The two sealing faces of the flange bolt press each other against the flange gasket and form a seal, but this also causes damage to the seal. In order to maintain the seal, you have to maintain a huge bolt force. Bolts have to be bigger
Larger bolts will match larger nuts, which means that larger diameter bolts are needed to create conditions for tightening nuts. The larger the diameter of the bolt, the more suitable the flange will become. The only way is to increase the wall thickness of the flange. The entire installation will require a great size and weight, which becomes a special problem in the offshore environment because weight is always a major concern for people in this situation. Fundamentally, the ANSI flange is an ineffective seal that requires 50% of the bolt load to be used to squeeze the gasket, while the load used to maintain the pressure is only 50%.
The main design disadvantage of ANSI flanges is that it does not guarantee leak-free. The connection is dynamic, and cyclic loads such as thermal expansion and undulation can cause movement between the flange faces, affecting the function of the flange, thereby impairing the integrity of the flange and ultimately leading to leakage.