Stress Analysis of LNG Storage Tank Outlet Pipes and Flanges

Abstract

The liquefied natural gas (LNG) tank outlet pipe is the weak part of any LNG vaporizing station. Due to the ultralow temperature characteristics of LNG, pipeline damage or leakage may cause major accidents. This paper used the finite element analysis method and the CAESAR II software to analyze the stresses of LNG storage tank outlet pipes and flanges in a LNG vaporizing station, the influencing factors (compensator type, compensator position, LNG density, pressure, temperature) are analyzed, and stress reduction measures are discussed. According to the results of the analysis, the following main conclusions can be obtained: (1) the most dangerous working condition of the LNG storage tank outlet pipe is the precooling condition; under this condition, the comprehensive stress, displacement and support force are the largest; (2) compared with the Z-type and L-type compensators, the effect of the π-type compensator to reduce the stress of the low temperature pipe is the best; (3) when the length of the cold tightening unit is 40% of the cold shrinkage, the stress reduction effect is the best.

Keywords

• liquefied natural gas (LNG) storage tank
• stress analysis
• outlet pipe
• flange
• stress reduction measure