Two Methods to Test the Internal Corrosion of Pipe Fittings
For all kinds of stainless steel pipe and fittings, internal corrosion is a very common phenomenon. When the its inside corroded, the wall thickness of pipe fittings will become thinner, and steel pits and spot will appear in the surface, which will affect the service life of the fittings and bring safety concerns.
Currently, the most widely used test methods for stainless-steel pipe fittings are magnetic flux leakage and ultrasonic testing.
The principle of ultrasonic testing is to measure the wall thickness of pipe through ultrasonic pulse reflection. When testing, the probe will send ultrasonic pulse to the wall. Next, after probe received the reflection pulse from inner surface and outer surface of the tube, the thickness of tube wall then can be calculated.
Magnetic Flux Leakage Testing
The principle of magnetic flux leakage testing is based on the high permeability of ferromagnetic materials. After stainless-steel pipe fittings get corroded, the permeability at the corrosion part will be far less than other parts. And after pipe fittings being magnetized:
The magnetic lines will be even if there are no defects inside the pipe fittings;
The magnetic lines will bend, and surpass the surface of the pipe if there are defects inside the pipe fittings.
The defect can be determined by detecting the flux leakage from the magnetized surface.