Due to the load and deformation of the flange joint involves complicated factors, can only be used for a long time experience and flange stress calculation to reflect indirectly, foreign codes have been included in the flange stiffness calculation method, and the container is to ensure the safe operation of the pressure vessel standards and regulations as the goal, pressure vessel safety become the pronoun of preventing failure or brittle fracture strength.The sealing mechanism of the flange joint produces a certain sealing force between the gasket and the sealing surface of the two flanges after the bolt is tightened. At this time, the sealing force on the unit area of the gasket is called the pre-tightening specific pressure. The pre-tightening specific pressure causes the gasket to produce a certain deformation, so as to ensure the sealing of the contact surface.

The material of flange gasket is different, and the requirement of preload ratio is different.When the medium pressure rises, the pressing force of the gasket is reduced compared with the preloading state due to the effect of the internal pressure.After the bolt is tightened, a certain sealing force is produced between the gasket and the sealing surface of the two flanges.