In Ecopetrol-ICP was carried out an evaluation of the mechanical and microstructural properties of modified 9G--1 Mo alloy, ASTM A-335 Gr. P91, finding higher strength mechanical properties, allowable stresses and creep rupture strenght, than the conventional 9Cr-1 Mo alloy, ASTM A-335 Gr. P9, recommending the alloy P91 as substitute tube material in the radiation zone of the Visbreaking heater of Cartagena's Refinery (furnace in revamping process). The results obtained permit a thickness reduction of radiation tubes of material P91 close to 25% and increase the internal volume tube over up 8%, which is a parameter to consider in improving productivity and efficiency process. Also would be obtained a significant savings cost in the material among 5 and 1 0%. Additionally, expectations of both design and remaining useful life would be seen extensively favored with this change of alloy.
