Controlling the Potential for Burn-Through on Thin-Wall In-Service Piping

Welding on in-service pipes can be completed under various codes depending on the application and the jurisdiction where it is performed.  One of the common requirements of these codes is that for welding on pipe with a thickness of less than 1/4” (6.4mm) that the potential for burn-through be controlled.  In this paper, some of the common simulation and calculation methods that are used to predict burn through are reviewed and discussed.  Due to these methods predicting failure where the prevention of burn-thorough is possible, modified tests for welding procedure qualification of thin wall in-service application are proposed.  By controlling key process parameters such as weld heat input, cooling rate, welding sequence and good workmanship, the modified procedure was used in qualification of some example projects, and was safely used in application.