Flange, also known as a flange dish or boss, is a component used for connecting shafts or for joining pipe ends; it is also used on equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a detachable connection made up of a flange, gasket, and bolt, forming a combination seal structure. Pipe flanges are flanges used in piping installations; on equipment, they refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts are used to tightly connect the two flanges. The space between flanges is sealed with a gasket. Flanges are available in threaded (screwed) connections,焊接 (welded) flanges, and clamp flanges. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while pipelines over four kilograms of pressure require welding flanges. Two flange disks are placed with a sealing pad between them, then bolted together. Flanges of different pressures have varying thicknesses and require different bolts. When pumps and valves are connected to pipelines, the respective parts of these equipment are also shaped as flanges, known as flange connections. Any connection piece that uses bolts to connect two flat surfaces and is sealed simultaneously is generally called a "flange," such as in ventilation pipe connections, which can be referred to as "flange-like 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 "flange-like parts." Smaller components like valves can be referred to as "flange-like parts."