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Thermal Power
Welding Solutions for Thermal Power Generation
The development and production of heat and creep resistant welding consumables for power plant applications are a focus of voestalpine Böhler Welding. Additionally, we support the manufacturers with our far-reaching experience in the welding of creep resistant steels. Fontargen Brazing provides filler metals and fluxes for the brazing in the generators and transformers. voestalpine Böhler Welding produces TUV-approved welding consumables for the base metals most used in thermal power plants.
The matching filler metals for the creep resistant steels and alloys are tested under creep conditions at elevated temperature. The creep tests have been performed on both all weld metal specimens and weld joints.
Welding of Steam Generators and Boilers
A: Superheaters / Reheaters
Superheater and reheater tubes are necessary to convert wet, saturated steam into dry steam. These tube bundles are located within the combustion chamber of the boiler. voestalpine Böhler Welding offers top quality high alloyed welding consumables that, depending on the operating conditions, are required to guarantee resistance against heat and corrosion.
B: Headers
Headers are thick-walled extruded pipes in which the fluids carried by the tubes are mixed and homogenized. These heavy-section components have to meet creep strength requirements. voestalpine Böhler Welding offers welding consumables for the high-quality welding of these critical components.
C: Main steam / Hot reheat piping
Main steam and hot reheat piping are thick-walled seamless pipes which transport the dry steam from the headers to the turbine. The wall thickness of these pipes is up to 100 mm. voestalpine Böhler Welding offers the proven welding consumables necessary for this application, which is highly demanding due to the high temperature (up to 620°C) and pressure (up to 350 bar).
D: Water walls (or membrane walls)
Many kilometers of tubes and fins are welded together and form the outside wall of the boiler. Different tube and fin material is used depending on the design of the boiler, the capacity, the temperature and the pressure (e.g. T1, T12, T23, T24...). voestalpine Böhler Welding offers welding consumables for the mechanized welding of these components in SAW or GMAW/FCAW processes as well as for the tube-to-tube welds that are necessary as performed in GTAW process (manual or auto).
Welding of Steam Turbines
Special steels and special welding consumables are required for highly stressed components such as valves, turbine housing and rotors.. Heavy steel castings and rotor forgings, made of creep resistant steels, play a key role in fossil fuel fired power plants for highly loaded components in the high and intermediate pressure sections of a turbine casting. Turbine and generator rotors withstand high stresses and are the most significant components of a turbine generator system from a safety point of view.
Combinations of different steels are used for the welded rotors. Depending on the operating temperatures, the shafts can be fabricated out of creep resistance material or of highly toughened material.
The welding of low-pressure shafts require matching filler metals. Combined intermediate-low pressure shafts and combined high-low pressure shafts are welded using different steels. These dissimilar welded joints are designed to be located in low stress shaft areas. For this reason, the strength requirements for these welded joints are lower than for the base material. On the other hand, impact energy values of the weldments are even higher than minimum base material values. Creep is not a problem for the low-pressure end of the rotor, but high yield strength, high ductility and low Fracture Appearance Transition Temperature (FATT) behavior is required.
voestalpine Böhler Welding offers tailor-made solutions for the specific customer requirements regarding different steel combinations.
Welding of Flue Gas Desulphurization Units
Depending on the application, FGD units require high corrosion resistant steels and Ni-alloys, for tanks, piping, absorbers, etc. The materials selection criteria depend on the chloride and pH concentration. In general, the flue of lignite coal fired power plants is more aggressive than that of hard coal fired power plants. Therefore, the FGDs of a lignite coal fired power plant generally needs high corrosion-resistant Ni-base alloys with increased CPT values.
Depending on the requirements, voestalpine Böhler Welding offers welding consumables higher alloyed than the base material, in order to match the base material corrosion resistance properties compensating the effect of the dilution.
