1. Basic requirements for appearance of A53 ERW steel pipe weld
Before the non-destructive testing of A53 ERW steel pipe, the weld appearance inspection should meet the requirements. The general requirements for the appearance of the welded seam of the longitudinal steel pipe and the surface quality of the welded joint are as follows:
The welding appearance should be well formed, and the width should be 2mm on each side covering the edge of the groove. The height of the foot of the fillet weld should meet the design requirements, and the shape should transition smoothly.
Welded joint surface:
(1) Cracks, unfused, pores, slag inclusions, and splashes are not allowed.
(2) The weld surface of pipes with a design temperature lower than -29 degrees, stainless steel and alloy steel pipes with a greater tendency to harden, shall not have undercuts. The undercut depth of the weld of other materials should be greater than 0.5mm, the continuous undercut length should not be greater than 100mm, and the total undercut length on both sides of the weld should not be greater than 10% of the full length of the weld.
(3) The weld surface shall not be lower than the pipe surface. The remaining height of the weld is not more than 3mm. (the maximum width of the back groove of the welded joint assembly).
(4) The staggered side of the welded joint should not be more than 10% of the wall thickness and not more than 2mm.
2. Surface non-destructive testing
A53 Principles for the selection of surface non-destructive testing methods for ERW steel pipes: Magnetic particle testing should be used for ferromagnetic steel pipes; penetration testing should be used for non-ferromagnetic steel pipes.
For welded joints with delayed cracking tendency, the surface non-destructive inspection shall be carried out after the welding has cooled for a certain period of time; for welded joints with the tendency to reheat cracks, the surface non-destructive inspection shall be carried out after welding and after heat treatment.
The application of surface non-destructive testing is carried out in accordance with the requirements of the standard. The detection objects and applications are generally as follows:
(1) Quality inspection of the outer surface of the pipe material.
(2) Detection of surface defects of important butt welds.
(3) Detection of surface defects of important fillet welds.
(4) Detection of surface defects in the welding joints of important socket welding and jumper tee branch pipes.
(5) Surface defect detection after pipe bending.
(6) Groove detection of welded joints with larger material quenching tendency.
(7) Detection of grooves for non-austenitic stainless steel pipes whose design temperature is lower than or equal to -29 degrees Celsius.
(8) Double-sided weldments are inspected after root cleaning
(9) When using oxyacetylene flame to cut welding fixtures on alloy pipes with a tendency to harden, detect the defects in the grinding parts.
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-welded pipe fittings.
The selection of non-destructive testing methods is in accordance with the design documents. For welding joints of titanium, aluminum and aluminum alloys, copper and copper alloys, nickel and nickel alloys, radiographic testing methods should be used.
For welds with delayed cracking tendency, radiographic inspection and ultrasonic inspection shall be carried out after the welding has cooled for a certain period of time.
When the main pipe in the jacketed tube has a girth weld, the weld shall be subjected to 100% radiographic inspection, and the concealed operation can only be carried out after the pressure test is qualified.
The welded joints on the pipeline covered by the reinforcing ring or the support pad shall be subjected to 100% radiographic inspection and can be covered again after being qualified.
For welds that are required to undergo intermediate welding inspections, non-destructive testing should be carried out after the appearance inspection is qualified, radiography and ultrasonic testing should be carried out after surface non-destructive testing, and the inspected welds can be welded only after the qualification is qualified.