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| Case Analysis of Fatigue Cracking on the Weld of Sampling Connection of Main Coolant Lines |
| Received:October 15, 2015 Revised:April 15, 2016 |
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| DOI：10.7643/issn.1672-9242.2016.02.018 |
| KeyWord:main coolant lines hydrostatic test weld toe fatigue cracking |
| Author | Institution |
| LIANG Xia-xiang |
China Nuclear Power Engineering Co.， Ltd， NI Equipment Design Dept， Shenzhen ， China |
| DUAN Yuan-gang |
China Nuclear Power Engineering Co.， Ltd， NI Equipment Design Dept， Shenzhen ， China |
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| Abstract: |
| Objective According to unacceptable linear indications by liquid penetrant examination on the weld of sampling connection of main coolant lines after hydrostatic test during manufacturing, the failure causes were analyzed, the formation and propagation mechanism for rarely seen fatigue cracks during manufacturing was explored, and the alternating stress source of fatigue was discussed. Methods In the paper, macroscopic analysis, optical microscope and scanning electron microscope were used. Results The results showed that the material quality was acceptable and the linear indication was caused by fatigue cracks. Conclusion The multi-source crack in the weld toe of the sampling pipe was not caused by hydrostatic test, but was fatigue cracking resulted from the excessive alternating current load near the weld toe of the sampling pipe caused by improper cutting during the removal of the plug via mechanical machining after the hydrostatic test. The fatigue stress came from the cutting process of plug after the hydrostatic test. Unreasonable milling was the key factor leading to fatigue crack. |
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