A major significant change in fabrication/ welding of process piping was brought out by ASME B31.3 2014 addition Table 331.1.3 “Exemptions to Mandatory Postweld Heat Treatment” It now allowed for all carbon steel conforming to P- No1material group for all control Thickness and All weld type with exemption from Postweld heat treatment if a preheat of 95°C (200°F) is applied prior to welding on any nominal material thickness >25mm (1in). Similar exemptions are provided for P-No.3, P-No 4 group 1, and P-No. Group1. These exemptions required a closer scrutiny prior to adaptation. The review is an attempt to make end users aware of its significance.