How to detect the corrosion performance of flanges

The use of flanges in industrial structures is mainly to improve the connection function and maintain pipeline sealing without leakage. However, many flanges will experience corrosion and aging after being used for a period of time, resulting in a loss of sealing effect. Therefore, it is necessary to conduct regular corrosion resistance tests on flanges. Here, I would like to share with you the process of measuring flange corrosion.

Firstly, it must be confirmed that the flange must be regularly maintained and inspected. After corrosion occurs, it usually manifests as sparse flange walls and the appearance of localized pits. The causes and methods of internal corrosion of stainless steel flanges need to be based on certain methods and principles. The widely used flange corrosion detection methods both domestically and internationally are magnetic flux leakage method and ultrasonic testing method.

Ultrasonic method: The ultrasonic testing method uses the principle of ultrasonic pulse reflection to measure the thickness of the corroded pipe wall.

Magnetic flux leakage method: The basic principle of magnetic flux leakage detection is based on the high magnetic permeability of ferromagnetic materials. The magnetic permeability at the corrosion defect of the flange is much smaller than that of the flange. It is magnetized under the action of an external magnetic field. When the flange has no defects, most magnetic field lines pass through the steel pipe. At present, the magnetic field lines are evenly distributed. When there are defects inside the flange, the magnetic field lines bend and some magnetic field lines leak out from the surface of the steel pipe. By detecting the leakage flux escaping from the surface of the magnetized flange, you can determine whether there are defects.

Additionally, during testing, the probe will emit vertically onto the inner wall of the flange. The probe first receives reflected pulses from the inner surface of the tube wall, and then the ultrasonic probe receives reflected pulses from the outer surface of the tube wall. This pulse is consistent with the reflected pulse on the inner surface. The distance between them reflects the thickness of the pipe wall. It is necessary to conduct an actual examination of the elbow based on actual conditions and instructions, and ultrasound examination may be a good method for examination.
The ultrasonic testing method is also applicable to thickness measurement and metal performance measurement of other metal structural parts.