1) Appearance defects such as crack, folding, heavy skin, hair grain, pinhole. Generally magnetic particle testing or soak detection is used. For ferromagnetic material, magnetic powder assay should be adopted preferentially, because it has higher flexibility of detection; for non-ferromagnetic material, such as stainless seamless steel pipe, soak test is used.

2) Steel pipe end defects. When obligate excision allowance is fewer, for the structural reasons of detection installation, the two ends sometimes can not get useful testing, which is the most likely to crack or other defects existing sites. If there are latent crack points, the welding heat may also lead to crack propagation. Thus, after butt we should also pay attention to the detection of will surely area of seamless steel pipe, and duly find out defect expansion in steel pipe end.

3) Defects such as stress corrosion crack or corrosive pitting. For online use austenitic seamless steel pipe, when shell damaged or there are sites for rain oozing, soak test is attentively needed, to detect stress corrosion crack or corrosive pitting.

4) Magnetic powder or soak testing can be useful in steel surface detection, but for defects of internal appearance they are not so effective. Internally, especially crack defect detection must be ultrasonic testing.