Conceptual Study on Maximum Allowable Lengthening for a 4629 DWT Tanker to Enhance Cargo Capacity and Convert to Dual-Fuel LNG/Diesel Propulsion

This study examines the midsection lengthening of a 4629 DWT tanker by adding proportional segments equivalent to the length of one tank. The still water bending moment of the original ship was estimated, and the combined bending moments for different scenarios in unrestricted waters were analyzed using MaxSurf. The original sectional modulus was calculated and compared using POSEIDON software, as well as the formulas provided by ABS and DNV for longitudinal strength assessment. To reduce CO₂ emissions, a dual-fuel propulsion system was proposed, taking advantage of the additional space made available by the lengthening. The EEXI of the original engine, the EEDI of the LNG-powered engine, and the CII were calculated, demonstrating notable emission reductions. As part of the optimization proposal, the tanker’s cargo capacity was increased, revealing the potential to boost revenue per voyage while simultaneously improving maritime routes through reduced emissions. Lastly, a structural and propulsion analysis of the lengthened vessel was performed using the Campbell diagram. The natural frequencies of the ship’s beam were estimated with POSEIDON, identifying critical zones and potential resonances that could impact structural integrity.