Transverse Cracks Maintenance of LSAW Steel Pipe

Lateral cracks in the longitudinal seam submerged arc welded pipe appears after rework, in particular:
1. Confirm the defect
100% UT weld inspection of all welds, crack markings location, length, depth and direction. If the entire weld is defective, it is proposed to excavate the entire re-submerged arc welding, manual arc welding of local repair recommendations.


2, sliding preheat
Preheat temperature, preheat temperature ℃ 110-170, the weld on both sides of the test position is not less than 150mm, the heating range of defects about 500mm.


3, planing
Plane out the crack range at both ends, the integrity of the weld seam is not less than 50mm central planing, planing end to a smooth transition, the transition surface and the vertical line at least greater than 45 °. Planer carbon rod angle should be 60 ° or less, especially in the crack reaches an angle as small as possible.


4, polishing
No black after polishing, polished surface should be smooth transition, there should be no sharp pit.


5, PT
After cooling to the appropriate temperature for penetration testing (PT).


6, polishing
PT According to the test results, grinding, grinding so far no red line.


7, MT
After grinding to do magnetic particle inspection (MT), confirm no residual cracks, or grinding should be continued until the MT is not detected cracks so far.


8, preheat
Recommended preheat temperature ℃ 110-170, preheated weld temperature detection on both sides of the location of not less than 150mm, 500mm welding within the heating distance.


9, welding
Welding operations were carried out according to the instructions, the weld bead width no more than 15mm, can be in the driveway lane. Arc welding can be manual, submerged arc welding process.


10, after welding insulation, slow cooling


11, after welding heat treatment
Post-weld heat treatment is mainly the hydrogen diffusion stiffness, welding welding has been committed to "eliminate hydrogen treatment residual stress is low," stress relief heat treatment. Recommended heat treatment systems are: welding heat 200 ℃ and the ceramic layer is completed immediately after turning off the cold insulation 2h.


12, after welding testing
48h after welding, according to the requirements of non-destructive testing, confirm the repair qualified.