What are the factors that affect bolt flange sealing?

　　The bolted flange connection consists of a pair of flanges, several bolts, nuts, and a gasket. Tighten the bolts to compress the flange gasket and achieve sealing. However, the quality of flange sealing performance depends on many factors.

　　1. Pre tightening force of bolts

　　Pre tightening force is an important factor affecting sealing. Appropriate pre tightening force can ensure that the gasket can still maintain a certain sealing pressure during operation. If the pre tightening force is too large, the gasket will be crushed or squeezed out, thereby breaking the seal. The distribution of pre tightening force on the gasket also affects the sealing performance. The method to ensure uniform distribution of pre tightening force is to increase the number of bolts while meeting the space required for tightening and disassembling bolts.

　　2. Gasket sealing performance

　　Gaskets are important components for ensuring sealing. The appropriate gasket material can enable the gasket to produce necessary elastic deformation under appropriate pre tension without being crushed or extruded; Under the action of internal pressure during work, the bolt is stretched, causing the gap between the flange sealing surfaces to increase. At this time, the gasket material should have sufficient rebound ability to maintain close contact between the gasket surface and the flange surface, in order to continue to maintain good sealing performance; When selecting gasket materials, the working medium and working temperature should also be considered. The width of the gasket is also an important factor affecting the sealing. The wider the gasket, the greater the required pre tightening force, resulting in larger dimensions for bolts and flanges. But if the width of the gasket is too narrow, it may be crushed due to overload, resulting in connection failure.

　　3. Characteristics of flange sealing surface

　　The form and surface characteristics of the flange sealing surface play a crucial role in the sealing effect. In situations with high requirements, concave convex surfaces and mortise and tenon surfaces should be used. The flatness of the flange sealing surface and the perpendicularity between the sealing surface and the flange centerline directly affect the uniformity of the gasket's stress and the good contact between the gasket and the flange. The roughness of the flange sealing surface should match the requirements of the gasket, and there should be no radial knife marks or scratches on the surface, let alone surface cracks.

　　4. Flange stiffness and bolt stiffness

　　Insufficient stiffness can cause excessive warping and deformation of the flange, leading to seal failure. This is also the main reason for the failure of flange seals. There are many factors that affect flange stiffness, among which methods such as increasing flange thickness and increasing flange outer diameter can improve flange stiffness and reduce deformation. Reducing the distance between bolts can evenly transmit the bolt force to the gasket, obtaining a uniform and sufficient sealing pressure ratio, which can improve the sealing performance. The force arm that reduces the bolt force can reduce the bending moment borne by the flange, which is beneficial for sealing.

　　5. The impact of operating conditions

　　The operating temperature, pressure, and chemical and physical properties of the medium also affect the reliability of flange connections. As the temperature increases, the viscosity of the medium decreases, and the pressure increases, the driving force for medium leakage increases, and the tendency for leakage increases; High temperature increases the chemical and physical activity of the medium, leading to corrosion and dissolution of gaskets and flanges; High temperature can also cause creep and stress relaxation of bolts, flanges, and gaskets; Gas media, such as hydrogen, have a small molecular weight, which increases the likelihood of leakage.