During shutdowns, all equipment must be preserved in the 'As Left' condition till there is a need to activate them. When needed, they should be capable of going 'On-Line' immediately.
When a power plant is not in operation, many components within the plant are subject to corrosion. Corrosion occurs due to the presence of moisture in the air. Moisture accelerates the rate of corrosion leading to malfunctions and the deterioration of parts and components such as Turbines, Power Generators, boilers, condensers etc.Rate of corrosion accelerates, when Relative Humidity crosses the critical level of 40%.