Cold Bending of A335 Gr.P9 Tubes of Heaters of Catalytic Reforming Unit of Lavan Oil Refining Compan

The platformer heaters of catalytic reforming unit of Lavan oil refining company include the Threeheaters of the Box Heater type with Arbor coil. The tubes used in these heaters are made of ASTMA335 Gr.P9 with a diameter of 3 inches and a thickness of 5.49 mm. Generally the hot bendingmethod along with a preheat up to a temperature of about 900-1020 °C and subsequently normalizingtempering heat treatment after bending is the conventional method which is used in the world as well as by the main heaters’ manufacturer for the bending of these tubes. However in order to replace thetubes of the heaters of Lavan oil refining company with a bending radius of 1524 mm and a bendopening of 180 ° and a length of 2959 mm and because of operational force for backing the heaters inservice the by preparation of a procedure by Lavan Oil Refining Company experts, cold bendingmethod with a preheat temperature of about 180 °C followed by a stress relief heat treatment at 690 °Cfor 20 min was used. Since this bending method was not common in the past and was performed inIran for the 1st time, in order to ensure the validity of the above method, destructive tests includingcold tensile test, hot tensile test at the design temperature of the heaters (609 °C), Brinell hardness test,macroscopic and microscopic examinations were used and compared with the results of similar testson straight tubes in both pre- and post-Stress relief conditions.In addition non-destructive tests ofmagnetic particle test and portable hardness test as well as dimensional examinations were performedon all bends. According to the comparisons between the results of the destructive tests, the leastchanges in the microstructural and mechanical properties at room temperature and design temperaturewere observed between the bending part and the straight part of the tubes and the correctness of thisbending method was confirmed. Finally, the bended tubes were installed and put into service in theheaters of Lavan Oil refining Company on March 2018 and now they are in service with no problem.and properly after about four years continuously

Cold Bending of A335 Gr.P9 Tubes of Heaters of Catalytic Reforming Unit of Lavan Oil Refining Compan Keywords:

cold bending , stress relief , Cr-Mo steel , heater , oil refinery