Common reasons for flange leakage:

1. Misalignment: Misalignment refers to the situation where the pipe and flange are not aligned straight, causing the surrounding bolts to not fit easily into the bolt holes due to the two flanges being off-center. Some may choose to use oversized holes or smaller bolts, but this will reduce the clamping force of the flange.
 
2. Offset: Offset means that the pipe and flange are not in a vertical position, and the flange faces are not parallel and off-center. If the internal medium pressure exceeds the load pressure of the gasket, leakage will occur.
 
3. Corrosion: Long-term corrosion of the gasket by corrosive media can cause chemical changes in the gasket, making it soft and losing its clamping force.
 
4. Misdrilled holes: Misdrilled holes are relatively easy to understand, where the pipe and flange are concentric, but the distance between the corresponding bolt holes of the two flanges is too large, causing stress on the bolts. Over time, this can lead to the bolts breaking, resulting in seal failure.