﻿ 船用LNG储罐与管道应力计算
 舰船科学技术  2018, Vol. 40 Issue (1): 35-40 PDF

1. 武汉理工大学 能源与动力工程学院，湖北武汉 430063;
2. 中国船级社 武汉规范研究所，湖北武汉 430020

Marine LNG tank and pipeline stress calculation
GAN Shao-jing1, ZHOU Rui-ping1, GAN Shao-wei2, SU Yang1
1. School of Energy and Power Engineering, Wuhan University of Technology, Wuhan 430063, China;
2. Wuhan Rules and Research Institute, China Classification Society, Wuhan 430020, China
Abstract: For the specific characteristics of LNG, marine LNG tank and pipelines have to meet certain requirements for strength. Therefore, the strength calculation on the tank and pipelines is indispensable. The outer tank wall connects to the pipelines directly. Hence, its deformation at the pipeline connections has a great impact on the value and distribution of the pipeline stress. With the aid of FEM, this paper completed the modeling analysis of marine LNG tank and pipeline respectively, as well as twice stress check on the pipeline, taking the deformation at the pipeline connections as displacement loading. Finally, the stress analysis method on marine LNG tank and pipelines has been explored, which will provide the theoretical basis for the designs of tank and pipelines.
Key words: marine LNG tanks     pipelines     stress calculation
0 引 言

1 研究对象及工具 1.1 研究对象

 图 1 LNG储罐和管道系统示图 Fig. 1 LNG storage tank and piping system diagram

 图 2 低温液货管系示图 Fig. 2 Cryogenic liquid cargo piping diagram
1.2 研究工具

 图 3 应力计算流程图 Fig. 3 Stress calculation flow chart
2 应力分析理论

2.1 储罐应力分析

2.2 管道应力分析

2.2.1 一次应力

ASME B31.3[10]规定的纵向应力为一次应力。管道纵向应力值的计算，因按照ASME B31.3中所规定，考虑轴向力的作用。因此，一次应力由附加轴向外力、管道内压和弯矩引起，即

 ${\sigma _1} = \frac{F}{{{A_m}}} + \frac{{P{D_0}}}{{4\delta }} + \frac{{{M_T}}}{Z}{\text{。}}$ (1)

 ${\sigma _1} \leqslant \left[ {{\sigma _h}} \right]{\text{。}}$ (2)

2.2.2 二次应力

 ${\sigma _2} = \frac{{\sqrt {{i_i}{M_i}{^2} + {i_0}{M_0}{^2} + 4{M_t}^2} }}{Z}{\text{。}}$ (3)

 $\left\{ \begin{array}{l}{\left[ \sigma \right]_A} = f\left[ {1.25{\sigma _c} + 0.25{\sigma _h}} \right], \\{\sigma _2} \leqslant {\left[ \sigma \right]_A}{\text{。}}\end{array} \right.$ (4)

3 储罐结构强度校核 3.1 储罐有限元建立

 图 4 储罐三维模型示图 Fig. 4 Three-dimensional model of tank

 图 5 储罐有限元模型示图 Fig. 5 Tank finite element model diagram
3.2 储罐载荷及约束

 图 6 前冲2 g工况载荷及约束示图 Fig. 6 Load and constraint diagram of 2 g working condition
3.3 储罐强度与结果

4 管系应力计算 4.1 LNG管道计算参数

4.2 出液管系模型

 图 7 低温液货管道模型轴测图 Fig. 7 Cylindrical map of cryogenic cargo pipeline model
4.3 约束条件与载荷工况

1）储罐和低温潜液泵池接口处约束。储罐外部管道接口通过管帽与外罐体焊接固定，LNG储罐的变形将作为管道入口处位移载荷；管道与和循环水气化器、冷箱及低温潜液泵池之间设置为固定端（全约束）。

2）管道支撑处的约束。船用LNG管路中的支架一般用导向性约束模拟，即放开管道轴向自由度，约束其他方向自由度，与船体相连的管道支架直接简化为导向约束。

5 管系计算结果分析

 图 8 下冲2 g管系一次应力整体分布图示 Fig. 8 Downward 2 g pipe stress distribution of the overall distribution diagram

 图 9 前冲2 g管系二次应力整体分布图示 Fig. 9 2 g forward pipe system of the overall distribution of secondary stress

6 结 语

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