1. Bolt pretightening force

Proper pretightening force can ensure that the gasket can retain a certain seal pressure when working, but too much pretightening force will crush or extrude the gasket, thus destroying the seal.The distribution of pretightening force on the gasket also affects the sealing performance. The method to ensure the uniform distribution of pretightening force is to increase the number of bolts under the condition of meeting the space required for tightening and removing bolts.

2.gasket sealing performance

Gasket is an important component of seal.Suitable gasket material should reflect that the gasket can not only produce the necessary elastic deformation under the action of appropriate pre-tightening force, but also not be crushed or extruded.When working, the distance between the flange sealing surface is extended, and the gasket material should have enough rebound ability, so that the gasket surface and the flange surface close contact, in order to continue to maintain good sealing performance.

3. Characteristics of flange sealing surface

The type and surface performance of flange sealing surface play an important role in sealing effect.Concave and convex surface and tenon groove surface should be used when working conditions are more strict.The flatness of flange sealing face, the center line and verticality of sealing face and flange directly affect the stress uniformity of gasket and the good contact between gasket and flange.The surface roughness of the sealing surface of the flange should be adapted to the requirements of the gasket, and the surface is not allowed to have radial marks or scratches, let alone surface cracks.

4. Flange stiffness

Insufficient stiffness will lead to excessive warping of the flange, resulting in seal failure.There are many factors affecting the flange stiffness, among which increasing the flange thickness, increasing the flange diameter and other methods can improve the flange stiffness, reduce the deformation, make the bolt force evenly transferred to the gasket, obtain uniform and enough specific sealing pressure, and improve the sealing performance.Reduce bolt force action of the moment arm, can reduce the flange bearing moment, is conducive to sealing.

5. Operating conditions

Pressure vessel flange operating temperature, pressure and chemical and physical properties of medium also affect the reliability of flange connection.As the temperature increases, the medium viscosity decreases and the leakage tendency increases.High temperature increases the chemical and physical activity of the medium, resulting in corrosion and dissolution of gaskets and flanges.High temperature can also cause creep and stress relaxation of the ladyplugs, flanges and gaskets.