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Welding on in-service pipes can be completed under various codes depending on the application and the jurisdiction where it is performed.聽聽One of the common requirements of these codes is that for welding on pipe with a thickness of less than 1/4鈥� (6.4mm) that the potential for burn-through be controlled.聽聽In this paper, some of the common simulation and calculation methods that are used to predict burn through are reviewed and discussed.聽聽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.聽聽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.