Flange, also known as a flange disk or rim, is a component used to connect shafts to each other or to pipe ends for connection purposes; it's 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 removable connection made up of the flange, gasket, and bolts working together as a combined sealing structure. Pipe flanges are specifically used for piping in equipment installations, referring to the equipment's inlet and outlet flanges. Flanges have holes for bolts to tightly secure them together, and they are sealed with a gasket. Flanges come in threaded (screwed) connections,焊接 connections, and clamp connections. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while those over 4 kg of pressure require焊接 connections. Two flange disks are joined with a sealing pad and then bolted together. Flange thickness varies with pressure, and so do the bolts used. Pumps and valves, when connected to pipelines, have locally shaped flanges that correspond to these devices, also known as flange connections. Any connection piece that uses bolts to connect and seal two flat surfaces around the periphery is generally called a "flange," such as in the connection of ventilation pipes. Such components can be referred to as "flange-type parts." However, this type of connection is only a part of a single device, like a flange connected to a pump, so it's not appropriate to call the pump a "flange-type part." Smaller devices like valves can be called "flange-type parts."