Material selection steam turbine

As steam temperatures increase, more expensive materials must be used to manufacture the turbine. Above 750" F, the price increase will be about 5% to about 850°F. Another 5% will be added for temperatures between 850°F and 900°F, and another 5% for temperatures above 900°F Steam turbine designers have selected as a standard for single-stage turbines a limit of 600 psia and 750°F maximum inlet steam conditions. 

Strength to weight considerations are important in rotating components such as in steam turbines. The cost of material is often a wrong consideration, leading to the selection of the cheapest material and poor component reliability. Typical components where the selection of the least expensive material leads to poor rehability include condensers and feedwater heaters. 

The design of a turbine, especially of the multistage type, involves a great many factors that must be evaluated and considered. A detailed study of the steam path must be made, and various fiictional and leakage losses that tend to decrease the efficiency, as well as compensating factors such as reheat and carryover, must be computed and accoimted for in the final analysis of the performance of the turbine. Stresses must be calculated to permit correct proportioning of the component parts of the turbine, and materials suitable for the various requirements must be selected. 

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