Session: 

Submission Number: 158414

Fatigue Analysis and Rapid Prediction of Inner Corrugated Pipe in LNG Flexible Hose 

Liquefied natural gas (LNG) flexible hoses are core components in offshore LNG transfer operations. They are subjected to marine loads that can induce multi-axial fatigue damage in inner corrugated pipes. To address this challenge, a fatigue analysis method of inner corrugated pipes is proposed based on multi-axial fatigue theory. Furthermore, to accelerate the fatigue analysis process, an RBF neural network is employed to develop a surrogate model that establishes relationship between design parameters and fatigue life. Case study results demonstrate the accuracy and time-saving advantages of the surrogate model in predicting fatigue life. These findings offer a valuable reference for the fatigue analysis of LNG flexible hose.

INTRODUCTION

Natural gas is a clean and environmentally friendly high-energy fuel. In recent years, China's natural gas consumption has rapidly increased, creating an urgent need for breakthroughs in key technologies for its transportation and transmission. The transfer of liquefied natural gas (LNG) from LNG carriers to the shore-based terminal is a critical link in the LNG import transportation chain. Traditional LNG receiving terminals require specialized docks for loading and unloading operations, consisting mainly of the receiving berth, unloading arms, storage tanks, control systems, and safety systems. Upon arrival at the terminal, the LNG carrier must dock at a designated berth, where LNG is safely transferred to the shore-based storage tanks via unloading arms. However, the construction of traditional receiving LNG terminals is time-consuming and costly, and the site selection is constrained by factors such as water and land conditions, navigation safety, and other considerations.

To address these challenges, the jettyless floating system, as shown in Fig. 1, is emerging and gradually being promoted. In this system, when the LNG carrier arrives at the terminal, a transfer platform drags LNG flexible hoses to connect with the LNG carrier, then performs the LNG transfer operation (Yang et al., 2022). The typical LNG flexible hose is illustrated in Fig. 2. The innermost layer of this hose, the inner corrugated pipe, is typically made of austenitic stainless steel and is the only metal layer (Zhang et al., 2010), exhibiting excellent flexibility under cryogenic conditions. During LNG transfer operations, LNG flexible hoses are subjected to marine random loads, which can lead to fatigue damage in inner corrugated pipes. Therefore, fatigue analysis of the inner corrugated pipes is crucial for structural integrity of LNG flexible hoses and ensuring the safe operation.

Presenting Author: Kailun Zhang CNOOC Research Institute Ltd.

Presenting Author Biography: Zhang Kailun, offshore pipeline structure engineer at CNOOC Research Institute Ltd., completed his Master's degree in Engineering Mechanics at Dalian University of Technology. His research primarily focuses on hydrodynamic analysis, fatigue analysis, multi-objective optimization, and experimental validation of LNG flexible hoses and flexible risers