Magnetic particle testing or penetration testing can effectively detect surface defects such as surface cracks, folding, heavy skins, hair lines, pinholes and so on. For ferromagnetic materials, because of its high sensitivity, magnetic particle detection method should be given priority; for non-ferromagnetic materials, such as stainless steel seamless tubes, permeation detection method should be used.


When the cut-off margin at both ends is small, the detection device can not detect both ends effectively because of its structure, and the end is the most likely part with cracks or other defects. If there is a potential crack tip tendency, the installation of welding thermal effect can also be used for potential crack propagation. Therefore, after welding, attention should also be paid to the detection of seamless steel pipe in a certain area, and the expansion defects of steel pipe head should be found in time.


When using austenitic seamless steel pipe, when the insulation layer is damaged or where rain water may permeate, attention should be paid to the seepage test to find out the defects such as stress corrosion cracking or pitting corrosion.


However, the detection of magnetic powder or penetration can only detect the outer surface of the steel pipe, and the inner surface of the defect is powerless. It is necessary to detect the inner surface by ultrasonic testing, especially the crack-like defects.