Metal & Oil & Gas News – Nctv.net
Flange is a common part in piping system. They are mainly used to connect shafts and shafts or to connect two devices. In general, flanges are used with gaskets and bolts. The purpose is to fix two pipes, pipe fittings or equipment on the flange, then add flange gasket between the two flanges, and then use bolts to tighten the two flanges to make it tight connection. Therefore, it is also a common connection method in pipeline system.
However, we will find that the flange connection will still fail in the actual production process. This may be caused by three factors of flange, gasket and bolt, such as insufficient flange stiffness, bolt stiffness and bolt pre tightening stiffness, form and surface characteristics of flange sealing surface and selection of gasket (and sealing performance), or incorrect flange installation and use. It may also be affected by operating temperature, pressure and the chemical and physical properties of the medium. Therefore, we need to select the flange, gasket and bolt first, and then install them. This is to make better use of the sealing performance of flange connection. So, can we touch the flange directly during the flange installation? What are the precautions for flange installation?
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Ensure that the sealing surface is clean and free from defects
Before installing the flange, we need to make sure that the sealing surface of the flange is clean and free from defects. The sealing surface of flange should be cleaned. This is because the sealing surface of flange should be closely connected with washer and bolt. If the flange sealing surface is not cleaned, flange leakage is likely to occur in the future use process, and the proper sealing performance of the flange will be invalid. As for the defect free flange sealing surface, it means that the flange sealing surface has no defects such as radial scratch, serious corrosion and deformation.
When cleaning the flange sealing surface, use latex gloves, alcohol, dust-free cloth and other tools. We need to wear latex gloves, moisten the dust-free cloth with alcohol, and then wipe the whole flange. It is worth noting that when cleaning the flange sealing surface, do not use a screwdriver to clean it, so as not to damage the flange sealing surface.
Flange installation
Connection between flange and pipe
The connection of flange and piping system requires high connection skills, because not only the strength of the connection part, but also the tightness should be considered during installation. If one of the two points fails to meet the standard, the pipeline may be damaged. Therefore, flange and pipe installation should meet the following requirements:
- (1) The center of the flange must be in line with the center of the pipe.
- (2) The flange sealing surface must be perpendicular to the piping center.
- (3) The position of flange threaded hole on the pipeline shall be consistent with that on the opposite equipment or pipeline, and the position of flange threaded hole on both ends of the same pipeline shall be consistent.
Installation of flat welding flange
The installation process of flat welding flange is relatively simple. When installing, the flange should be put into the pipe end first, and then a certain distance should be left between the pipe orifice and the flange sealing surface, which is determined by the pipe wall thickness. Then you can start spot welding on both sides of the pipe.
Installation of weld neck flange
Weld neck flange this kind of pipe fittings refers to the flange with neck and round pipe transition and butt welding connection with the pipe. Different from flat welding flange, weld neck flange is not easy to deform and has good sealing performance. In addition, they are relatively cheap, so they are widely used. Weld neck flange is suitable for pipes with large fluctuation of pressure or temperature or high temperature, high pressure and low temperature pipes. It is used to transport precious, flammable and explosive media. So, do you know how to install and use weld neck flange? When installing and using weld neck flange, we should know the precautions?
- 1. Before installing the weld neck flange, pay attention to check whether the nominal pressure of the flange meets the design requirements; check whether the sealing surface of the flange is smooth and clean, whether there are burrs and radial grooves, and whether the threaded part of the flange is complete and intact. Whether the concave and convex flange can fit in naturally, especially the nondestructive testing of the welding flange must be done well, so as to avoid damaging the inside of the welding flange and affecting the performance and service life of the flange.
- 2. Please pay attention to cleaning before installing weld neck flange. After all, the sealing surface of the flange should be tightly connected with washer and bolt. Flange sealing surface shall be cleaned with special cleaning tools and methods to prevent damage of weld neck flange.
The installation and use of weld neck flange must pay attention to the method and sequence. After all, if the installation method and installation sequence is wrong, it will affect the flange installation, so that the flange can not be installed. In the process of use, due to the influence of transportation medium and operating conditions, loosening and sliding may also occur, which will lead to pipeline leakage. Therefore, in order to use the weld neck flange better and longer in the future, we need to master the correct installation method and installation sequence of the welding flange.
There are two installation methods for welding flange:
- 1. Before connecting the weld neck flange, first arrange the inside and outside of the stainless steel pipe fittings, and then install the flange with slotted ring on the pipe to be connected. Above, the end of the pipe needs 90 degree flanging. After treatment, the end surface of the pipe needs to be polished. After grinding, it should be free of burr, concave convex and deformation, vertical and flat, and need to use special tools to round it.
- 2. The finished flanging short pipe is welded on the pipe, and the O-shaped rubber seal ring and stainless steel seal ring installed on both sides are inserted into the flange with groove ring for sealing. The inner diameter of the inner hole of the sealing ring is the same as that of the pipe, and then the flange hole is connected with bolts. The bolt assembly needs to be tightened symmetrically. When tightening the weld neck flange, please pay attention to the sealing of each joint and meet the required specifications.
