Modernization of Existing US Navy Steam Turbines: Efficiency, Reliability and Maintainability Available to Purchase

Earlier steam plant design requirements for the US Navy steam turbines were focused on reliability and maintainability. Simplicity of design implied easy operation, maintenance and service. Efficiency was not a top priority. Now, in an atmosphere of operating budget cuts and skyrocketing fuel costs along with environmental responsibilities, efficiency improvements are expected, and in some cases demanded on main propulsion units. Additional load due to modern electronic combat systems places extra demand on SSTG sets. Modernization with improved efficiency, reliability and maintainability, while retaining design simplicity is the optimal solution. Meanwhile during the last 50 years, the turbomachinery industry has developed numerous innovative improvements through extensive R&D efforts, advanced computerized simulation of aerodynamics and flow field analysis along with finite element modeling, new manufacturing methods and improved metallurgy and surface treatments. These advances allow efficiency improvements without adding complexity to the design. Modern airfoil design, the optimized transition from partial-arc to full-arc steam admission, tangential leaning vanes, advanced seal designs, streamlined steam path configuration and improved moisture removal are major areas worthy of consideration. Mechanical reliability can be improved with Taumel (orbital) peened tenons for blade packets or integral shrouds which give a 360 degree connection to all of the blades in a row. Electron beam welded diaphragms with EDM cut horizontal joints help to minimize thermal distortions and flow irregularities, particularly at the split lines. Improved welding procedures for casing, diaphragm and rotor repairs can result in shorter repair cycles and lower costs to further promote extension of the turbine’s life cycle. Maintainability can be improved with advanced materials that no longer require regular service, such as anti-lube (greaseless) bushings and replaceable components that don’t require in place machining. Combinations of the above improvements have been used successfully within the industry in upgrading hundreds of turbines, compressors and pumps in various applications including power generation, petrochemical, oil and gas, commercial marine, and other fields. Typical examples of efficiency improvement are 8%–14% over current operating parameters. [1, 2, 3, 4, 5] This paper presents various proven advanced turbine components used to upgrade existing steam turbines, which can be successfully used in US Navy applications as well.