Flange, also known as a flange collar 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 connection consisting of a flange, a gasket, and bolts, forming a combined sealing structure. Pipe flanges are specifically used for piping in pipe installations, while on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts are used to tightly secure the two flanges together. Sealing pads are used between flanges for sealing. Flanges come in threaded (screwed) connections,焊接 (welded) flanges, and clamp flanges. Flanges are always used in pairs; low-pressure piping can use threaded flanges, while pressures above four kilograms require焊接 flanges. Two flange disks are joined with a sealing pad and then bolted together. Flange thickness and bolt types vary with pressure ratings. Equipment like pumps and valves, when connected to pipes, have corresponding flange shapes, also known as flange connections. Any connection piece that uses bolts to connect two flat surfaces and is sealed is generally called a "flange," such as in the case of ventilation pipe connections. These types of components can be referred to as "flange-type parts." However, such connections are only 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 components like valves can be referred to as "flange-type parts."