The reasons for flange leakage are as follows:
1. Deflection, refers to the pipe and flange are not vertical, different center, flange surface is not parallel. When the internal medium pressure exceeds the load pressure of the gasket, flange leakage will occur. This situation is mainly caused in the process of installation, construction or maintenance, and it is easier to be found. This kind of accident can be avoided only if it is checked properly when the project is completed.
2. Wrong mouth, refers to the pipe and flange are perpendicular, but the two flanges have different centers. The flange has different centers, so the bolts around it cannot penetrate the bolt holes freely. In the absence of other methods, only reaming or using a smaller size of the bolt through the bolt hole, and this method will reduce the tension of the two flanges. In addition, the sealing surface of the sealing surface line is also deviated, which is very easy to leak.
3. Open mouth, refers to the flange clearance is too large. When the clearance of the flange is too large and the external load is caused, such as axial or bending load, the gasket will be impacted or vibrated and lose the compression force, thus gradually losing the sealing kinetic energy and leading to failure.

4. Staggered hole means that the pipe and flange are concentric, but the distance between the bolt holes relative to the two flanges is large. The wrong hole will cause the bolt to produce stress, the force is not eliminated, will cause shear force on the bolt, the bolt will be cut off for a long time, resulting in sealing failure.
5. Stress influence, in the installation of the flange, the two flanges are more standard butt, but in the system production, after the pipeline into the medium, resulting in pipe temperature change, so that the pipeline expansion or deformation, so that the flange is subjected to bending load or shear force, easy to cause gasket failure.
6. Corrosion effect, because the corrosive medium on the gasket for a long time, so that the gasket chemical change. The corrosive medium penetrates into the gasket, and the gasket begins to soften and lose compression, resulting in flange leakage.
7. Thermal expansion and cold contraction. Due to the thermal expansion and cold contraction of the fluid medium, the bolts expand or contract, so that the gasket will produce a gap and the medium will leak through the pressure.