Full thrust: maintenance of industrial gas turbines

Paul Boughton

In 1852 James Prescott Joule described for the first time the physical principle of the gas turbine – the thermodynamic cycle, also known as the Joule Process. The initial ideas and concepts behind this invention date back as early as 1791.

The Swedish-based company Siemens Industrial Turbomachinery AB (SIT) manufactures gas turbines for power generation in industrial and oil and gas applications. The performance spectrum of Siemens’ industrial turbines ranges from 15 to 60 megawatts. Besides construction, the Siemens subsidiary also provides long-term service and maintenance for these engineering masterpieces. In an effort to help reduce maintenance costs, Siemens is currently working on the development and implementation of additive manufacturing technology, utilising EOS technology and equipment.

The gas turbine consists of air inlet, compressor, combustor, turbine and hot gas outlet. The compressor compresses the air going through the engine. In the combustion chamber, compressed air is mixed with fuel and burned in order to increase the kinetic energy of the flow. In the turbine, the kinetic energy of the flow is converted into mechanical energy. This mechanical energy is used to turn the gas turbine compressor and generator (to generate electricity) or other driven equipment (eg, compressor to pump the gas /oil through the pipe lines). During operations, the components in the engine’s hot gas path are exposed to high temperatures, at times in excess of 1,000˚C (eg, blades and vanes). This, in turn, leads to a high level of wear of the hot gas path components.

This is also true for the burner tip – the point at which the ignition of the fuel-air mixture takes place. Here, the effects of wear and tear can be clearly seen and measured. The manufacturer undertook rigorous testing to establish a prescribed operating period after which the burners typically need to be repaired. 

Conventional repair procedure required prefabrication of a big portion of the burner tip. This prefabricated burner tip is used for replacement of the burner tip after a specified operation time (cut old and weld prefabricated one). Conventional repair procedure can be time-consuming with a significant number of sub-processes and examinations. To help simplify and speed up the repair procedure Additive Manufacturing technology was implemented at Siemens.


Such an undertaking requires an innovative partner. Siemens found just that in EOS. In addition to having the right additive manufacturing technology, EOS was also able, within a short time frame, to individually adapt one of its in-house machines – an EOSINT M 280 – for this processing. The alterations concerned, in particular, the scale of the machine’s interior, which had to be enlarged to accommodate the 800 millimetre burner. The manufacturer also amended further hardware components such as a camera system and an optical measuring system and made corresponding adjustments to the software. EOS carried out the extensive re-working of the EOSINT system in less than a year.

From the outset it was clear that the approach would be reaping benefits. Rather than replacing a large portion of the burner tip, Siemens began by removing the damaged material only. Moreover, during repair, former versions of the burners in the fleet could be re-built to the latest design. So, theses former versions of the burners in the fleet could be not only repaired, but also improved – thus bringing new meaning to the term Additive Manufacturing.

Figures, data and facts clearly detail the success of the new repair process. Siemens Industrial Turbomachinery AB will be able to make a significant impact on the central concern – the reduction of the repair time: For the operator, what is equally important is that the turbines are quickly ready to return to service. This provides additional opportunities for potential cost reduction of the repair process – resulting in overall maintenance cost reduction.

Alongside the benefits to its own repair process, Siemens can now offer its customers strategic advantages: Through the new process, the experts are able to make improvements to the turbine technology relating to the component by building them into the repair process. In this way, operators could have access to the latest technology, even if their turbines have seen years of service.

Dr Vladimir Navrotsky, Head of Technology and Innovation at Siemens Energy Service, Oil & Gas and Industrial Applications, summarises: “With this new repair technology we are looking to carry out these high precision jobs much more quickly.” 

It's not only the Swedish Siemens’ subsidiary that views the project as a significant achievement. “We have successfully pushed our technology into the repair arena. We have shown that we are capable of modifying our system quickly to meet customer-specific requirements. In this case, the modifications to both hardware and software were significant. Everyone involved can look back with satisfaction, not only at the end result but also the route to achieving it,” says Stefan Oswald from EOS.

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