Flange, also known as a flange disc or raised rim. A flange is a component used for connecting shafts to each other and for joining pipe ends; there are also flanges used at equipment inlets and outlets, such as reducer flanges, for connecting two pieces of equipment. A flange joint or flange connection refers to a detachable joint consisting of a flange, a gasket, and bolts, forming a combined sealing structure. Pipe flanges refer to flanges used for piping in pipeline installations, while those on equipment refer to the equipment's inlet and outlet flanges. Flanges have holes, and bolts secure them together. They are sealed with a gasket. Flanges are available in threaded (screwed) connections, welding flanges, and clamping flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while those over four kilograms of pressure require welding flanges. Two flange discs are fitted with a sealing pad and then bolted together. Flanges of different pressures have varying thicknesses and require different bolts. Pumps and valves, when connected to pipes, have locally shaped flanges to match, also known as flange connections. Any connection piece used to join two flat surfaces around the perimeter with bolts and simultaneously seal them is generally called a "flange," such as in the case of ventilation pipe connections, these components can be referred to as "flange-type components." However, this type of connection is only a part of a single device, such as the connection between a flange and a pump, so it's not appropriate to call the pump a "flange-type component." Smaller items like valves can be referred to as "flange-type components."