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Email this article Investigation of Failure Mechanisms in the U-Bend Tubes of Shell and Tube Heat Exchangers
Abstract
The U-bend tubes of a shell-and-tube heat exchanger made of SA-234 Grade WPB carbon steel failed prematurely within 14 days after replacement and welding. This study investigates failure mechanisms through an integrated failure analysis that includes visual inspection, dye penetrant testing, chemical composition analysis, hardness measurements, and microstructural characterization. The results reveal that the tube contained 0.324 wt.% C, exceeding the maximum limit specified by the standard, which promoted the formation of Widmanstätten ferrite and reduced toughness. The welded joint exhibited multiple defects, including porosity and lack of fusion, which acted as stress concentration sites. Hardness measurements showed average values of 205 HV in the weld metal, 199 HV in the HAZ (heat-affected zone), and 184 HV in the base metal. Under operating conditions of 275 °C and 58.48 barg, these defects progressively opened, leading to fluid leakage. The escaping high-pressure fluid accelerated erosion-corrosion, as evidenced by oxygen-rich corrosion products detected by EDS analysis. The findings demonstrate that the combined effects of material non-compliance, poor welding quality, and unfavorable microstructural evolution governed the premature failure. This study provides quantitative insights to improve welding practices and material selection, thereby enhancing the reliability of U-bend tubes in shell-and-tube heat exchangers.
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C. Wu, H. Yang, X. He, C. Hu, L. Yang, and H. Li, "Principle, development, application design and prospect of fluidized bed heat exchange technology: Comprehensive review," Renewable and Sustainable Energy Reviews, vol. 157, p. 112023, 2022.
E. Purnomo, A. Wiranata, and M. A. Muflikhun, "Microstructural and Mechanical Characterization of U-Bend Economizer Failures: Integrating Experimental Testing and CFD Simulation," Journal of Materials Research and Technology, 2025.
C. R. d. F. Azevedo, F. B. Neto, S. D. Brandi, and A. P. Tschiptschin, "Cracking of 2.25 Cr–1.0 Mo steel tube/stationary tube-sheet weldment of a heat-exchanger," Engineering Failure Analysis, vol. 15, no. 6, pp. 695-710, 2008.
L. Liu, N. Ding, J. Shi, N. Xu, W. Guo, and C.-M. L. Wu, "Failure analysis of tube-to-tubesheet welded joints in a shell-tube heat exchanger," Case Studies in Engineering Failure Analysis, vol. 7, pp. 32-40, 2016.
R. T. Mousavian, E. Hajjari, D. Ghasemi, M. K. Manesh, and K. Ranjbar, "Failure analysis of a shell and tube oil cooler," Engineering Failure Analysis, vol. 18, no. 1, pp. 202-211, 2011.
H. Panahi, A. Eslami, M. Golozar, and A. A. Laleh, "An investigation on corrosion failure of a shell-and-tube heat exchanger in a natural gas treating plant," Engineering Failure Analysis, vol. 118, p. 104918, 2020.
S. Xu, C. Wang, and W. Wang, "Failure analysis of stress corrosion cracking in heat exchanger tubes during start-up operation," Engineering Failure Analysis, vol. 51, pp. 1-8, 2015.
Z. G. Yang, Y. Gong, and J. Z. Yuan, "Failure analysis of leakage on titanium tubes within heat exchangers in a nuclear power plant. Part I: Electrochemical corrosion," Materials and Corrosion, vol. 63, no. 1, pp. 7-17, 2012.
M. Rezaei, Z. Mahidashti, S. Eftekhari, and E. Abdi, "A corrosion failure analysis of heat exchanger tubes operating in petrochemical refinery," Engineering Failure Analysis, vol. 119, p. 105011, 2021.
V. Korobko, A. Shevtsov, S. Serbin, H. Wen, and M. Dzida, "Impact of the type of heat exchanger on the characteristics of low-temperature thermoacoustic heat engines," International Journal of Thermofluids, vol. 24, p. 100953, 2024.
F. Yan, H. Lu, and S. Feng, "Numerical Simulation of Liquified Natural Gas Boiling Heat Transfer Characteristics in Helically Coiled Tube-in-Tube Heat Exchangers," Frontiers in Heat and Mass Transfer, vol. 22, no. 5, pp. 1493-1514, 2024.
D. Abson, "Acicular ferrite and bainite in C–Mn and low-alloy steel arc weld metals," Science and Technology of Welding and Joining, vol. 23, no. 8, pp. 635-648, 2018.
A. Takada, H. Terasaki, and Y. Komizo, "Effect of aluminium content on acicular ferrite formation in low carbon steel weld metals," Science and Technology of Welding and Joining, vol. 18, no. 2, pp. 91-97, 2013.
S. S. Babu, "The mechanism of acicular ferrite in weld deposits," Current opinion in solid state and materials science, vol. 8, no. 3-4, pp. 267-278, 2004.
M. Amraei et al., "Mechanical properties and microstructural evaluation of the heat-affected zone in ultra-high strength steels," Thin-Walled Structures, vol. 157, p. 107072, 2020.
A. Smith, M. Asadikiya, M. Yang, J. Chen, and Y. Zhong, "An investigation of creep resistance in grade 91 steel through computational thermodynamics," Engineering, vol. 6, no. 6, pp. 644-652, 2020.
S. Afkhami et al., "Thermomechanical simulation of the heat-affected zones in welded ultra-high strength steels: Microstructure and mechanical properties," Materials & Design, vol. 213, p. 110336, 2022.
H. Zhou, Q. Zhang, B. Yi, and J. Wang, "Hardness prediction based on microstructure evolution and residual stress evaluation during high tensile thick plate butt welding," International Journal of Naval Architecture and Ocean Engineering, vol. 12, pp. 146-156, 2020.
C. Capdevila, F. G. Caballero, C. García-Mateo, and C. G. De Andrés, "The role of inclusions and austenite grain size on intragranular nucleation of ferrite in medium carbon microalloyed steels," Materials transactions, vol. 45, no. 8, pp. 2678-2685, 2004.
M.-Y. Chen, H.-W. Yen, and J.-R. Yang, "The transition from interphase-precipitated carbides to fibrous carbides in a vanadium-containing medium-carbon steel," Scripta Materialia, vol. 68, no. 11, pp. 829-832, 2013.
Y. Chi, Y. Tsai, B. Huang, and J. Yang, "Investigation of idiomorphic ferrite and allotriomorphic ferrite using electron backscatter diffraction technique," Materials Science and Technology, vol. 33, no. 5, pp. 537-545, 2017.
T. Yokomizo, M. Enomoto, O. Umezawa, G. Spanos, and R. Rosenberg, "Three-dimensional distribution, morphology, and nucleation site of intragranular ferrite formed in association with inclusions," Materials Science and Engineering: A, vol. 344, no. 1-2, pp. 261-267, 2003.
C. Capdevila, F. Caballero, and C. García de Andrés, "Modeling of kinetics of austenite-to-allotriomorphic ferrite transformation in 0.37 C-1.45 Mn-0.11 V microalloyed steel," Metallurgical and Materials Transactions A, vol. 32, pp. 661-669, 2001.
W. Lange, M. Enomoto, and H. Aaronson, "The kinetics of ferrite nucleation at austenite grain boundaries in Fe-C alloys," Metallurgical Transactions A, vol. 19, pp. 427-440, 1988.
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