Flange, also known as a flange disk or rim, is a component used for connecting shafts or for joining pipe ends. It is also used at equipment inlets and outlets, such as reducer flanges, for connecting two pieces of equipment. A flange connection or flange joint refers to a removable joint that consists of a flange, a gasket, and bolts, forming a combined sealing structure. Pipe flanges are flanges used for piping in pipeline installations, and on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts secure them tightly together. They are sealed with a gasket. Flanges come in threaded (screwed) connections, welded flanges, and clamp flanges. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while those above four kilograms of pressure use welded flanges. Two flange disks are joined with a sealing pad and then fastened with bolts. Flanges of different pressures have different thicknesses and require different bolts. Pumps and valves, when connected to pipelines, have locally shaped flanges corresponding to these equipment pieces, also known as flange connections. Any connection piece that uses bolts to connect two flat surfaces around the perimeter and is sealed is generally called a "flange," such as the connection of ventilation pipes. These types of parts can be referred to as "flange-type parts." However, such connections are only a part of a single device, like the connection between a flange and a pump, so it's not appropriate to call the pump a "flange-type part." Smaller items like valves can be called "flange-type parts."