A flange, also known as a flange disc or flange ring, is a component used to connect shafts to one another or to join pipe ends. Flanges are also used at the inlets and outlets of equipment to connect two pieces of equipment, such as in the case of a reducer flange. A flange connection, or flange joint, refers to a removable connection consisting of a flange, a gasket, and bolts that work together to form a sealed assembly. Pipe flanges refer to flanges used for piping in piping systems, while those used on equipment refer to the inlet and outlet flanges of the equipment. Flanges have bolt holes, and bolts are used to tightly connect two flanges. A gasket is used to seal the space between the flanges. Flanges are classified into threaded flanges, welded flanges, and clamp flanges. Flanges are always used in pairs; threaded flanges can be used for low-pressure piping, while welded flanges are used for pressures above 4 kg/cm². A gasket is placed between two flange discs, which are then secured with bolts. Flanges of different pressures have varying thicknesses and require different types of bolts. When connecting pumps and valves to pipelines, the corresponding parts of these devices are also designed with flange shapes, which is also referred to as a flange connection.