독립형 LNG 화물창의 공학적 결함 평가
Engineering Critical Assessement for an Independent Type-B LNG Cargo Tank
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초록
The demand for Liquefied Natural Gas (LNG) carriers and LNG-fueled ships has significantly increased in recent years due to the sulfur-oxide emission regulations by the International Maritime Organization (IMO). The main goal of this paper is to introduce the process for the Engineering Critical Assessment (ECA) of IMO independent type-B cargo tanks made from 9% nickel alloy. A methodology proposed by the British Standard was used to conduct ECA for any structure with initial flaws. Based on this standard, a Matlab code was developed to perform ECA. Coarse mesh Finite Element Analysis (FEA) was performed on an independent type-B LNG cargo tank with a capacity of 15,000 m3. The location with the highest development of maximum principal stress was identified at the bottom of the cargo tank. Fine mesh FEA was performed to obtain the stress range required for ECA. The dynamic cargo tank loads used for FEA were determined using some ship rules presented by Det Norske Veritas. As a result of performing a 20-year long-term crack propagation analysis with a semi-elliptical surface crack, the fracture-to-yield ratio exceeded the Fracture Assessment Line (FAL) and some structural reinforcement was necessary. Performing a 15-day short-term crack propagation analysis, the fracture-to-yield ratio remained within the FAL, and no significant LNG leaks were expected. This paper is believed to provide a guide for performing ECA of LNG cargo tanks in the future by providing the basic theory and application sample necessary to perform ECA.
Abstract
The demand for Liquefied Natural Gas (LNG) carriers and LNG-fueled ships has significantly increased in recent years due to the sulfur-oxide emission regulations by the International Maritime Organization (IMO). The main goal of this paper is to introduce the process for the Engineering Critical Assessment (ECA) of IMO independent type-B cargo tanks made from 9% nickel alloy. A methodology proposed by the British Standard was used to conduct ECA for any structure with initial flaws. Based on this standard, a Matlab code was developed to perform ECA. Coarse mesh Finite Element Analysis (FEA) was performed on an independent type-B LNG cargo tank with a capacity of 15,000 m3. The location with the highest development of maximum principal stress was identified at the bottom of the cargo tank. Fine mesh FEA was performed to obtain the stress range required for ECA. The dynamic cargo tank loads used for FEA were determined using some ship rules presented by Det Norske Veritas. As a result of performing a 20-year long-term crack propagation analysis with a semi-elliptical surface crack, the fracture-to-yield ratio exceeded the Fracture Assessment Line (FAL) and some structural reinforcement was necessary. Performing a 15-day short-term crack propagation analysis, the fracture-to-yield ratio remained within the FAL, and no significant LNG leaks were expected. This paper is believed to provide a guide for performing ECA of LNG cargo tanks in the future by providing the basic theory and application sample necessary to perform ECA.
참고문헌 (13)
- British Standards Institution, ". Guide to methods for assessing the acceptability of flaws in metallic structures: British standard BS 7910:2019, Fourth edition" (2019), British Standards Institution
- Liquefied gas carriers with independent prismatic tanks of type A and B, "DNVGL", ~ (2017)
- Rules for classification Ships Part 3Chapter 4 Loads, "DNVGL", ~ (2017)
- Dowling, N. E., "Mechanical behavior of materials: engineering methods for deformation, fracture, and fatigue, Fifth edition, global edition" (2020), Pearson, Harlow
- 강범준, "ECA 기법을 이용한 해양구조물의 결함 평가", 대한조선학회 논문집, 52(6), pp.435~443 (2015), 대한조선학회
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- 이진성, "An experimental study on fatigue performance of cryogenic metallic materials for IMO type B tank", International Journal of Naval Architecture and Ocean Engineering, 5(4), pp.580~597 (2013), 대한조선학회
- 이원구, "Reliability Improvement of Offshore Structural Steel F690 Using Surface Crack Nondamaging Technology", 한국해양공학회지, 35(5), pp.327~335 (2021), 한국해양공학회[DOI]
- International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code), "Maritime Safety Committee (MSC)", International Maritime Organization, ~ (2016)
- 박은영, "Greenhouse Gas Emission Analysis by LNG Fuel Tank Size through Life Cycle", 한국해양공학회지, 35(6), pp.393~402 (2021), 한국해양공학회[DOI]
- 송하철, "Assessment of Cryogenic Material Properties of R-PUF Used in the CCS of an LNG Carrier", 한국해양공학회지, 36(4), pp.217~231 (2022), 한국해양공학회[DOI]