ANSI flange sealing principle

ANSI flange sealing principle is simple: two sealing surface compressive flange gasket bolt and form a seal. But it also causes the destruction of seal. In order to keep the seal, will have to maintain large bolt force. For this purpose, the bolt will be bigger. And a bigger bolt will match the bigger nut, which means the larger diameter bolts to create conditions to tighten the nut. Little imagine, the diameter of the bolt, the greater the applicable flange will become bent, the only way is to increase the flange part of the wall thickness. The whole device will requires a great deal of the size and weight, this in the offshore environment has become a special problem, because in this case the weight of people must concern has always been the main problem. And, ultimately, ANSI flange is an invalid seal, it requires a % of the bolt load for dummy blocks, and used to keep the pressure load only %.
however, ANSI flange of main design drawback is that it does not guarantee no leakage. This is insufficient on its design: the connection is dynamic, and such as thermal expansion and the ups and downs of cyclic load can create the flange surface between the moving, affect the function of the flange, to destroy the integrity of the flange is damaged, eventually lead to leakage.