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All Journal International Journal of Marine Engineering Innovation and Research Eduvest - Journal of Universal Studies
Winarto
Universitas Indonesia
Aerospace Engineering Automotive Engineering Computer Science & IT Control & Systems Engineering Decision Sciences, Operations Research & Management Electrical & Electronics Engineering Energy Engineering Environmental Science Health Professions Industrial & Manufacturing Engineering Materials Science & Nanotechnology Mechanical Engineering Neuroscience Physics Social Sciences Transportation

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Crack Analysis Due to Fatigue Load During Subsea Pipeline Installation Franciscus Ventus Nagoya; Winarto
International Journal of Marine Engineering Innovation and Research Vol. 7 No. 3 (2022)
Publisher : Department of Marine Engineering, Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25481479.v7i3.5604

Abstract

Most of the subsea pipelines in Indonesia are installed using the S-Lay method with the pipelay barges equipped with mooring spreads, tensioners, and stinger. During the subsea pipeline installation, static loads occur due to the pipeline configuration from the firing line of the pipelay barge up to the seabed. The pipe will experience axial tension and bending moment in two critical areas: overbend and sagbend. In addition, fatigue loads occur during subsea pipeline installation due to environmental loads (i.e., currents and waves). Defects that are found after welding will grow due to these fatigue loads. Crack analysis with a fracture mechanic approach known as Engineering Critical Assessment (ECA) is carried out by considering the fatigue load due to significant wave height variations for 0.5m, 1.0m, and 1.8m. BS 7910 is used as a standard reference to determine the allowable defects criteria for external and internal flaws. The depth of the defect (a) is simulated from a depth of 1mm – 3mm. The analysis found that the allowable defect length is decreased by 12.7% - 25.0% from a significant wave height of 0.5m to 1.8m for the external surface flaw. While for an internal surface flaw, the allowable defect length is decreased by 5.9% - 13.6% from a significant wave height of 0.5m to 1.8m. These results can be used as a basis for subsea pipeline installation contractors to perform fatigue load sensitivity and optimize the allowable defects based on the actual wave load at the site.
Spheroidization and Its Effect on the Decrease in Mechanical Strength of Steel SA210 Gr. A1 Titis Aditya; Winarto
Eduvest - Journal of Universal Studies Vol. 6 No. 5 (2026): Eduvest - Journal of Universal Studies
Publisher : Green Publisher Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.59188/eduvest.v6i5.52677

Abstract

SA210 Gr. A1 is an important material used in piping systems and boiler components due to its high mechanical strength and resistance to high temperatures. However, long-term exposure to high temperatures can cause microstructural degradation through the spheroidization process, which results in a decrease in mechanical properties. This study aims to evaluate the effect of the spheroidization process on the mechanical strength and microstructure of SA210 steel Gr. A1. The methods used include spheroidization heat treatment at 660°C with time variations of 3, 10, and 100 hours, followed by Vickers hardness testing and tensile testing per ISO 6892-1. After 100 hours of spheroidization, ultimate tensile strength (UTS) decreased from ~51.5 to ~43.9 kgf/mm² (15% reduction), yield strength (YS) decreased from ~44.7 to ~28.4 kgf/mm² (36% reduction), and Vickers hardness decreased from ~169 to ~141 VHN (17% reduction). Elongation increased from 28% to 47% (68% increase), indicating significantly improved ductility at the cost of strength. Results show that spheroidization contributes to a decrease in tensile strength (UTS) and yield strength (YS), but increases the ductility (elongation) value and decreases the hardness of the material. This transformation makes the material more ductile, but at the cost of reduced mechanical durability.
Co-Authors Franciscus Ventus Nagoya Titis Aditya