The edge-loaded metal flange seal—its characteristics and applications

Abstract

An edge-loaded metal ring flange seal has been developed for ultrahigh bakeable vacuum operation that requires closing forces comparable to elastomeric seal systems. Sealing is accomplished using a deformable rectangular cross-sectioned copper ring confined between stainless steel flanges in a manner that produces high radial compressive forces upon alternate edges of the ring section during flange closure. Conformation to the geometry and macrostructure of the confining elements of the flanges produces a leak-tight seal capable of ultrahigh vacuum operation with 400 °C bakeout. The seal ring deformation has been analyzed and the seal configuration has been tested for reliability and loading characteristics and found to require axial forces as low as 45 pounds per circumferential inch of seal for the system. A simplified analysis has been developed to predict loading characteristics and has been compared to loading studies made during the development of the seal system. Tests in ambient and elevated temperature environments show the seal to be as reliable as existing ultrahigh vacuum seal systems while requiring as little as 1/40 the bolt forces and 1/10 the time to accomplish closure. The flange seal has utility in radiation induced environments where human exposure time may be severely restricted, or where remote handling techniques for flange assembly and disassembly may be required.