Evaluation of Sealing Performance of Pipe Flange Connections for Low Temperature Fluids by Numerical Analysis

Recently, low temperature fluids are used more commonly, and consequently, leakage related accidents become crucial issues. These accidents are mainly due to significant shrinkage of pipe flange connection elements. It has been reported that leakage accidents often occur when low temperature fluids start to flow, or when the flow rate starts to decrease. This is because under these circumstances, the clamping force in bolts connecting a pair of pipe flanges is presumed to decrease significantly. In the previous paper, a numerical approach based on Finite Element method (FEM) was proposed to simulate a simpler flow condition than those in actual pipelines. In this paper, the numerical approach is applied to more realistic conditions by enabling the surface of low temperature fluids to move up and down. When using liquid nitrogen, the bolt force was reduced to less than 40% of its initial value shortly after the fluid started to flow. When applying the numerical method to an LNG pipeline, it was found that the bolt force momentarily showed a significant reduction as was the case with liquid nitrogen.