A flange is a mechanism by which pipes, valves, pumps, and other equipment are connected to form a piping system. It also offers easy accessibility for cleaning testing or modification purposes. Flanges are normally welded or screwed. The flanged connections are made by bolting together two flanges with a gasket to provide a seal.
Often known as screwed flanges, threaded flanges have a thread inside the flange bore that fits into the pipe with matching male thread on the pipe. This type of joint connection is fast and easy but not suitable for high pressure and temperature applications. Threaded flanges are used mostly in facilities such as air and water services.
Socket-Weld Flanges has a female socket in which the pipe is installed. Fillet welding is done from the outside of the pipe. It is generally used in small bore pipes and is only suitable for low pressure and temperature application.
Slip-On flange has a hole with the corresponding external diameter of the pipe from which the pipe can pass. The flange is placed on the pipe and then fillet welded both in and out. Slip-On Flange is appropriate for low pressure and temperature applications. This type of flange is also available in large sizes to connect large-bore pipes to storage tank nozzles. Usually, these flanges are of forged construction and are fitted with a hub. Sometimes these flanges are made from plates and do not come with a hub.
Lap Joint Flanges
The lap flange has two components, a stub end, and a loose back flange. Stub end is butt-welded to the pipe, and the back flange moves freely over the pipe. The backing flange can be made of a material other than stub material and, generally, of carbon steel to save costs. Lap flange is used where repeated disassembly is required and space is limited.
Weld Neck Flanges
Weld neck flange is the most commonly used type of process pipes. This provides the highest level of joint integrity as a consequence of the Butt-welded pipe. Such types of flanges are used in the application of high pressure and temperature. Weld neck flanges are heavy and costly with respect to other types of flanges.
The blind flange is a blank disc with a bolt hole. These types of flanges are used with another type of flange to separate the pipe system or to terminate the pipe as an end. Blind flanges are also used in the vessel as a manhole cover.