The methods of determining burnthrough risk have changed over the years. The first burnthrough limits were developed experimentally and then, with the development of computers, came computer models. The first major advancement in computer models came at Battelle, in the early 1980s, with the development of the “Hot-Tap Thermal-Analysis Models.” The Battelle models use two-dimensional numerical solutions to predict the inside surface temperature as a function of the welding parameters, pipe parameters, and the operating conditions. The Battelle model considers an inside surface temperature of less than 1800°F (982°C) when using low-hydrogen electrodes, [1400°F (760°C) when using cellulosic-coated electrodes] to be safe. Since the release of the Battelle model, introduction other models have been developed which are based on Battelle’s logic as well as other approaches. PRCI, as well as others, has funded research to develop an alternative burnthrough prediction model which is based on a thermo-mechanical approach taking into account the stress associated with pressurized pipe. These alternative approaches differ from Battelle’s criteria which only uses the inside surface temperature as the lonely determining factor of safe welding practices.

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