Maintenance, Repair & Overhaul – Review and outlook

What was the project about?
By combining standardized manufacturing with state-of-the-art technologies such as additive manufacturing processes and digitization (e.g. digital twin), the team was able to digitize and automate individual process steps and network them to some extent. In Phase II, among other things, the interfaces of the individual solutions are to be completely networked in order to be able to offer customers customized solutions with increased added value in the future. The research project was officially launched in the summer of 2020 and despite all the adversities of the pandemic, the team was able to successfully report its milestones for the sixth time in January 2023. Thanks to the technical expertise of the research partners and SMEs, as well as the excellent collaboration in all work packages, Phase I was completed successfully and according to schedule.

Results from the project have been presented at the Innovation Network Panel in November 2022 and at the Milestone Meeting in January 2023, among other events. The presentation of the project in posters as well as numerous other publications by the project team can be found on our website under Publications.

What results were achieved?
Digitization: The MRO digitization work packages focused on issues surrounding the digital twin and its various interfaces. For example, in MRO DI 1 “Digitization of the recording of findings”, the prototype of a photo table (see Figure 1: Photo table) has been completed, with which the external damage pattern of a gas turbine blade can be recorded with AI support. Using 5 cameras and 2 different component orientations, the entire component surface can be photographed in 10 images and analyzed using artificial intelligence (AI) to detect and mark surface findings. These defects can then be projected onto a 3D surface model of the component to enable a semi-automated CAx repair chain.

Furthermore, in DI 7 “Worker assistance systems”, the prototypical worker* workstation has been realized. Here, the component position on the work table is detected using AR, cameras and beamers, and defects that are to be processed by the worker are displayed or made recognizable on the component and work-relevant information is displayed. This eliminates the time-consuming manual search for component and job information.
The “digital twin” (MRO DI 6) has been designed and is being implemented. Interfaces to the individual MRO process steps were defined and resulting requirements for required or generated data were derived. These requirements are in turn used to define and implement the physical connection of the twin to the Siemens Energy internal IT architecture through an AWS cloud solution. This enables data networking of the entire MRO process chain and acceleration as well as maximum transparency of the refurbishment process.

Additive manufacturing: Within MRO, we developed hybrid repair approaches for gas turbine blades based on LPBF (Laser Powder Bed Fusion) and LPW (Laser Powder Welding) technologies depending on the application. By means of LPBF the upper 10% of turbine blades shall be rebuilt. Through such a repair process, it is possible to simultaneously optimize the printed additively manufactured structure and keep the geometry always up to date with the latest research. Since conventional LPBF printers were not designed for such an application, the following problems arise:
1: Spatial determination of the component in the build space of the system.
2: Quality control of the build process.
3: Incorporation into a suitable manufacturing flow / pre & post processes.
Using LPW, local areas (troughs) can be welded automatically. Due to the varying defect patterns, an adaptive geometry detection system, which automatically detects troughs, was therefore developed. The spatial data of the trough are then used to generate a weld path.

New materials: Within MRO, we developed an approach for damage analysis of gas turbine blades. For this purpose, we investigated material data on crack propagation in joining zones of repaired components. The focus was on three repair/jointing processes: Additive Manufacturing, Narrow Gap Brazing (NGB), Pre-Sintered Preforms (PSP). These material data and further field data from the gas turbines are to be evaluated with the aid of an AI and combined in Phase II into an AI-based damage prognosis, which can be used to make a statement in advance about the possibilities and scope of a refurbishment.

What’s next?
Project manager Daniel Koch (Siemens Energy AG) commented: “We are picking up where we left off. I am very pleased to see how we have grown together as a consortium and successfully implement the tasks as a team and then now also begin to industrialize them in our on-site production”. It is very pleasing that the existing team, strengthened by 2 additional SMEs “YOUSE” (were involved as subcontractors in Phase I) and “SERVITIZE”, as well as 2 additional departments each from the TU Berlin and BAM, can start immediately with Phase II of the MRO 2.0 project. The 2nd phase is entitled “Upgrade instead of classic repair” and aims to completely network the process steps digitized in phase I in order to thus optimize the processes in the repair of gas turbines so that customers can receive a blade back after repair with improved functionalities compared to the delivery condition. In addition to networking, Phase II will focus on “human-machine interaction” and “sustainability”. In the area of additive manufacturing, we are focusing on automated repair of large turbine blades using robotic Wire Arc AM (WAAM). In the area of materials, we will work on a work package that does not deal with the turbine blades but with the combustion chamber bricks, raising the question of how to improve the water vapor resistance of these ceramic materials in hydrogen firing.
We will report more about the 2nd phase on our website soon.

Both project phases are funded by Investitionsbank Berlin (IBB), co-financed by the European Regional Development Fund (EFRE).