Siemens has delivered for the first time in the 10 MW class a steam turbine that operates almost entirely without lubricants. The bearing systems consist of completely oil-free, air-cooled, electromagnetic bearings. The valve actuators operate with only a minimum oil supply and are controlled via software-controlled electric motors. The trial run of the first turbine equipped with magnetic bearings was successfully completed in Vattenfall’s lignite-fired Jänschwalde steam power plant, located in the southeast of the German state of Brandenburg, after which the model SST-600 steam turbine was officially handed over to Vattenfall. The turbine, says Siemens, has been running reliably in regular full-load operation since February 2015, at speeds of up to 5700 rpm. It is used as a feedwater pump drive.
Steam turbines equipped with magnetic bearings are more environmentally friendly, as they use nearly no oil, and also offer substantially better fire protection. The design also increases efficiency, by up to one per cent, because its bearings are frictionless
The first SST-600 steam turbine with magnetic bearings was developed in co-operation with the University of Zittau/Görlitz. This co-operation included the design, setup, operation and testing of a common test bay to demonstrate the feasibility of a steam turbine equipped with magnetic bearings.
"This project is a good example of successful cooperation in research and development between industry and the University of Zittau/Görlitz and represents the culmination of many years of close cooperation between Siemens Görlitz and Vattenfall", commented Prof. Dr.-Ing. Frank Worlitz, scientific director of Mechatronics Systems at the University of Zittau/Görlitz.
Siemens was responsible for technical project management of the test bay and the prototype project, for design of the steam turbine, design of the magnetic bearings and for the construction, commissioning and trial operation of the magnetic bearing steam turbine.
From a technical standpoint and depending on specific operating requirements, other Siemens steam turbine models with a rotor weight up to 10 tonne and a capacity between 45 kW to 40 MW could also be equipped with magnetic bearing systems.