NEWS

1. Basic requirements for weld appearance of straight seam steel pipe
Before NDT of straight seam steel pipe, the weld appearance inspection shall meet the requirements. The general requirements for the appearance of welds and the surface quality of welded joints of straight seam steel pipes are as follows:
The welding appearance shall be well formed, and the width shall be 2mm over the groove edge. The weld leg height of fillet weld shall meet the design requirements, and the appearance shall be smooth transition.
Welded joint surface
(1) Cracks, incomplete fusion, air holes, slag inclusions and splashes are not allowed.
(2) The weld surface of pipes with design temperature lower than - 29 ° C, stainless steel and alloy steel pipes with high hardening tendency shall not have undercut. The undercut depth of welds of pipes of other materials shall be greater than 0.5mm, the continuous undercut length shall not be greater than 100mm, and the total length of undercut on both sides of the weld shall not be greater than 10% of the total length of the weld.
(3) The weld surface shall not be lower than the pipe surface. The weld reinforcement shall be no more than 3mm (it is the Zui large width of the groove after welding joint assembly).
(4) The misalignment of welded joints shall be no more than 10% of the wall thickness and no more than 2mm.
2. Surface NDT
Selection principle of surface nondestructive testing method for straight seam steel pipes: magnetic particle testing shall be used for ferromagnetic steel pipes; For non ferromagnetic steel pipes, penetrant testing shall be selected.
For the welded joints with delayed crack tendency, the surface NDT shall be carried out after the welding is cooled for a certain time; For welded joints with reheat crack tendency, the surface NDT shall be conducted once after welding and once after heat treatment.
The application of surface nondestructive testing shall be carried out in accordance with the standard requirements. The detection objects and application occasions are generally as follows:
(1) External surface quality inspection of pipe materials.
(2) Important butt weld surface defect detection.
(3) Important fillet weld surface defect detection.
(4) Detection of surface defects of welded joints of important socket welding and jumper tee branch pipes.
(5) Surface defect detection after pipe bending.
(6) Groove detection of welded joints with large quenching tendency.
(7) Detection of non austenitic stainless steel pipe groove with design temperature lower than or equal to minus 29 ℃.
(8) Inspection after back gouging of welds with back gouging specified for double-sided Weldments
(9) When oxyacetylene flame is used to cut the welding fixture on the alloy pipe with hardening tendency, the defect detection of the grinding part.
3. Radiographic testing and ultrasonic testing
The main objects of radiographic testing and ultrasonic testing are butt joints of straight seam steel pipes and butt joints of butt welded pipe fittings.
The selection of NDT methods shall be in accordance with the design documents. The radiographic testing method shall be used for testing the welded joints of titanium, aluminum and aluminum alloy, copper and copper alloy, nickel and nickel alloy.
For welds with delayed crack tendency, the radiographic inspection and ultrasonic inspection shall be carried out after the welding is cooled for a certain time.
When the main pipe in the jacket pipe has circumferential welds, the welds shall be subject to 100% radiographic testing, and the concealed operation can be carried out only after the pressure test is qualified.
The welded joints covered by the reinforcing ring or the bearing pad on the pipeline shall be subject to 100% radiographic testing and can be covered only after they are qualified.
Non destructive testing shall be carried out after the appearance inspection is qualified, radiographic and ultrasonic testing shall be carried out after the surface non-destructive testing, and the welding can be continued after the inspected welds are qualified.