FPSO串靠外输时的碰撞性能分析

FPSO与穿梭油轮进行串靠外输过程中,穿梭油轮首部可能与FPSO尾部发生碰撞事故,称为“尾碰”。目前的相关研究主要集中在碰撞过程中的风险分析,缺少对FPSO“尾碰”事故碰撞性能的合理分析与评估。本文针对某15万吨级FPSO,基于动态非线性有限元分析软件ABAQUS,采用同步损伤分析技术,研究了串靠外输过程中FPSO与穿梭油轮之间由于过分纵荡运动而引起的碰撞事故。通过数值仿真计算,分析了包括“尾碰”后结构的损伤变形、应力应变关系、碰撞力和吸能情况的船舶碰撞内部动力学,进而对FPSO尾部结构的碰撞性能进行评估。结果表明,FPSO尾部结构中板材结构吸收的能量约占尾部结构总吸能的75.5%,其吸能能力显著优于T型骨材结构,研究结果对FPSO尾部结构的耐撞性设计具有一定的参考意义。

Collision Analysis for FPSO in Tandem Offloading Operation

As a comprehensive large marine oil production base,FPSO has become the main production mode of marine oil and gas resources development.The oil and gas of FPSO are generally transported by shuttle tankers in the form of tandem offloading operation which is able to adapt to complex operation conditions in sea conditions and has higher safety.According to the experience of the shuttle tankers’company,excessive surging is one of the most dangerous factors that affect the safety of the offloading operation.And the extreme excessive surging may cause collision accident.In tandem offloading operation,that FPSO’s stern is impacted by shuttle tanker’s bow is a possible but critical accident called stern collision.Stern collision accidents often cause damage to FPSO’s stern structure and a large number of oil spills,resulting in marine environmental pollution,personnel casualties,loss of property,and other serious consequences.At present,there is no reasonable analysis and assessment on crashworthiness for stern collision,while relevant specification mainly pays attentions on risk analysis of collision.Therefore,this paper focuses on the collision accident during tandem offloading operation due to the extreme excessive surging.In order to improve the crashworthiness of the FPSO’s stern structure and ensure its safety during tandem offloading operation,it is of great significance to analyze and evaluate stern collision performance at the design stage.This paper focuses on simulating the collision accident due to excessive surging between 150000 t FPSO and 100000 t tandem offloading shuttle tanker.In this paper,the internal mechanics of ship collisions is mainly studied.The dynamic structural response and energy absorption of the hull structure are analyzed.Then the effect of the flow field around the hull is simplified as the additional water mass,while the motion between the hulls is ignored.The collision scenario is selected according to the FPSO tandem offloading operation mode.The numerical simulation is carried out by the dynamic non-linear finite element analysis software ABAQUS based on synchronized damage analysis.The crashworthiness of FPSO’s stern structure is checked and evaluated by analyzing the damage deformation,stress-strain relationship,collision force,and energy absorption.In addition,the energy absorbing abilities of each component in FPSO’s stern structure are compared.From the study in this paper,we got some conclusions.(1)Ahuge depression similar to the shape of the bulbous bow appears at the stern transom plate of FPSO.Compared with the degree of damage deformation in FPSO’s stern structures,the degree of damage deformation in shuttle tanker’s bow structures is smaller because of larger relative structural stiffness.Although FPSO’s stern structures absorb most of the impact energy,shuttle tanker’s bow structuresabsorb part of the impact energy,which accounts for about 39%of the total energy absorption.(2)The center line bulkhead,the stern transom plate and the bottom plate of the FPSO’s stern area are the main energy absorbing components.(3)The energy absorbed by panel structures is up to 75.5%in the total energy absorption of FPSO’s stern structure,while the other 24.5%is absorbed by T-beams.Finally,the results may have some reference significance to the structural crashworthy design for FPSO’s stern structure.