Preservation & Maintenance Techniques of Boilers in Thermal Power Plant

Preservation & Maintenance Techniques of Boilers |Boiler Preservation Practices | Boiler Preservation Procedures in Thermal Power Plant | Short/Long Term Preservation
The primary purpose of the cycle chemistry is to provide protective oxide surfaces on all components throughout the steam and water circuits; the primary purpose of the shutdown and layup periods should be to maintain those protective surfaces.
Severe corrosion damage to all power plant cycle components has been experienced because of insufficiently protected metal surfaces during inactive periods. Examples of such damage include the following:
Turbine blade and disk pitting;
Boiler drum and tube, feedwater heater, and condenser pitting and oxidation; and
Stress corrosion of condenser and feedwater heater tubing in stagnant oxygenated water.
Corrosion damage can occur on the water and steam-side surfaces as well as on other surfaces, including pipe surfaces under insulation.
The generation of excessive amounts of metal oxides and the contamination of layup water, if used, with oxygen and carbon dioxide adversely influence water and steam chemistry during subsequent startup and operation. The effect is prolonged startup period.
Other considerations of layup include its cost (chemicals, equipment, manpower) and the proper disposal of layup water when practicing wet layup and using chemicals such as ammonia and hydrazine.

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