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1. process comparison: since the plastic-coated steel pipe is constructed under no pressure, the lining layer has no internal stress. the lining layer and the steel pipe are a one-step process, and the construction process is simple. the plastic-lined steel pipe first needs to extrude plastic raw material into a plastic pipe through an extruder, the plastic pipe has internal stress, and then a layer of adhesive is coated on the surface of the plastic pipe, and finally inserted into the steel pipe, pressurized, and heated to form a plastic-lined steel pipe, which can be said to be a two-step process, with internal stress and complicated construction technology.
2. comparison of the bonding force between the lining layer and the steel pipe: the plastic-coated steel pipe is made of a powder coating with a very small particle size, which is heated and spin-coated on the inner surface of the steel pipe, and then slowly cooled. the plastic lining has no internal stress, and the lining layer is fully combined with the steel pipe, so the binding force is good. plastic-lined steel pipes are plastic pipes and steel pipes that participate in the bonding effect to determine their quality. first, there is an ellipticity tolerance in the pipes, and it is impossible to fully bond between the pipes; second, the plastic-lined composite steel pipes are high-frequency welded pipes. in the presence of weld seams, it is impossible to fully combine the pipes and pipes, so the bonding force is poor. moreover, when the plastic pipe in the plastic-lined pipe is in place, it is necessary to produce plastic deformation. if the plastic deformation is not sufficient, the shrinkage internal stress of the pipe diameter will be generated. due to the large difference in the linear expansion coefficients of steel and plastic, the inner plastic will shrink at the pipe head when the bond is not strong, and the pipe end is easily damaged. if the bond is not good, the steel-plastic delamination phenomenon will also occur.
3. steel pipe caliber, thickness, length, and comparison: there is no caliber limit for plastic-coated steel pipes, and the thickness of the lining layer can also be selected arbitrarily. now, what kind of products can be produced including large containers, and plastic-lined steel pipes are limited by caliber and length, generally only 1"-6" (dn25mm-150mm), and only 12" (dn300mm) ); the general length can only reach about 6 meters.
4. economical comparison: due to the one-step construction of plastic-coated steel pipes, time and energy are saved. the same nominal diameter is only because the thickness of the plastic pipe wall of the plastic-lined steel pipe is between 1.25-2mm, while the lining of the plastic-coated steel pipe is generally between 0.5-1mm. there are also few materials. due to its shortcomings, the service life of plastic-lined steel pipes is not as good as that of plastic-coated steel pipes.