LNG气化站低温管道设计方法

Design Method of Cryogenic Pipeline in LNG Gasification Station

因LNG管道的运行工况与安装工况间存在较大温差,需要采取补偿措施。以典型LNG气化站内低温管道为例,介绍主管、分支管及其支座的设计方法。低温管道的设计方法是先根据工艺流程初步确定管道及其支座,然后利用CAESARⅡV2014软件,对管道应力、位移、作用在支座上的力进行校核计算。为了保证支座不滑落,需综合考虑管道位移与支座选择,先根据管道位移初步选择支座,然后结合选定的支座校核管道位移。根据支座允许的管道位移,结合管道热胀冷缩情况计算出补偿区间。采用L形、Z形和方形补偿的LNG主干管,管道应力和作用在支座上的荷载均较小。管道柔性与自然补偿形式相关,Z形最好,L形居中,方形最差。对LNG分支管,结合应力计算结果,逐步增加弯头数量,直至主管三通和支管三通处的最大应力小于许用应力。设计了一种接气化器的凹形支管形式,应力计算结果合理。

Due to the large temperature difference between the the operating conditions and installation conditions of LNG pipeline,compensation measures need to be taken.Taking the cryogenic pipeline in a typical LNG gasification station as an example,the design methods of the trunk,branch and their supports are introduced.The design method of cryogenic pipeline is to initially determine the pipeline and its support according to the process flow,and then use the CAESAR II V2014 software to check and calculate the pipeline stress,displacement,and force acting on the support.In order to ensure that the support does not slip off,it is necessary to comprehensively consider the pipeline displacement and the support selection.Firstly,the support is initially selected according to the pipeline displacement,and then the pipeline displacement is checked in conjunction with the selected support.The compensation interval is calculated according to the allowable pipe displacement of the support,combined with the thermal expansion and cold contraction of the pipeline.Using L-shaped,Z-shaped and square-shaped compensation LNG trunk pipes,the pipeline stress and the load acting on the support are small.The flexibility of the pipeline is related to the natural compensation form.The Z-shape is the best,the L-shape is in the middle,and the square is the worst.For LNG branch,the number of elbows is gradually increased in combination with the results of stress calculations until the maximum stress at the main tee and branch tee is less than the allowable stress.A concave-shaped branch connected to the vaporizer is designed,and the stress calculation results are reasonable.