maximum Pressure Allowable per the Barlow Formula is based on pipe with a maximum wall thickness of 87.5% of nominal wall because of manufacturing tolerance of -12.5%.

I am looking for a paragraph that says that after calulating the minimum required wall thickness, and then selecting a suitable Schedule for the pipe, that the (negative)12.5% manufacturing tolerance must be taken into account.

Why can't I find this in the ASME B31.4

 

[metengr]

The underthickness tolerance is mentioned in paragraph 402.3.1 in the 2002 Edition of ASME B31.4. The 0.72 factor used to calculate the allowable stress for use in determining design wall thickness per the equation in 404.1.2 for straight pipe under internal pressure takes into account the 12.5% underthickness tolerance.