Flange, also known as a flange collar or rim, is a component used for connecting shafts to shafts, typically for pipe end connections; it is also used on equipment进出口 for connecting two devices, such as a reducer flange. A flange connection or flange joint refers to a detachable connection made up of a flange, a gasket, and bolts, forming a combination seal structure. Pipe flanges are the flanges used for piping in pipe systems; on equipment, they refer to the equipment's进出口 flanges. Flanges have holes and bolts are used to tightly secure the two flanges. They are sealed with a gasket. Flanges come in threaded (screwed) connections, welding flanges, and clamp flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while those above four kilograms of pressure use welding flanges. A sealant pad is placed between the two flange disks, and then bolts are used to secure them. Flanges of different pressures have different thicknesses and require different bolts. In the case of pumps and valves, when connected to pipes, the local parts of these equipment items are also made into corresponding flange shapes, also 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 the connection of ventilation pipes. These types of parts can be referred to as "flange-like 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-like part." Smaller items like valves can be called "flange-like parts."