The ring flange
is a special flange type that includes an extra sealing element sandwiched between the two plate faces. A shallow groove is machined into the flange plate faces, typically towards the center of the plate below the row of tensioning holes. These flanges usually come in sets that include a separate sealing ring of the same dimensions as the groove. These rings may be made of rubber compounds, fiber, or soft steel, and are round or square in cross section. They are also of a slightly larger diameter than the combined depths of the two grooves.
Most flange types including metal and plastic weld, epoxy, or threaded types are available as ring flange sets of various sizes. The integrity of the ring flange makes it ideal for aggressive environments featuring high pressures. These characteristics see large numbers of ring flanges used in installations such as petroleum refinement, natural gas, and chemical processing plants.