Dependence of the seal property of ConFlat-type flanges on the fine dimensions of the knife edge

The shape of the sealing face on ConFlat-type flanges has not been addressed at all in the International Standards Organization standards, yet it is the distinct shape of the sealing face on the flange, generally referred to as the “knife edge” that primarily distinguishes the ConFlat sealing system. Results of profiling on the sealing face of 70 mm diameter ConFlat-type flanges, provided by ten individual manufacturers, reveal that while all the sealing faces share a common 20° angle on the taper face, there are variations in the tip radius of the knife edge, and in the angle of the counterslope against the 20° taper face. In flange tightening tests using the ConFlat flanges, the tip radius was observed to influence flange penetration into the gasket. It was also determined that the knife edges of all the test flanges were plastically deformed to some extent in the process of tightening twice at a torque of 120 kgf cm. The knife-edge shape was neither found to be dependent on the magnitude of deformation...