Study of the flange gasket leakage path under fretting wear
GUO Yanbao , ZHANG Zheng , WANG Deguo , HE Renyang
1 College of Mechanical and Transportation Engineering, China University of Petroleum-Beijing, Beijing 102249, China 2 China Special Equipment Inspection and Research Institute, Beijing 100029, China
Today, station and pipeline transportation are the most important methods in various energy engineering fields, especially in the oil and gas industry. In the natural gas gathering and transmission system, the gas station has a vital role, and its reliability can affect the safety of the entire pipeline system to a large extent. Due to the diversity of equipment and instruments the bolt-gasket flange connection is the main mode of connection in the gas station. It is well recognized that the gasket is thecore sealing element which is critical to the safety performance of the whole pipeline system. In the process of natural gas transportation, pressure pulsations generated in the gas will inevitably cause the pipeline to vibrate a little, and act on the sealing interface of the flange and gasket in the form of fretting wear, thus reducing the tightnessand sealing performance of the bolt-gasket-flange connection. Through the fretting wear test of common spiral wound gaskets(SWG), the influence of fretting wear on the interface between SWG and flange seals on the connection was observed andanalyzed, and the "star" type gasket micro-leakage path unit was established according to the size effect of wear scars. FLUENTsoftware was used to conduct numerical simulation of the fluid characteristics inside the micro-leakage path unit generated by fretting wear. We explored the variation of the leakage process under different pipeline pressures and leakage modes, and analyzed the areas vulnerable to high-pressure erosion of the internal channel wall through the stress shear cloud diagram of the flexible graphite wall.The results show that the leakage modes (number of leakage ports) has a big impact on the distribution of the flow field and velocity in the leakage path unit. The inlet velocity of the first level leakage mode is high, but the diffusion ability is relativeweak. The outlet velocity of the third level leakage mode reaches the maximum. Also, the temperature does not directly affect the change of the internal flow field. The volume flow rate of the channel inlet/outlet interface of the micro-leakage path unit increases with an increase of pressure. Moreover, the erosion region of the shear force on the flexible graphite wall varies with the leakage modes. Compared with the other two leakage modes, the first level leakage mode presents greater wall shear stress. The maximum shear stress of the third level leakage mode occurs in the middle region, and has a greater influence on theerosion of the graphite wall surface. Eventually, the leakage path model under fretting wear can finally provide references for theestablishment and optimization of a flange gasket leakage model and evaluation system to a certain extent.
GUO Yanbao, ZHANG Zheng, WANG Deguo, HE Renyang. Study of the flange gasket leakage path under fretting wear. Petroleum Science Bulletin, 2020, 03: 420-428.
