Prefabricated pipeline flanges are connected to pipes by means of pipes

　　Prefabricated pipes for gas transportation flange can be divided into five basic types according to the connection mode with pipe:plate flange, welded neck flange, threaded flange (integral flange), slip on flange, loose sleeve flange.

　　1. plate flange: suitable for carbon steel pipe connection with nominal pressure not exceeding 2.5MPa. The sealing surface of flat welding flange can be made into three kinds: smooth, concave convex and tenon groove. Smooth flat welded flange is the most widely used flange. It is mostly used under mild medium conditions, such as low-pressure non-purified compressed air and low-pressure circulating water. Its advantage is that it is cheaper.

　　2. welded neck flange: used for welded neck flange and pipe for prefabricated pipes, its structure is reasonable, strength and stiffness larger, withstand high temperature and pressure, repeated bending and temperature fluctuations, reliable sealing.

　　3. threaded flange: commonly used in PN less than 10.0MPa, DN less than 40 of the prefabricated pipes.

　　4. Loose-sleeve flange: Loose-sleeve flange commonly known as looper flange, welding ring looper flange, flanging looper flange and butt welding looper flange. Commonly used in medium temperature and pressure are not high and medium corrosive. When the medium is corrosive, the part of the flange contact medium (flanging knuckle) is high-grade corrosion-resistant material such as stainless steel and other materials, while the external use of low-grade materials such as carbon steel flange ring clamping it to achieve sealing.

　　5. Integral flange: often flange and equipment, pipes, fittings, valves, etc. into one, this type is commonly used in prefabricated pipes.