The part that connects the pipe to the pipe, connected to the pipe end. There are holes on the flanges, and bolts make the two flanges tightly connected. The flanges are sealed with gaskets. Flanged pipe fittings (flanged pipe fittings) refer to pipe fittings with flanges (flanges or flanges). It can be cast (not shown in the figure), or it can be threaded or welded. Flange connection (flange, joint) consists of a pair of flanges, a gasket and several bolts and nuts. The gasket is placed between the sealing surfaces of the two flanges. After the nut is tightened, the specific pressure on the surface of the gasket will deform when it reaches a certain value, and fill the unevenness on the sealing surface to make the connection tight and leak-proof. Flange connection is a detachable connection. According to the connected components, it can be divided into container flange and pipe flange. According to the structure type, there are integral flanges, looper flanges and threaded flanges. Common integral flanges include flat welding flanges and butt welding flanges. Flat welding flanges have poor rigidity and are suitable for occasions where the pressure is p≤4MPa; butt welding flanges, also known as high neck flanges, have higher rigidity and are suitable for occasions with high pressure and temperature. There are three types of flange sealing surfaces: flat sealing surface, suitable for occasions where the pressure is not high and the medium is non-toxic; concave-convex sealing surface, suitable for occasions with slightly higher pressure; tongue and groove sealing surface, suitable for flammable and explosive , toxic media and occasions with high pressure. A gasket is a ring made of a material that can produce plastic deformation and has a certain strength. Most of the gaskets are cut from non-metallic plates, or made by professional factories according to the specified size, and their materials are asbestos rubber sheets, asbestos sheets, polyethylene sheets, etc.; Metal clad gaskets made of non-metallic materials such as wrapping; there is also a spiral wound gasket made of thin steel strips and asbestos strips. Ordinary rubber gaskets are suitable for occasions where the temperature is lower than 120 °C; asbestos rubber gaskets are suitable for occasions where the temperature of water vapor is lower than 450 °C, the temperature of oil is lower than 350 °C, and the pressure is lower than 5MPa. The most commonly used medium is acid-resistant asbestos board. In high-pressure equipment and pipelines, lens-type or other-shaped metal gaskets made of copper, aluminum, 10-gauge steel, and stainless steel are used. The contact width between the high-pressure gasket and the sealing surface is very narrow (line contact), and the processing finish of the sealing surface and the gasket is high. Flange is divided into threaded connection (wire connection) flange and welding flange. The low-pressure small diameter has a wire flange, and the high-pressure and low-pressure large diameter use welded flanges. The thickness of the flanges and the diameter and number of connecting bolts are different for different pressures.