How does the flange connect to the steel pipe?
Flange type or structural type is the first flange and pipe connection method to distinguish,can be divided into: threaded flange,weld neck flange,plate flange, socket welding flange, loose flange,and blind flange.
The threaded flange is a kind of non-welded flange, in which the inner hole of the flange is machined into pipe thread and connected with the threaded pipe.Compared with the welded flange, the threaded flange has the characteristics of installation and repair convenience, which can be used in some pipelines where welding is not allowed.Alloy steel flange is not easy to weld, or welding function is not good, can choose threaded flange.
However, under the condition that the pipe temperature changes sharply or the temperature is higher than 260℃ or lower than -45℃, it is recommended not to use the threaded flange to prevent leakage.Butt welding flange, also known as high neck flange, it is different from other flange flange and pipe welding to flange has a long and askew high neck.
The wall thickness of this section of high neck gradually passes to the wall thickness of pipe along the direction of height, which improves the stress discontinuity and therefore increases the flange strength. Butt welding flanges are primarily used in severe working conditions.Such as: pipe thermal expansion or other load to make the flange of the stress is larger or stress change repeated occasions;The pressure, the temperature fluctuates greatly the pipeline or the high temperature, the high pressure and the low temperature condition application pipeline.
Plate flange is also known as lap welding flange.The connection between the plate flange and the pipe is to insert the pipe into the hole in the flange to the appropriate position first, and then welding, its advantage is easier to weld the installation, and the price is cheap, so it has been widely used. According to internal pressure accounting, the strength of the plate flange is about two-thirds of the corresponding welding flange, the number of fatigue life is about one-third of the welding flange.
Therefore, plate flange is only suitable for low pressure class, pressure shake, vibration are not severe in the pipeline system.plate flange can be subdivided into belt neck flat welding and plate flat welding two.
The basic shape of the socket welding flange is the same as that of the plate flange with neck. There is a section of the socket hole in the inner hole of the flange. The pipe is inserted into the socket and welded in the socket.Because there is a space between the flange and the pipe, it is sometimes prone to corrosion, which can be prevented by welding the seam inside.The fatigue strength of the socket welding flange is 50% larger than that of the plate flange, and the static strength is the same. When using this flange, the inside diameter should be the same as the inside diameter of the pipe.Socket welding flanges are only suitable for pipes with nominal diameter DN80 and below.