page_title: Piping and plumbing fitting
section_title: Flange fittings
hierarchical_section_title: Piping and plumbing fitting / Connection methods / Flange fittings
context_page_description: A fitting or adapter is used in pipe systems to connect straight sections of pipe or tube, adapt to different sizes or shapes, and for other purposes such as regulating fluid flow. These fittings are used in plumbing to manipulate the conveyance of water, gas, or liquid waste in domestic or commercial environments, within a system of pipes or tubes.
  Fittings require money, time, materials and tools to install, and are an important part of piping and plumbing systems. Valves are technically fittings, but are usually discussed separately.
context_section_description: Flange fittings are generally used for connections to valves, inline instruments or equipment nozzles. Two surfaces are joined tightly together with threaded bolts, wedges, clamps, or other means of applying high compressive force. Although a gasket, packing, or O-ring may be installed between the flanges to prevent leakage, it is sometimes possible to use only a special grease or nothing at all (if the mating surfaces are sufficiently precisely formed). Although flange fittings are bulky, they perform well in demanding applications such as large water supply networks and hydroelectric systems. 
  Flanges are rated at 150, 300, 400, 600, 900, 1500 and 2500 lbs or 10, 15, 25, 40, 64, 100 and 150 bars of pressure. Various types of flanges are available, depending on construction. Flanges used in piping (orifice, threaded, slip-on, blind, weld neck, socket, lap-joint, and reducing) are available with a variety of facings, such as raised, flat, and ring-joint.
  Slip-on flanges are slipped over the pipe and welded to provide strength and prevent leakage. This flange is less expensive than a weld neck and requires less accuracy when cutting pipe to length. Blind flanges are used to shut off a piping system or opening, while still allowing easy access for inspection.
  A weld neck flange is joined to a piping system by butt welding. Although its long neck (or hub) makes it expensive, it reduces mechanical stress on piping by distributing stress between the base of the flange and the wall at the weld. Turbulence and erosion are reduced due to the matching size of the pipe and flange.
  A socket flange appears similar to a slip-on flange, but its bore is counter-bored to accept pipe. A fillet weld around the hub of the flange attaches the flange to the pipe, with an interval weld added in high-stress applications. It is most frequently used in high-pressure systems, such as hydraulic and steam lines.
  A lap-joint flange is similar to a slip-on, with room at the intersection of the bore and the flange face for a lap stub end. The face of the stub end conforms to the gasket face of the flange. It is used where sections of piping need to be dismantled quickly and easily for inspection or replacement.
caption: Flange connection with a gasket