Evaluation of Thermal and Mechanical Behaviors of Pipe Flange Connections for Low Temperature Fluids by Numerical Analysis and Experiments

Abstract

Sealing of contained fluids is the primary criteria required for pipe flange connections. Recently, there is a rapid rate of increase in the use of low temperature fluids, and leakage related accidents are sometimes reported. The leakage mechanism seems to be different from the case in pipe flange connections at elevated temperatures. In this paper, it is examined experimentally how the leakage of low temperature fluids occurs, in which a pipe flange connection is cooled by liquid nitrogen. The variations of bolt temperature and bolt force are continuously measured. Experimental results show that the bolt force is reduced to as low as about 65% of the initial value. Next, a numerical method based on three-dimensional FEM is proposed to simulate the cooling process. Numerical results are in good agreement with those obtained by experiments. Applying the numerical method to the pipe flange connections for LNG, it is found that the bolt force reduces to about 70% of the initial value. The numerical method proposed in this paper is expectantly applied to the cases of different low temperature fluids under various flow conditions.