Surface NDT methods of straight seam steel selection principles: magnetic iron pipe should be used in magnetic particle testing; non-ferromagnetic steel should be used in penetration testing. Delayed cracking tendency of welded joints, the surface should be non-destructive testing after welding cooling certain time; reheat cracking tendency of welded joints, the surface should be in non-destructive testing and post-weld heat treatment once each. 
Surface non-destructive testing applications in accordance with the standard requirements that detects objects and applications in general as follows:
(1) An outer surface of the tube material quality inspection.
(2) Important butt weld surface defect detection.
(3) Important fillet surface defect detection.
(4) Important socket weld and jumper tee branch pipe defect detection.
(5) Pipe bending surface defect detection.
(6) The material tends to quench detection larger groove welded joints.
(7) The design temperature is below zero or non-austenitic stainless steel pipe beveling detected 29 degrees Celsius.
(8) The provisions of the double-sided weldment after weld gouging gouging detection
(9) When using oxyacetylene flame cutting jig welded pipes alloy hardening tendency on when grinding parts defect detection.