The problem of corrosion-assisted low-pressure blade failures is discussed from the water chemistry and aerothermodynamic viewpoints. The physical chemistry of particular steam impurities existing in low-pressure steam turbines is reviewed with special applicability to blade path steam conditions. The interaction of the turbine expansion line with the salt solution zone has been verified by field testing which has, for the first time, demonstrated the existence of concentrated impurities within the low pressure turbine blade path. In addition, the existence of low levels of moisture as measured by an optical moisture probe offers strong evidence that the expansion process in low-pressure steam turbines takes place, on the average, in thermodynamic equilibrium, at least in the vicinity of the saturated vapor line.

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