The two sealing faces of the bolt are pressed with each other to form a seal, but at the same time, it also leads to the destruction of the seal. In order to keep the seal, you have to maintain a huge bolt force, to this end, the bolt will do even greater. A bigger bolt nut must match the larger, which means that the larger diameter bolts need to create conditions for the tightening nut. However, the greater the diameter of the bolt, the flange will become more curved, the only way is to increase the thickness of the flange part of the flange. The whole device will require a great deal of size and weight, which is a special issue in the offshore environment, because in this case the weight is always the main problem that people have to pay attention to. Fundamentally, Weld Neck Flange is an invalid seal, it needs to take 50% of the bolt load for gasket extrusion, while maintaining pressure on the load for only 50%.