Stainless steel flange connections apply 573K temperature to the inner surface of the flange.  Flange and pipe surface without insulation layer.  The effects of bolt hole air layer, upper and lower flange air layer and flange surface heat transfer on the system temperature distribution are considered.  The main design defect of stainless steel flange is that it cannot guarantee no leakage.  This is where the design falls short.  

The connection is dynamic, such as thermal expansion and periodic load fluctuations will cause the movement between the flange faces, affect the function of the flange, thereby damaging the integrity of the flange, and eventually lead to leakage.