Flange, also known as a flange disc or boss, is a component used for connecting shafts to each other or for joining pipe ends. It is also used on equipment进出口 for connecting two devices, such as reducer flanges. Flange connection or flange joint refers to a detachable connection consisting of a flange, a gasket, and bolts, forming a combined sealing structure. Pipe flanges are those used in piping installations, and on equipment, they refer to the equipment's进出口 flanges. Flanges have holes for bolts to securely connect two flanges, which are sealed with a gasket. Flanges come in threaded (screwed) connections, welding connections, and clamp connections. Flanges are used in pairs; low-pressure piping can use threaded flanges, while pressures over four kilograms require welding flanges. Two flange disks are joined with a sealing gasket and then bolted together. Flanges of different pressures have varying thicknesses and require different bolts. Equipment like pumps and valves, when connected to pipes, have locally shaped flanges corresponding to these connections, also known as flange joints. Any connection piece that uses bolts to connect two flat surfaces around the perimeter and is sealed is generally called a "flange," such as in ventilation pipe connections. These types of components can be referred to as "flange-type parts." However, such connections are only a part of a device, like the connection between a flange and a pump, so it's not appropriate to call the pump a "flange-type part." Smaller equipment like valves can be called "flange-type parts."