How to detect the corrosion performance of flanges

The use of flanges in industrial structural parts is mainly to improve the connection function and keep the pipeline sealed without leakage. However, many flanges will corrode and age after a period of use, thus losing the sealing effect, so it is very necessary to perform anti-corrosion tests on flanges regularly.

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

Ultrasonic method. The Ultrasonic detection method uses the pulse reflection principle of ultrasonic waves to measure the thickness of the pipe wall after corrosion. The basic principle of the leakage flux method is based on the high magnetic permeability of ferromagnetic materials. The magnetic permeability of the flange corrosion defect is much smaller than that of the flange. The flange is magnetized under the action of an external magnetic field. When there is no defect in the flange, most of the magnetic lines of force pass through the steel pipe, and the magnetic lines of force are evenly distributed; when there is a defect inside the flange, the magnetic lines of force bend, and some of the magnetic lines of force leak out of the steel pipe surface. By detecting the leakage flux escaping from the magnetized flange surface, it can be determined whether the defect exists.

In addition, during the detection, the probe emits an ultrasonic pulse 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. The distance between this pulse and the reflected pulse from the inner surface reflects the thickness of the pipe wall. In actual detection, elbows need to be carried out according to actual conditions and instructions. The ultrasonic method can be used to test the best method. The ultrasonic detection method is also applicable to the thickness measurement and metal performance measurement of other metal structural parts.