The sealing principle of ANSI flanges is extremely simple: the two sealing surfaces of the bolt squeeze the flange gasket and form a seal. But this also leads to the destruction of the seal. To maintain the seal, a huge bolt force must be maintained. For this reason, the bolt must be made larger. Larger bolts must match larger nuts, which means that larger diameter bolts are needed to create conditions for tightening the nuts. As everyone knows, the larger the diameter of the bolt, the applicable flange will become bent. The only way is to increase the wall thickness of the flange part. The entire device will require a huge size and weight, which becomes a special problem in offshore environments because weight is always the main issue that people must pay attention to in this case. Moreover, fundamentally speaking, ANSI flanges are an ineffective seal. It requires 50% of the bolt load to be used for extruding the gasket, while only 50% of the load used to maintain pressure remains.

However, the main design disadvantage of ANSI flanges is that they cannot guarantee leak-free. This is the shortcoming of its design: the connection is dynamic, and cyclical loads such as thermal expansion and fluctuations will cause movement between the flange surfaces, affect the function of the flange, and damage the integrity of the flange, which will eventually lead to leakage.