دانلود رایگان مقاله تحلیل شکست لوله به صفحه لوله در مبدل حرارتی پوسته و لوله

ABSTRACT

Failure analysis was carried out on a tube-to-tubesheet welded joint of a shell-tube heat exchanger to confirm its failure mechanism. The collected evidence suggests that the failure of the tube-to-tubesheet welded joint was induced by fatigue. Under the morphology analysis, the fracture surface exhibit obvious fatigue crack propagation traces. Fatigue striations were observed clearly in the propagation zone. Detecting results showed that chemical composition and mechanical properties of the tubes was consistent with the standard requirements for the 304 stainless steel. The metallographic test showed that the microstructure of both the tube and tubesheet were normal. However, serious defects were found at the tube-to-tubesheet welded joint. The fatigue crack initiated from the defects at the tube-to-tubesheet welded joint. The periodic load might come from the resonant vibration of the tube or the changes in temperature and pressure of the fluid inside the heat exchanger. Bad welding and unsuitable expansion position of the tubes at the tube-to-tubesheet might give rise to the formation of initial cracks.

5. Conclusions

In summary, the collected evidence suggests that the failure mechanism of the tube-to-tubesheet in the shell-tube heat exchanger was fatigue fracture. The fracture surfaces showed obvious crack propagation traces. Fatigue striations, which were the micro-evidence of fatigue, were observed clearly. The fatigue crack initiated from the defects at the tube-totubesheet welded joint. The periodic load might come from the resonant vibration of the tube or the changes in temperature and pressure of the fluid inside the heat exchanger. Bad welding and unsuitable expansion position of the tubes at the tubeto-tubesheet might give rise to the formation of initial cracks. In future, prevention of failure of the shell-tube heat exchanger would still be an important topic. Improving the quality of welding and expansion processes were effective way to reduce the failure problems of the tube-to-tubesheet welded joint in such heat exchangers.