Necessary calorific energy, during the in-service welding of pipelines for petroleum transport

The thermal behavior during in service repair welding of oil transportation pipes was studied by finite element analysis in the present paper. Regression equations that relate peak temperature at the inner surface of the pipe and cooling time between 800 and 500 degrees C in the heat affected zone to the welding heat input, preheat temperature, and convection heat transfer coefficient were obtained The former parameters govern, respectively, the possibility of burn through and cold cracking, and the latter parameters define the thermal behavior during welding. The existence of conditions that simultaneously satisfy the obtained equations, for different combinations of related variables, was proved. Graphical representations of relevant practical importance that were developed from the solution of obtained equations are presented.