What Is a Ring Flange?

A ring flange is a specialized pipe-joining flange that makes use of a compressible ring to ensure a secure seal. The ring may be made of a variety of materials, including various grades of rubber, fiber packings, and metals. When tensioned, the ring is located in a shallow groove cut into the face of flange plates. Prior to tensioning, the ring sits slightly proud of the plate faces and is compressed during tensioning of the joint to allow the flange faces to meet. Ring flange sets are available in a number of different designs, including various metal welded types and plastic loose and screw-on flanges.

Flanges are a popular method of joining pipes of various types and sizes in a wide range of industrial, agricultural, and domestic applications. Consisting of flat plates attached to the ends of two lengths of pipe, the flange joint is completed by drawing the two flange plates tightly against one another by means of bolts that pass through holes in either plate. The plates are secured to the ends of the pipe in several ways, including welding, epoxy, or threaded collars.

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.

When the flange joint is set up and ready for tensioning, the ring is placed in the groove on one of the faces and the joint is closed. As the ring is slightly bigger than the combined groove depth, it sits slightly proud of the flange plate faces. As the joint is tensioned, the ring compresses until the flange plates meet. This forms an extremely effective seal, greatly enhancing the efficacy of the joint as a whole.

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.