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All Journal Metalurgi Jurnal Polimesin
Ruskandi, Cecep
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Automotive Engineering Control & Systems Engineering Engineering Industrial & Manufacturing Engineering Materials Science & Nanotechnology Mechanical Engineering

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Investigation of Failure Mechanisms in the U-Bend Tubes of Shell and Tube Heat Exchangers Achyarsyah, Mochamad; Hanaldi, Kus; Purwadi, Wiwik; Hermana, Gita Novian; Siswanto, Ari; Ruskandi, Cecep; Nadi, Muhammad Rizki Gorbyandi
Metalurgi Vol 39, No 3 (2024): Metalurgi Vol. 39 No. 3 2024
Publisher : National Research and Innovation Agency (BRIN)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/metalurgi.2024.775

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.
Microstructural evolution and mechanical performance of Ni-modified sand-cast excavator bucket teeth Hidayat, Ery; Siswanto, Ari; Hermana, Gita Novian; Kusnowo, Roni; Ruskandi, Cecep; Gunara, Sophiadi; Komara, Asep Indra
Jurnal Polimesin Vol 24, No 2 (2026): April
Publisher : Politeknik Negeri Lhokseumawe

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.30811/jpl.v24i2.8744

Abstract

Excavator bucket teeth require high strength, hardness, and impact toughness to withstand severe service conditions involving abrasion and repeated impact. Achieving this combination of properties in sand-cast low-alloy steels remains challenging. This study investigates the microstructural evolution and mechanical properties of nickel-modified sand-cast bucket teeth subjected to a five-step heat treatment process. The material was produced by sand casting with the addition of 0.6 wt.% Ni, followed by sequential heat treatment consisting of normalizing, pre-tempering, quenching, and double tempering. Microstructural characterization and mechanical testing were conducted to evaluate the effects of the heat-treatment sequence on material performance. The applied heat treatment produced a lath martensite as the dominant microstructure with the presence of retained austenite. After the final tempering stage, the tensile strength reached 1206 MPa, with a hardness of 51 HRC, and an impact toughness of 26.1 J/mm2. The improved impact resistance is associated with retained austenite promoted by nickel addition. Fractographic analysis revealed predominantly ductile fracture characterized by dimple formation, followed by crack propagation involving intergranular and secondary cracking features. These results demonstrate that nickel modification combined with heat treatment effectively improves the mechanical performance of sand-cast bucket teeth.
Co-Authors Achyarsyah, Mochamad Ari Siswanto, Ari Asep Indra Komara Gita Novian Hermana Gunara, Sophiadi Hanaldi, Kus Hidayat, Ery Kusnowo, Roni Nadi, Muhammad Rizki Gorbyandi Purwadi, Wiwik