No. 1022
	Diagnosis Methods and Countermeasures against Deterioration of Hydro-turbines
	Technical Committee of Survey on Diagnosis Methods and Countermeasures against Deterioration of Hydro-turbines
	Against the background of slowing power demand growth and progressing market liberalization, the longer durability and more reasonable maintenance are required for equipment in hydropower plants. Thus, with an aim to elongate the frequency of inspections, which involve disassembling and repairing equipment, the maintenance work has been changing from the traditional Time Based Preventive Maintenance (TBM), wherein inspections are planned on the periodical basis, to the new Condition Based Preventive Maintenance (CBM), wherein inspections are planned on the basis of the condition of equipment. For the introduction of CBM, however, as it is necessary to accurately assess the deterioration condition of parts and the materials condition of equipment ,the standardizing diagnosis methods and criteria has been required. For this purpose, this committee surveyed cases of deterioration and defects in parts and materials of hydro-turbines concerning the diagnosis methods and marginal strength of materials as well as performance and repair timing in order to clarify the diagnosis methods and criteria for hydro-turbines. The committee also surveyed the latest technologies of the external diagnosis devices and the durability extension methods in order to help maintenance work hereafter. This report is mainly composed of the following items. (1) Current practices (frequencies and contents of inspections; criteria for repair and replacement; parts and materials subject to deterioration; cases of decay, corrosion, erosion, crack and other troubles) (2) Diagnosis methods for repair and replacement of parts and materials of hydro-turbines (criteria for repair and replacement; measurement and control of material wear and loss; nondestructive testing; external diagnosis technologies) (3) Durability extension methods for hydro-turbines (welding; coating; improving materials; optimal design; preventive measures against crack development)
	©2005. The Institute of Electrical Engineers of Japan