Within a temperature range of 200...250°C (feed water), dissolved oxygen causes corrosion of components and piping, i.e., Condensers, Low pressure preheaters, Feed water tanks, High pressure preheaters and Economizers. The resulting pitting may eventually cause puncturing and failures.
Dissolved oxygen also promotes electrolytic action between dissimilar metals causing corrosion and leakage at joints and gaskets.
To minimize corrosion under alkaline operating conditions, mechanical deaeration and chemicals scavenger additives are used to remove the dissolved oxygen. An analytical check of process efficiency, therefore, is essential.
Dissolved oxygen monitoring is imperative in power stations using neutral or combined operating conditions (pH 7.0-7.5 or 8.0-8.5). The typical points in steam circuit where dissolved oxygen monitoring is required are . Condenser outlet, L.P. heaters, Economizer inlet.