Quality inspection method for flanges

Quality inspection method for flanges

When there are dents on the surface of the flange,there are generally two commonly used methods of inspection:one is the leakage magnetic flux method for detecting the flange,and the other is the ultrasonic detection method for detecting the flange.Let's first explain ultrasonic waves.The propagation process of mechanical vibrations in a medium is called waves.The human ear can sense elastic waves with frequencies above 20 Hz and below 20000 Hz,so elastic waves in this frequency range are also called sound waves.Elastic waves with frequencies less than 20 hertz are also called infrasound waves,while elastic waves with frequencies higher than 20000 hertz are called ultrasonic waves.Neither infrasound nor ultrasound can be felt by the human ear.The ultrasonic detection method utilizes the principle of pulse reflection of ultrasonic waves to detect the thickness of corroded pipe walls.

During testing,the probe emits ultrasonic pulses vertically towards the inner wall of the large-diameter flange.The probe first receives reflected pulses from the inner surface of the pipe wall,and then it receives reflected pulses from the outer surface of the pipe wall.The distance between these pulses and the reflected pulses on the inner surface reflects the thickness of the pipe wall.

The basic principle of leakage magnetic flux detection is based on the high magnetic permeability of ferromagnetic materials.The magnetic permeability at the corrosion defect of large-diameter flanges is much smaller than that of flanges.Flanges are magnetized under the action of an external magnetic field.When there are no defects in the flange,the majority of magnetic field lines pass through the steel pipe,and the magnetic field lines are evenly distributed;When there are defects inside the flange,the magnetic field lines bend and some of them leak out of the surface of the steel pipe.Detecting the leakage magnetic flux escaping from the surface of the magnetized large-diameter flange can determine whether defects exist.