B31.3 allows not to include average axial stress in displacement stress range calculations because of its insignificant magnitude in ordinary piping configurations. However in special conditions where these have significant value like double wall pipes the Code requires to consider these stresses (Para 319.2.3c), but is silent about how to "consider" these stresses. Does the Code have intent to treat these stresses same as ordinary displacement stresses comparing these with the allowable stress range given in Para 302.3.5d? However following goes against this assumption
1- The stresses are not localized
2- Elastic Shakedown is not guaranteed because of instability of pipe under compression
If these are valid concerns then how to evaluate these stresses?