Armored steel wire stress monitoring strategy of a flexible hose in LNG tandem offloading operation

Abstract

Cryogenic flexible hose is the key equipment for tandem offloading operation of Floating Liquefied Natural Gas (FLNG). The harsh marine environment leads hulls motion responses and complex hose motion characteristics during the tandem offloading, thus causing various failure behaviors of the entire hose. In this paper, a combined global-local monitoring strategy for armored steel wire stress distributions in cryogenic flexible hose is proposed. High-precision flexible hose governing equations are established by using the function to fit the relationship between the vertical force and the hose length. A reasonable monitoring strategy is given based on the pipeline configuration variations and sensor accuracy. Real-time monitoring of the flexible hose from the global (hose) to the local (armored steel wire) during the tandem offloading is carried out by installing sensors in specified locations on hulls and hose segments. The tandem offloading operation under different (static, calm and harsh) sea states is modelled by Orcaflex software. An armored steel wire model is developed using ABAQUS software. Comparisons of the pipeline configurations, curvatures, axial forces and maximum wire stresses are made with the simulation results to verify the feasibility of the monitoring strategy. The results show that the proposed monitoring strategy in this paper can accurately and effectively obtain the hose motion characteristics and maximum stress states of armored steel wires under different sea states, and can evaluate the hose structural safety in real time during the tandem offloading operation.