In the traditional production technology, the anti-corrosion insulation tube molding is formed by a pill rust production line, a three-layer PE anti-corrosion layer molding production line and a foam jacket molding production line. On the basis of summarizing the three-layer PE anti-corrosion production line and the inner-diameter one-step foam jacket production line, Tianhua Chemical Machinery and Automation Research and Design Institute has developed a production line that can be compatible with foam insulation pipe production on the three-layer PE anti-corrosion pipe production line. It consists of a pill rust production line and a three-layer PE compatible foam jacket insulation molding production line. Because the pill derusting production line is an independent production process in the process of forming anticorrosive pipe and thermal insulation pipe, it is not mentioned in this paper.
1 Molding technology The production of three-layer PE anti-corrosion layer firstly forms an anti-corrosion layer with a thickness of more than 80 Mm on the surface of the heated steel pipe by electrostatic spraying technology. The molten primer and polyethylene are coated or wound on the surface of the steel pipe by annular extrusion. The method forms an adhesive layer and a polyethylene outer protective shell, and forms a three-layer PE anti-corrosion layer by water cooling. Ring extrusion powder and penetrant inspection were qualified. The pressure values ​​of the hydraulic test and the air tightness test are 2 27 MPa, respectively, which meet the design requirements.
One year after the completion of the production of the spherical tank (end of 2002), the can opening inspection was carried out, no defects were found, the safety status was rated as level 1 (the highest level), and after three years (end of 2005), internal and external inspections were carried out. Everything is normal and the security status level is still set to level 1.
The coating technology adopts a special annular die, extruding a cylindrical molten bottom tape and a polyethylene belt, and exerts a three-layer PE anti-corrosion layer on the surface of the anti-corrosion layer of the steel pipe through negative pressure and water cooling, and the advantage is that the anti-corrosion layer is formed. The film is good, no overlap; the disadvantage is that the mold used is many, suitable for the three-layer PE molding of small and medium-diameter steel pipe (generally less than D600 mm steel pipe), which has certain limitations in the application of large-diameter steel pipe. The winding forming technology is divided into an upper winding forming process and a side winding forming process. The processes of the two forming technologies are all uniform, and a special flat plate die is used to extrude a fixed width of hot melt tape and polyethylene tape on the surface of the rotating steel pipe. The winding is carried out, and an anti-corrosion layer is formed by a special pressure roller and water cooling. Side winding is more winding technology, the distance between the die lip and the steel tube is easy to adjust, the extrusion equipment and its mold occupy a small space, easy to operate, the film stretch and the adjustment of the lip gap size, special pressure roller and extruder The molds are installed separately and it is easy to adjust their positions. After comparing the above several methods, the side winding technique was selected as the three-layer PE molding process.
(Finish)
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