Developing Additive Manufacturing Technology for Burner Repair

Low emission combustion is one of the most important requirements for industrial gas turbines. Siemens industrial gas turbines SGT-800 and SGT-700 use dry low emission (DLE) technology and are equipped with third generation of DLE burners. These burners demonstrate high-performance and reliable operation for the duration of their design lifetime. The design and shape of the burner tip is of great importance in order to achieve a good fuel/ air mixture and at the same time a resistance to the fatigue created by heat radiation input. This gives a requirement for a tip structure with delicate internal channels combined with thicker structure for load carrying and production reasons. It was found that the extension of the burner lifetime beyond the original design life could be accomplished by means of repair of the burner tip. Initially, the tip repair has been done by conventional methods— i.e., cutting off the tip and replacing it with a premanufactured one. Due to the sophisticated internal structure of the burner, the cuts have to be made fairly high upstream to avoid having the weld in the delicate channel area. Through the use of additive manufacturing (AM) technology, it has been possible to simplify the repair and only replace the damaged part of the tip. Special processes have been developed for AM repair procedure, including the following: machining off of the damaged and oxidized tip, positioning the sintered model on the burner face, sintering a new tip in place, quality assurance and inspection methods, powder handling, material qualification including bonding zone, development of methods for mechanical integrity calculation, and qualification of the whole repair process. This paper describes how we have developed and qualified SGT-800 and SGT-700 DLE burners repair with the help of additive manufacturing technology and our research work performed. In addition, this paper highlights the challenges we faced during design, materials qualification, and repair work shop set up.