Deterioration of seal reliability due to noncoaxial arrangement of ConFlat type flanges and gasket

Certain combinations of commercially available ConFlat type flanges with a gasket can yield an excessively wide gap between the gasket’s outer rim and the flange’s gasket-retaining counter. (The present ISO Technical Specification for the ConFlat type sealing system allows a maximum gap of some 0.8mm width.) Tightening this type of flange-and-gasket combination almost never results in a perfect coaxial arrangement; rather, it produces eccentric arrangements of the matching flanges and sandwiched gaskets. In a tightening test with coaxially arranged flanges and eccentrically arranged gaskets, seal performance was independent of the gap width, whether or not baking was included in the test conditions. The results indicate that the existing “capture model” lacks validity as a rationale for the seal mechanism of the ConFlat system. By contrast, the eccentric arrangement of matching flanges did prove to have a strong influence on seal reliability, particularly where the tightening test includes a baking proces...