LNG储罐气相管结构的改进

利用有限元法分析计算了某LNG储罐气相管装料及卸料时的热应力，发现最大应力在气相管与内容器连接部位，其与气相管实际断裂位置吻合。分析结果表明：虽然装料与卸料会导致一定的压力与温度循环，但造成的交变应力强度幅很小，可以忽略其引起的疲劳损伤。造成结构破坏的原因为过大热应力导致的结构安定性失效。当内容器轴向收缩受限时，气相管应具有足够大的柔性，才能有效降低热应力，满足结构的安定性要求。从约束及热变形补偿入手，对消除及缓解LNG储罐气相管热应力的措施进行了探讨。（图5，参6）

Improvement of gas-phase pipe structure for LNG tank

The thermal stress of gas-phase pipe for a LNG tank is analyzed and calculated when loading and unloading materials with finite element method. Results indicate that the maximum stress is at the joint between the gas pipe and inner container, which is consistent with actual rupture location of gas-phase pipe. The results show that although loading and unloading would cause a certain amount of pressure and temperature cycling, the range of alternating stress intensity is very small, and the fatigue damage by which is ignored. The reason for structural damage is the structural stability failure due to high thermal stress. When the axial contraction of inner container is limited, the gas pipe should have sufficient flexibility, only in this way, can thermal stresses be effectively reduced to meet the stability requirements of the structure. Starting from the constraints and thermal deformation compensation, the measures to eliminate and mitigate the heat stress of gaspipe of LNG storage tank are discussed. （5 Figures, 6 References）