Leakage control for a flat flange model with a gap based on sealing liquid viscosity

Abstract

Flat flanges are sealed using a gasket, used to prevent leakage between the static surfaces. Gaskets comprise synthetic materials such as rubber, copper alloys, and plastic and they are inserted between two planes to strengthen the sealing performance. Leakage is circumvented by the elastic and plastic deformation of materials. However, it can be difficult to reduce leakage because of the rough nature and waviness of the solid surface; moreover, excessive clamping force may lead to surface damage. Leakage is directly proportional to the cube of the gap height and inversely proportional to lubricant viscosity. Viscosity is strongly dependent on temperature; the lower the temperature, the higher the viscosity. Thus, it is possible to control the leakage by changing the temperature of sealing parts to enhance the sealing performance of gaskets. In this paper, a flange-type gasket system with a gap is modeled using two circular plates with a central recess. Using a prototype, the effects of plate temperature, recess pressure, gap height, plate parallelism, sealing width, oil viscosity grade, and the vibration frequency and amplitude are experimentally examined under steady-state and harmonic vibration conditions. In parallel, the thermo-hydrodynamic lubrication (THL) and iso-viscous (IV) theories are applied to the gap flow and theoretical simulation was conducted. The theoretical results based on THL and IV theories agreed with the experimental data for a wide range of conditions including controlled temperature, viscosity grade, effective sealing size, inclined angle, and vibration parameters. Accordingly, this study shows that leakage can be decreased by cooling the sealing parts of gasket for all the included parameters under static and vibration conditions.