In the industry, 3PE anti-corrosion equipment for steel pipes with a diameter below 1200mm is classified as small-caliber equipment, while that above 1200mm is defined as large-caliber equipment. This paper focuses on the analysis of ultra-large-caliber anti-corrosion equipment with a diameter of 4220mm.
Based on the company’s long-term R&D experience, the technical and process standards of 4220mm-diameter equipment are far higher than those of conventional large-caliber counterparts. In terms of structure and load bearing, the ultra-heavy steel pipe weighs over 100 tons, requiring heavy-load and high-rigidity roller tables. Pipe deformation and uneven coating thickness tend to occur easily.
Temperature control becomes much more challenging. The thick pipe wall brings large heat capacity, resulting in an axial and circumferential temperature difference of 20 to 30℃, which may cause abnormal solidification and interlayer peeling of the anti-corrosion coating.
The large pipe circumference raises difficulties in coating spraying matching with increased thickness deviation, commonly leading to material accumulation at the bottom and thin coating on the top. The sharply rising PE extrusion volume also greatly hinders melt distribution and winding synchronous control.
Slow cooling of large pipes easily causes coating warping and cracking. Its production line speed is much lower, accompanied by substantially higher equipment investment, energy consumption and commissioning costs.
