Welded joint
(1) No cracks, lack of fusion, pores, slag inclusions or splashes are allowed on the surface.
(2) The weld surface of steel pipes with a design temperature lower than -29 degrees, stainless steel and alloy steel pipes that are easier to harden shall not have undercuts. The depth of the weld undercut for pipes made of other materials should be greater than 0.5mm, the length of the continuous undercut should not be greater than 100mm, and the total length of the undercut on both sides of the weld should not exceed 10% of the total length of the weld.
(3) The weld surface shall not be lower than the pipe surface. The welding height does not exceed 3mm (the maximum width from the welding joint group to the rear groove).
(4) The reverse side of the welded joint should be no more than 10% of the wall thickness and no more than 2 mm.
2. Surface non-destructive testing Principles for selecting non-destructive testing methods for straight seam steel pipes: Magnetic particle testing should be used for steel pipes made of ferromagnetic materials; for steel pipes made of non-ferromagnetic materials, penetration testing should be selected.
For welded joints with a tendency of delayed cracking, a surface non-destructive inspection should be carried out after the welding has cooled for a certain period of time; for welded joints with a tendency of reheat cracking, a surface non-destructive inspection should be carried out after welding and heat treatment.
The application of surface non-destructive testing is carried out according to standard requirements. Objects and objects are typically used as follows:
(1) Quality inspection of the outer surface of the pipe.
(2) Detection of surface defects of important butt welds.
(3) Inspection of important fillet weld surface defects.
(4) Surface defect detection of important socket welding and tee and tee branch welding joints.
(5) Surface defect detection after pipe bending.
(6) Quench the material and detect the grooves through the welded joint.
(7) Inspect non-austenitic stainless steel pipe tanks with a design temperature lower than or equal to minus 29 degrees Celsius.
(8) Double-sided welds require inspection of the root of the weld after rooting.
(9) When welding fixings on alloy pipes that have a tendency to harden are cut by an oxyacetylene flame, defects in the complex parts are detected.
3. Radiation detection and ultrasonic inspection The main purpose of radiation detection and ultrasonic inspection is the butt joints of straight seam steel pipes and butt joints of butt welded steel pipe fittings. Select the non-destructive testing method based on the design documents. To inspect welded joints of titanium, aluminum and aluminum alloys, copper and copper alloys, nickel and nickel alloys, radiation detection methods should be used.
