1. Repair the mouth
In order to ensure the welding quality, a comprehensive inspection and correction must be carried out before welding to ensure that the ends, bevels, bell edges, roundness, etc. of the spiral steel pipe meet the interface requirements. Size, when individual steel pipes need to be beveled in the field, gas welding is used to cut, remove the slag, and then grind with a grinding wheel.
The operation procedure is: check the size of the interface connector - clear the air chamber - determine and adjust the staggered position of the longitudinal joint of the steel pipe - the straightness of the first pipeline - adjust the gap size of the counterpart - level the mouth at a right angle and weld with one point in a straight line
2.Welding
Interface welding uses arc welding, with one base placement and two survival times. Each weld is welded once, and the welds produced by the arc on each layer must be staggered.
A. Pipe joints should be preceded by mouth, slag, pipe end bevel angle, blunt mouth, and gaps should meet specifications. Gap welding cannot be used between gaps or gap welding methods should be used to reduce gap welding.
B. The port should be flat with the wall, and a 300mm long ruler should be arranged in sequence with the inner wall to close the wrong port to allow local inspection. It should be 0.2 times the thickness of the guard and not larger than 2 mm.
C. The positions of the longitudinal welds and circumferential welds should meet the following requirements. The longitudinal welds should be approximately 45 degrees from the semicircle of the vertical line of the pipe. The welds of the reinforced spiral steel pipe and the reinforced ring should be staggered in the longitudinal direction with no spacing. It should be less than 100mm; the cross-section of the surrounding coal seam of the reinforced ring pipe should not be less than 50mm; there should be no cross-shaped welds at any position of the pipe.
D. When positioning welding, the positioning of all welding pads (or grades) should be the same as for formal welding, but the welding rods can be fine. The welding current for positioning welds should be selected to be greater than the current for formal welding, usually 10%-15%, to ensure penetration.
E. Pipe welding: The quality of the weld must comply with the relevant provisions of GB50268-97 4.2. The weld should be flat, uniform in width, with deep root penetration, and no obvious protruding defects or undercuts. The weld reinforcement should be about 2mm higher than the pipe surface. , connect the edge of the groove by 2-3 mm.
F. For welding of pipes and flanges, the pipe should be inserted two-thirds into the flange, the flange and the pipe should be vertical, and the two should coincide with the axis.
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