Remnant Life Assessment of Platformer Heater T9 Tubes Using API 579 Omega Method

Tubes operated in furnaces are known to suffer from damage as a result of time dependent strain, i.e. creep. As such there is a need to predict remaining life. The MPC Omega Method has been adopted by API (API 579 “Fitness for Service”) as the standard method of life assessment and has been used to perform a remnant life assessment on a platformer furnace. Samples of T9 tubes were removed from the heater based on site inspection to determine the levels of strain. This inspection was undertaken after 224,000 hours operation at a process gas outlet temperature of 540°C. The uncertainty caused by the difference in life based either on minimum and mean material properties, indicates the necessity of proceeding to a Level 3 assessment in order to determine the actual material properties. The results of this approach using the API 579 Omega method demonstrated that the hot face material had properties within the scatter band, mid-way between the mean and minimum data lines and provided confidence as to the remaining life. The Omega approach successfully allowed the impact of variations in future operating conditions to be explored providing information to set the operational envelope and define inspection and replacement strategies.