A flange is an external or internal ridge between two pipes that provides a method of connecting pipes, valves, pumps and other equipment to form an overall piping system.

In many applications, engineers need to find a way to close off a chamber or cylinder in a very secure fashion, usually because the substance inside must differ from the substance outside in composition or pressure. They do this by fastening two pieces of metal or other material together with a circle of bolts on a lip. This “lip” is a flange.

Flanges can also provide easy access for cleaning, inspection or modification and pipes with flanges can be assembled and disassembled easily. Flanges tend to be either welded or screwed into place.