1. Repair of oral cavity
In order to ensure the quality of welding, welding is carried out before comprehensive inspection and correction, so that pipe ends, oblique angles, blunt edges and roundness meet the requirements of interface size. Individual steel pipes need to be grooved in the field, cut by gas welding, remove slag and grind with grinding wheel.
The counter operation procedure is: checking the size of the interface connector clearing the chamber determining and adjusting the staggered position of the longitudinal joint of the steel pipe the first straight line of the pipe adjusting the gap size of the counterpart leveling mouth straight line spot welding.


2. Welding
Arc welding is used for interface welding. Once it is down to the base, it can survive twice. Each welding is welded once, and each layer leads to arc staggering.


A. Pipe joints should first be in the mouth, slag, pipe end corner groove, blunt edge, gap, should conform to the specifications; do not narrow gap welding in gap welding or gap between welding methods.
B. Mouths should be level with the wall. The length of 300 mm should be arranged in the order of the inner wall of the interface so as to close the wrong port. The allowable part of the inspection should be 0.2 times the wall thickness and not more than 2 mm.
C. Longitudinal and circumferential welds should meet the following requirements: longitudinal welds should be about 45 degrees apart from the semi-circle of the vertical line of the pipeline; welds of reinforcing bars and reinforcing rings should be staggered on the longitudinal welds, spacing should not be less than 100 mm; reinforcing rings of circumferential welds should not be less than 50 mm; cross welds should not be used in any position of the pipeline.
D. In positioning welding, all pads (or grades) should be positioned in the same way as official welding, but the diameter of the electrode can be fine. The welding current of the positioning weld should be greater than that of the formal welding, usually 10% - 15%, to ensure penetration.
E. Pipeline welding: The quality of weld seam must comply with the relevant regulations of 4.2 in GB50268-97. The weld seam should be smooth, uniform in width, penetrate through the root, without obvious concave and convex defects and undercut phenomenon. The weld reinforcement should be higher than 2 mm on the pipe surface and 2-3 mm on the edge of the weld.
F. When welding pipes and flanges, the pipes should be inserted into two thirds of the flanges, and the flanges and pipes should be vertical, which coincide with the axis.