Common flange structural types
1.Slip - on flange
Characteristics: The slip - on flange is a type of flange that is connected to the container and pipeline by fillet welds, also known as the lap - joint flange. When connecting the slip - on flange to the pipe, the pipe is first inserted into the inner hole of the flange to an appropriate position and then lap - welded. Its advantages lie in that it is relatively easy to align during welding and assembly, and it is inexpensive, so it has been widely used. The slip - on flange can be further divided into the neck - type slip - on and the plate - type slip - on.Applications: It is suitable for pipeline systems with relatively low pressure ratings, where pressure fluctuations, vibrations, and shocks are not severe. It is widely used in medium - and low - pressure pipeline connections.
2.Neck - type slip - on flange
Characteristics: The neck - type slip - on flange has a short neck. The design of this short neck enhances the strength of the flange and improves its load - bearing capacity, enabling it to be used on pipelines with higher pressures.
Applications: It has a wide range of nominal diameters and is suitable for various pipeline systems. Meanwhile, its nominal pressure range is relatively large, capable of meeting the requirements of different pressure ratings. It is widely used in pipeline systems of industries such as petroleum, chemical engineering, natural gas, metallurgy, food, and pharmaceuticals.
3.Welding neck flange
Characteristics: Also known as the long - neck flange, what sets it apart from other flanges is that there is a long and sloping high - neck section from the welding point of the flange and the pipe to the flange disc. The wall thickness of this high - neck section gradually transitions to the pipe wall thickness along the height direction, which improves the stress discontinuity and thus increases the strength of the flange.Welding neck flanges are mainly used in harsh working conditions. Welding neck flanges are large in size, heavy in weight and expensive in price. However, they feature a reasonable structure, high strength and stiffness, and can withstand high temperature, high pressure, repeated bending and temperature fluctuations.Applications: Due to their excellent performance, welding neck flanges are widely used in large - scale containers in fields such as aviation, petroleum and chemical industry. They are particularly suitable for pipelines with large pressure or temperature fluctuations, or pipelines under high - temperature, high - pressure or low - temperature conditions. They are also used in pipelines for transporting expensive, flammable, explosive and toxic gases.
4.Socket welding flange
Characteristics: The basic shape of the socket welding flange is the same as that of the neck - type slip - on flange. There is a socket in the inner hole of the flange. The pipe is inserted into the socket and welded, and a weld is made on the back of the flange.The fatigue strength of the socket welding flange welded on both the inner and outer sides is 50% higher than that of the slip - on flange. When using this kind of flange, its inner diameter should be the same as that of the pipe. The socket welding flange is only applicable to pipelines with a nominal diameter DN80 or less.
Applications: Socket welding flanges have small welding deformation and good sealing performance. They can be used in situations where the pressure ranges from 1.0 to 10.0 M Pa and are widely applied in industries such as boiler and pressure vessel, petroleum, and chemical engineering.
5.Threaded flange
Characteristics: The inner hole of the threaded flange is machined with pipe threads, which are connected to threaded pipes, making it a non - welded flange. Compared with welded flanges, threaded flanges are convenient for installation and maintenance.Applications: It is suitable for pipelines where on - site welding is not allowed, such as in industrial and civil pipe thread locking and sealing for fire - fighting, gas, cold and hot water systems. However, it is not recommended to use threaded flanges when the pipeline temperature changes sharply or when the temperature is higher than 260℃ or lower than - 45℃ to avoid leakage.
6.Integral flange
Characteristics: It refers to the flanges at the inlets and outlets of mechanical equipment such as pumps, valves, and machines, which are specifically used to connect with the flanges on pipes. The flange is usually cast integrally with the equipment.Applications: It is usually made as an integral part of the mechanical equipment and is regarded as a component of the equipment.
7.Blind flange
Characteristics: It has no hole in the center and is used to completely seal the end of a pipeline.Applications: It is used to isolate and block pipelines for equipment inspection, cleaning, replacement or other maintenance operations. It can be removed at any time, which is convenient for maintenance.
8.Loose flange
Characteristics: The flange can rotate, making it easy to align the bolt holes. When using this type of flange joint, the material of the flange accessories is the same as that of the pipe, while the flange material can be different from the pipe material.
Applications: It is easy to align the bolt holes and install on large - diameter pipelines. It is more suitable for pipelines transporting corrosive media and non - ferrous metal pipeline systems, aiming to save expensive materials as much as possible.
