Cause analysis of cracking of brass connecting nut of circuit breaker

Liming Xie; Feng Tian; XinAi Guo

doi:10.1117/12.2640856

24 October 2022 Cause analysis of cracking of brass connecting nut of circuit breaker

Liming Xie, Feng Tian, XinAi Guo

Proceedings Volume 12289, International Conference on Intelligent Manufacturing and Industrial Automation (CIMIA 2022); 122890D (2022) https://doi.org/10.1117/12.2640856
Event: International Conference on Intelligent Manufacturing and Industrial Automation (CIMIA 2022), 2022, Kunming, China

Abstract

The connecting nut between phase B drain valve and gas tank of 51DK circuit breaker of high voltage shunt reactor of No. 1 bus in a substation was broken and failed. In order to find out the cause of fracture, the fractured brass connecting nut was comprehensively detected and analyzed by means of appearance morphology analysis, chemical composition analysis, microstructure detection and fracture micro area analysis. The results show that the chemical composition of brass nut is unqualified, the content of Cu element is low, and the content of Pb, Fe and impurity elements is high, which is easy to produce stress corrosion tendency, and the overheating structure is formed due to improper forging process, resulting in poor strength and toughness of the nut; Under the combined action of sulfide and stress, the stress corrosion cracking of externally threaded pipe occurs at the stress concentration part of the bottom of the first circle of thread, and gradually expands, so that the effective bearing area decreases, and finally breaks under the action of internal working pressure.

Citation Download Citation

Liming Xie, Feng Tian, and XinAi Guo "Cause analysis of cracking of brass connecting nut of circuit breaker", Proc. SPIE 12289, International Conference on Intelligent Manufacturing and Industrial Automation (CIMIA 2022), 122890D (24 October 2022); https://doi.org/10.1117/12.2640856

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