A Pipe Flange can be defined as an external or internal rib, or rim, for strength (as the flange of an iron beam) or for a guide (as the flange of a train wheel) or for attachment to another object (as the flange on the end of a pipe, steam cylinder, etc). It allows two pipes to be mechanically connected together, or a pipe to be mechanically connected to a valve, tee, choke or other piece of equipment. Hence, it is a connection profile that is used in pipe work and associated equipment to provide a means of assembling and disassembling components.

The design and specification of a flange relates to the size and pressure capacity of the equipment to which it is fitted. All flanges are sized according to their nominal bore size. For the majority of pipe sizes, this designation does not represent either their actual outside diameter or inside diameter.

Working of a Pipe Flange :
The basic principle of working is to use a mechanical force (exerted by the bolts) to pre-load the gasket so that when internal pressure (end cap force) is applied, there is enough contact stress between the flanges and gasket to maintain a seal. The flange itself needs to be connected to the pipe. This is usually achieved by welding, though threaded and other weldless connections also exist.

Flange can be made of various materials like :