Fatigue Life Assessment of Bourdon Tube against Cyclic Internal Pressure

Since Bourdon tubes are small in size and complicated in geometry, an ordinary fatigue design procedure is difficult to be applied, in which the design fatigue curve of the component material and the stress analysis of the component based on the operation mode are necessary. Therefore, the entire coil configuration was used to evaluate the integrity against fatigue of the Bourdon tube. The fatigue resistance property of the Bourdon tube was directly obtained by applying cyclic internal pressure (Pa), which simulates the internal pressure fluctuation during the normal operation of the Bourdon tubes in BWR power plants. As a consequence, a reasonable fatigue design margin was demonstrated for the proposed exchange period of 4 years, of the Bourdon tubes in BWR power plants by extrapolating Pa-Nf (fatigue life) curve according to the Modified Miner's and Haibach's methods, and by the evaluation procedures recommended in the ASME Code, Sec.III, Appendix II.