The region surrounding Germany’s capital has an agile energy engineering cluster. The gas turbine producer Siemens, whose manufacturing technology is undergoing an innovation process, is a key player within this sector. 3D print and laser technology are also revolutionising the industry in Berlin-Brandenburg.
In Berlin, Siemens is building the biggest and the most powerful gas turbines in the world. Since 1972, the gas turbine plant Berlin has shipped almost 1,000 gas turbines to customers in more than 60 countries around the world. In the combined gas and steam operation, the most efficient Siemens model, the so-called SGT5-8000H, achieves an efficiency of more than 61%. Thus, a power plant of this type can provide electricity for the entire population of Berlin. However, the pace of innovation on the gas turbine market has quickened significantly. Innovative manufacturing technologies such as the “3D print ” help develop new products and make the existing gas turbine fleet even more efficient and more powerful.
Everybody is talking about 3D print. Whether it is chocolate, action figures or pasta – by now all imaginable shapes from almost any material can be “printed” using this technology. The field of power generation using fossil fuels, however, is one of the most challenging fields of application for this relatively young technology. The inside of the gas turbine has to withstand extreme stresses. The rotor, the heart of the gas turbine, weighing up to 120 tons rotates at 3,000 (50Hz market) or 3,600 (60Hz market) RPMs. Here, the blades are exposed to temperatures of more than 1,500°C, hence temperatures close to the melting point of iron, while at the same time centrifugal forces act on the blades, which equate to 10,000 times their own weight. These examples demonstrate the tremendous demands the material has to meet. And this aspect is what makes 3D print a unique challenge. Thus, Siemens is one of the first companies that manufactures components for power plant gas turbines using additive manufacturing processes.
In order to turn a digital model into a physical component, the so-called Selective Laser Melting (SLM) process is used. Here, a complete 3D component is created layer-by-layer from a 3D CAD model. The 400-watt laser in the SLM machine melts the metallic powder particles, which on average are no larger than 40 µm, layer-by-layer.
“Freedom of Design.” The infinite possibilities for design provide a huge advantage. Components which could not be produced using conventional manufacturing methods, such as casting, welding and lathing, are suddenly realisable using SLM. Complex geometries, such as filigree cooling air ducts in the interior of a turbine blade or a burner head: There are no limits to new design approaches thanks to 3D technology.
Rapid Prototyping. That’s why the SLM process is primarily used for developing prototypes. New design ideas can be turned into actual components and checked within no time. In order to test and validate the new components even quicker, Siemens opened a new combustion systems test centre, the Clean Energy Center (CEC), in February 2015 in Ludwigsfelde. In the test centre, located a 40-minute drive to the south of Berlin, the combustion and the respective measuring technology of small and big gas turbines is checked and validated. Combustion technology is a key technology when it comes to efficiency, performance and emissions of gas turbines. At the CEC, combustion processes can be analysed and optimised in detail. The company test centre also makes it possible to conduct test runs independent of external verification bodies. This is faster and more cost-effective, and ensures know-how protection, than appointing external institutions to conduct the tests.
After the component tests have been completed successfully, the new models are tested in the company test bay or at the customer site in a fully assembled system. Testing and validating is thus integrated into the entire development process and no longer used for the final check of the design approach. Prototypes can be manufactured and assessed within a few months. This equates to a reduction of the development cycle of 75%.
Rapid Repair. Siemens uses the SLM technology in the field of gas turbine production, but not for manufacturing prototypes. By now, certain components, such as burner heads of the SGT-1000F series, can be produced in series and are used in service for maintenance and repair work. The replacement of a wear part can be done in a considerably shorter amount of time – time that immediately benefits the customer.
Vision of the future. Due to the quality of today’s SLM machines and the high stresses that the components of the gas turbine operation have to withstand, there are still limitations regarding the size and the material of the components. In the future, printing blades from highly heat-resistant materials, which not only withstand short-term tests at the CEC or at the test facility, will pose a major challenge. In the not too distant future, however, blades are to be printed from heat-resistant material in order to use them in gas turbines permanently.
The new manufacturing technology has already shown one thing: The accelerated innovation process results in huge savings in terms of development time and allows for innovative technological improvements. This way, Siemens customers receive efficient, flexible and environmentally-friendly gas turbines.
Having studied Mechanical Engineering, Andreas Fischer-Ludwig has been part of the Siemens Group since 1987. During this time, he worked in various management positions in strategic and technical units. As head of Manufacturing Development & Industrialization, he is currently responsible for the future topic of Selective Laser Melting (SLM) for large gas turbines of the Siemens AG. Fischer-Ludwig is a member of the management of the gas turbine plant in Berlin.