Flange, also known as a flange hub or rim. A flange is a component used for connecting pipes to each other or for connecting equipment at inlets and outlets, such as reducer flanges. Flange connection or flange joint refers to a detachable connection consisting of the flange, gasket, and bolts connected together as a set of combined sealing structure. Pipe flange refers to the flange used for piping in a pipeline system, or the inlets and outlets of equipment. Flanges have holes, and bolts are used to tightly connect the two flanges. Gaskets are used to seal between flanges. Flanges are divided into threaded connection (screwed connection) flanges, welding flanges, and clamp flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while pipelines above 4 kg pressure use welding flanges.