Combination flange gasket seal joint is the main sealing element, which is connected by means of bolts through the flange bolt holes in the bolt preload force of the sealing surface of the flange clamping force is applied to the flange stuffing live uneven sealing surface between the micro-geometry of the gap to achieve the purpose of sealing. As tightening flange sealing joints and working conditions (pressure) conditions are established by the initial sealing gasket sealing force and the work force as a prerequisite, since from the viewpoint of the design of the flange, the connection method should be connected throughout the bolt and the seal gasket interconnected together for an overall consideration, the most important consideration is the gasket.