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8

DEFLECTION

I I .
2000 4000
TIME TO FAILURE(DAYS)
Fig. 7. Time to fatigue failure versus spindle deflection.

compressive stresses (by shot peening) have remained in HP heater water chambers after 5 years at
270°C.
Finally, it has been shown that thread re-profiling and shot peening can mitigate fatigue failure
in valve spindles. Also regular checks of actuating system out-of-alignment should be carried out
together with good insulation at key locations which should help minimise thermal distortions.

REFERENCES

1. Amzallag, C. and Maillard, J. L., 9th Inter. Conf. Structural Mechanics in Reactor Technology, Smirt, Lausanne,
Switzerland, Aug. 1987, Vol. F, pp. 173-180.
2. Gauchet, J. P., Reversat, C., Leguernic, Y., Lebrun, J. L., Castax, L. and Barrallier, L. K., EDF Feedback on French
Feedwater Plants Repaired by Shot Peening, EPRI Inter. Conf. Welding & Repair Technology for Fossil Power Plants,
March 1994, Williamsburg, Virginia, U.S.A.