Transverse crack after lsaw steel pipe measures rework appear, specifically:
1. Confirm defect
All welds 100% UT inspection, crack marked location, length, depth and direction. If the entire weld has defects, the proposed dig out the entire re-submerged arc weld, partial repair is recommended SMAW.
2, Planing preheat
Preheating temperature is 110-170 ℃, preheating temperature weld both sides of the detection position is not less than 150mm, the heating is within the range of from defects around 500mm.
3, Gouging
Gouging out both ends of the range of cracks, weld integrity is not less than 50mm Outbound middle gouging, gouging ends gently to smooth the transition, the transition surface and a vertical line at least greater than 45 °. Gouging carbon rod angle should be at 60 ° or less, particularly in the crack to arrive at an angle as small as possible.
4, Polished
Polished to no black, polished surface after the transition should be smooth, there should be no sharp pit.
5, PT
After cooling to an appropriate temperature do penetrant testing (PT).
6, Polishing
PT based on test results, for grinding, grinding to no red line so far.
7, MT
After grinding to do magnetic particle testing (MT), confirmed that no residual crack, or should continue to polish until the MT is not detected until cracks.
8, Preheat
Recommended preheating temperature is 110-170 ℃, preheat temperature detection position of both sides of the weld is not less than 150mm, 500mm weld heating within the range of distances.
9, Welding
Welding operations carried out in accordance with the instructions, the bead width not exceeding 15mm, can lanes on the lane. Can SMAW or automatic submerged arc welding process.
10, After welding, insulation, slow cooling
11, Post-weld heat treatment
PWHT is mainly diffusion of hydrogen, lower residual stress after welding for stiffness weldment have devoted to "eliminate the hydrogen treatment," "stress relief heat treatment." Recommended heat treatment system are: immediately after completion of welding heat to 200 ℃ with a ceramic blanket, power off after slow cooling insulation 2h.
12, After the welding detection
After welding is completed 48h, according to the requirements of NDT inspection to confirm repair qualified.
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