What is a flange?

Friends in forums and blogs often ask, what is a flange?
What is a flange?Most books say that flange, gaskets and fasteners are collectively called flanged joints.Flange joint is a kind of component widely used in engineering design.It is an essential part in piping design and fitting valve, and is also a common part in other engineering such as industry, thermal engineering, water supply and drainage, heating and ventilation, automatic control.

That may be standard, but fewer people understand it.For example, there is a long-distance transport pipeline, it must be a tube into the whole pipe, in this pipe but also installed on the valve, vision mirror, telescopic device, etc., this can be welding it up, but later maintenance can not be removed is not?So most of the pipeline will choose flange joint, in order to facilitate maintenance and replacement later.
One end of the flange is welded or otherwise connected to the pipe, and the two opposite flanges are fastened with fasteners (bolts) to form a complete pipe.Pipes and valves, eyeglasses, etc. are also connected in this way.