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Derusting method of spiral pipe

Views: 4     Author: Site Editor     Publish Time: 2020-07-22      Origin: Site

    Spiral pipe is also called spiral steel pipe or spiral welded pipe. It is made by rolling low-carbon structural steel or low-alloy structural steel strip according to a certain spiral angle (called forming angle) into a tube blank, and then welding the pipe seam together. It can produce large-diameter steel pipes from narrower strip steel. Spiral pipes are mainly used for oil and natural gas pipelines, and their specifications are expressed by outer diameter * wall thickness. Spiral pipes can be welded on one side or on both sides. Welded pipes should ensure that the water pressure test, the tensile strength of the weld and the cold bending performance meet the requirements.

Derusting method of spiral pipe:

1. Pickling and rust removal. Generally, two methods are used for pickling treatment, namely chemical and electrolysis. Pipeline anticorrosion only needs to use chemical pickling, which can remove oxide scale, old coating, rust, and sometimes it can be used as a reprocessing after sandblasting and rust removal. Although chemical cleaning can make the surface reach a certain degree of cleanliness and roughness, its anchor pattern is shallow and easily pollutes the environment.

2. Spraying (throwing) to remove rust. This rust removal method uses a high-power motor to drive the spray (projection) blade to rotate at a high speed, so that the steel shot, iron wire section, steel grit, mineral and other abrasives are sprayed (projected) on the surface of the steel pipe under the action of centrifugal force. It can completely remove rust, oxide and dirt, and the steel pipe can achieve the required uniform roughness under the action of the violent impact and friction of the abrasive. After spraying to remove rust, it can not only expand the physical adsorption of the pipe surface, but also enhance the mechanical adhesion of the anti-corrosion layer to the pipe surface. Therefore, spray rust removal is an ideal rust removal method for pipeline anticorrosion. Generally speaking, shot blasting (sand) rust removal is mainly used for pipe inner surface treatment, and shot blasting (sand) rust removal is mainly used for pipe outer surface treatment.

    Several issues should be paid attention to when using spray (throwing) to remove rust: ◆Rust removal grade. For the construction process of epoxy, vinyl, phenolic and other anticorrosive coatings commonly used in steel pipes, the surface of the steel pipe is generally required to reach a near-white level (Sa2. 5). Practice has proved that the use of this rust removal grade can remove almost all oxide scale, rust and other dirt. The depth of the anchor pattern reaches 40-100μm, which fully meets the requirements of the adhesion of the anti-corrosion layer and the steel pipe. The rust process can achieve near-white (Sa2.5) technical conditions with low operating costs and stable and reliable quality. ◆Spray (throw) abrasives should be selected according to the hardness of the steel pipe surface, the degree of original corrosion, the required surface roughness, the type of coating, etc., for single-layer epoxy, two-layer or three-layer polyethylene coating, steel The mixed abrasive of sand and steel shot is easier to achieve the ideal rust removal effect. Steel shot has the effect of strengthening the steel surface, while steel grit has the effect of etching the steel surface. A mixed abrasive of steel grit and steel shot (usually the hardness of steel shot is 40-50 HRC, and the hardness of steel grit is 50-60 HRC. It can be used on various steel surfaces, even on C-grade and D-grade rusted steel surfaces. , The rust removal effect is also very good.  

    The rust removal speed of the steel pipe depends on the type of abrasive and the displacement of the abrasive, that is, the total kinetic energy E of the abrasive applied to the steel pipe per unit time and the kinetic energy E1 of the single particle abrasive. When the equipment is fixed and unchanged , M is a constant, y is a constant, so E is also a constant, but because the abrasive is broken, m1 changes. Therefore, the abrasive with a lower loss rate should generally be selected, which will help improve the cleaning speed and extend the life of the blade.

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