Continual service reassurance of steam turbine blades
Journal
Engineering Failure Analysis
Journal Volume
3
Journal Issue
2
Pages
95-102
Date Issued
1996
Abstract
This paper describes a practical case of the successful application of fracture mechanics principles to evaluate turbine blade integrity that led to the saving of a considerable sum of money. Cracks up to 24 mm were detected in some steam turbine blades of a nuclear power generating unit after being in operation for one year. New blades were installed. To ensure safety, the regulatory body required these new blades to be reinspected nine months later during the middle of the nuclear fuel cycle. The reinspection date fell in the peak demand summer season. Owing to a shortage of reserve electricity generating capacity, there were practical difficulties in stopping operation and opening the turbine casing for inspection. A conservative fracture mechanics analysis was carried out to show conclusively that the blades were safe under the current operating conditions. Considering limitations in the resolution of non-destructive inspection, the analysis started from assuming a pre-existing crack. Fatigue crack growth and fracture under different operating conditions were then considered to arrive at a conservative estimate of the blade life. Following reviews and discussion, the regulatory body agreed that reinspection could be postponed to a convenient date. It was estimated that such a postponement helped to save at least 20 million dollars in direct revenue. Extra savings in reserve energy cost and downstream economic advantages due to the avoidance of cutting the electricity supply have not yet been included. Copyright © 1996 Elsevier Science Ltd.
SDGs
Type
journal article