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How to detect the corrosion performance of flanges

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The use of flanges in industrial structural parts is mainly to improve the connection function and keep the pipelines sealed and leak-free. However, many flanges will undergo corrosion and aging after being used for some time, thus losing the sealing effect. Therefore It is very necessary to conduct anti-corrosion testing of flanges regularly. Here I would like to share with you the process of measuring flange corrosion.

First of all, it must be confirmed that the flange must be maintained and inspected regularly. After corrosion occurs, it usually manifests as thinning of the flange wall and the appearance of local pits and pits. The causes and methods of internal corrosion of stainless steel flanges need to be carried out according to certain methods and principles. The flange corrosion detection methods that are widely used at home and abroad are the magnetic flux leakage method and ultrasonic detection method.

Ultrasonic method The Ultrasonic testing method uses the pulse reflection principle of ultrasonic waves to measure the thickness of the pipe wall after corrosion. Magnetic flux leakage method The basic principle of magnetic flux leakage method detection is based on the high magnetic permeability of ferromagnetic materials. The magnetic permeability at the corrosion defects of the flange is much smaller than the magnetic permeability of the flange. It is magnetized under the action of an external magnetic field. When there are no defects in the flange, most of the magnetic field lines pass through the steel pipe. At this time, the magnetic field lines are evenly distributed; when there are defects inside the flange, the magnetic field lines bend and some of the magnetic field lines leak out of the surface of the steel pipe. By detecting the leakage flux escaping from the surface of the magnetized flange, you can determine whether defects exist.

In addition, when testing, the probe is emitted vertically to the inner wall of the flange. The probe first receives the reflected pulse from the inner surface of the pipe wall, and then the ultrasonic probe receives the reflected pulse from the outer surface of the pipe wall. This pulse is consistent with the reflected pulse from the inner surface. The distance between them reflects the thickness of the pipe wall. The actual inspection of elbows needs to be carried out by the actual conditions and instructions, and ultrasonic inspection can be a good way to check.

The ultrasonic detection method is also suitable for thickness measurement and metal performance measurement of other metal structural parts.




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