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Titanium is being used for steam turbine blading on a limited basis throughout the world. Most applications involve large, low pressure steam turbine blades where the high strength-to-weight ratio of titanium is particularly suited to limiting centrifugal stresses. Titanium blades are also used in steam turbines because of their superior corrosion resistance. Corrosion, stress corrosion, and corrosion fatigue can occur in the moisture transition region of some fossil low pressure steam turbines. Westinghouse and the Electric Power Research Institute initiated a development program in 1979 to investigate the use of titanium, particularly in the moisture transition region of low pressure turbines. The result of this project was the installation and telemetry testing of a row of 16 inch transition stage blades in the Martin Lake station of TU Electric in December, 1984. The blades successfully passed all testing, and are still operating in the Martin Lake 3 machine. More recently, TU Electric decided to replace the transition row blades in all of the Martin Lake machines. One of these additional rows of blades experienced cracking in April, 1987. One titanium blade cracked to separation and 19 other titanium blades were found cracked in this incident. A subsequent investigation was unable to find any material related or manufacturing related causes for the incident. The incident was attributed to aerodynamic instability of the blade which lead to high stresses and eventual cracking. |
