1. Under the condition of not affecting the welding of the nozzle, the reserved length of the epoxy powder at the end of the polyethylene layer should be appropriately increased to prevent the 3PE anti-corrosion warping caused by the long stacking time of the steel pipe and the serious metal corrosion of the pipe end.
2. When
anticorrosive steel pipes are stacked in the open air for a long time, they should be covered at the pipe ends to prevent rainwater from corroding and causing serious corrosion of the pipe ends.
3. If the pipeline construction period is long, weldable anti-rust paint can be painted on the bare metal of the pipe end to prevent the 3PE anti-corrosion layer from warping due to corrosion during storage.
4. Strictly control the grinding quality of the welding seam reserved at the pipe end. The outsides of the polyethylene groove at the weld is the same as the other parts of the pipe body. Keep the epoxy powder longer than 20mm to prevent the bottom of the epoxy powder at the weld from being corroded first and causing the 3PE anti-corrosion layer of warp.
Attention should be paid to the grinding of pipe end welds:
1) From the beginning of the welding seam grinding to the polyethylene chamfer, there should be a flat section of the polyethylene layer of 10-20mm with no excess weld height and the same as the pipe body to ensure the extrusion and bonding of the polyethylene groove at the pipe end quality.
2) The reinforcement of the weld seam after grinding should be as flush as possible with the pipe body, and there should be no obvious reinforcement to prevent the epoxy powder from being polished off when grinding the chamfer of the polyethylene layer.
3) The chamfer of the undressed top of the weld and the transition section of the repaired place should also be the same as the chamfer of the polyethylene layer (≤30°) so that the squeezing force of the squeeze roller can evenly press the polyethylene layer To prevent the polyethylene layer from curling due to poor adhesion of the anti-corrosive layer at the groove.
5. The epoxy powder coating of the reserved section can delay the edge warping caused by corrosion only when the protection is complete. Domestic pipe end polyethylene bevel processing is done by steel wire wheel grinding, which will damage the epoxy powder coating. The bevel should be machined instead, and the bottom layer of the knife-edge should be limited by a device to control the cutting depth of the tool, so as not to damage the epoxy powder coating.
