An Investigation About Preventing
Cavitation Damage And Fatigue Failure
In Derbendikhan Power Station
Author(s)
S. S. Fattah, F. M. Khoshnaw & R. A. Saeed
Abstract
During periodic inspections of unit 2 in Derbendikhan hydropower station,
cavitation damages and fatigue cracks were observed in the runner and draft
tubes. Operation data (field data) between 1997–2002 were taken from the
station; these data included head and output. The Prototype performance curve
was obtained from the model test data and drawn by using the available
equations, charts and tables from the literature and catalogs. The results showed
that the unit 2 in Derbendikhan hydropower station operated abnormally which
led to cavitation damages and fatigue cracks. For simulating the effect of
overloading procedure on fatigue cracks in the runner, laboratory measurements
were performed using martensitic stainless steel notched specimens. Four modes
of overloading procedure are accomplished which were tension (T), compression
(C), tension-compression (TC) and compression-tension (CT). For each
overloading mode four different load values 150N, 200N, 250N and 300N were
applied. The results showed that the beneficial effect (crack retardation) was
observed under certain values for each overloading mode.
Keywords: cavitation damage, fatigue, hydropower station, overloading.
1 Introduction
The major problems in operating the hydraulic turbines are the occurrence of
cavitation and fatigue failures. Cavitations are the formation of water vapor and
air bubbles in the water due to the reduction of pressure below the vapor pressure
corresponding to the temperature of the water. The cavity bubbles collapse close
to a solid surface at regions of higher pressure, which generates highly localized
stresses. Repetition of this phenomenon for a large number of times causes local
Keywords
cavitation damage, fatigue, hydropower station, overloading.
Related Book
Other papers in this volume
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