Calorific Energy Required During In-Service Welding of Pipelines for Petroleum Transport

The thermal behaviour during in-service repair welding of oil transportation pipes was studied using finite element analysis in the present paper. Regression equations that relate peak temperature of the inner surface of the pipe and cooling time between 800 and 500°C in the heat-affected zone to the welding heat input, preheat temperature and convective 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 behaviour during welding. The existence of conditions that simultaneously satisfy the equations obtained, for different combinations of related variables, was proved. Graphical representations of relevant practical importance, developed from the solution of obtained equations, are presented.