Anti-rust maintenance and inspection methods for straight seam welded pipe

The production process of straight seam welded pipe is simple, the production efficiency is high, the cost is low, and the development is rapid. The strength of spiral welded pipes is generally higher than that of straight seam welded pipes. Welded pipes with larger diameters can be produced from narrower billets, and welded pipes with different diameters can also be produced from billets of the same width. However, compared with straight seam pipes of the same length, the weld length is increased by 30~100%, and the production speed is lower. Therefore, smaller-diameter welded pipes mostly use straight seam welding, while large diameter welded pipes mostly use spiral welding.

Straight seam welded pipe rust removal and maintenance method:
However, the maintenance of straight seam welded pipe equipment has become a headache. Straight seam welded pipe equipment plays an important role in life and work. It is generally required that the surface of straight seam welded pipe fittings reaches a nearly white level (Sa2.5). The practice has proved that it is suitable for the construction technology of epoxy, vinyl, phenolic, and other anti-corrosion coatings commonly used in straight seam welded pipe fittings. Using this level of rust removal can almost remove All oxide scale, rust, and other dirt, and the depth of the anchor pattern reaches 40~100μm, which fully meets the adhesion requirements between the anti-corrosion layer and the steel pipe. The spray (throwing) rust removal process can be achieved with lower operating costs and stability and reliability. Near white level (Sa2.5 technical conditions). When rust occurs in the straight seam welded pipe, it should be treated according to the special rust removal methods and methods to ensure the high quality and performance of the straight seam welded pipe. It can be used in different industries and fields and is a good choice for the construction industry. made important contributions and roles.

Spray (throw) abrasives for straight seam welded pipes:
To achieve the ideal rust removal effect, the abrasive should be selected according to the hardness of the surface of the straight seam welded pipe equipment, the original rust level, the required surface roughness, the coating type, etc. For single-layer epoxy, two-layer, or three-layer polyethylene coating It is easy to achieve the ideal rust removal effect by using a mixed abrasive of steel sand and steel shot. Steel shot has the function of strengthening the steel surface, while steel grit has the function of etching the steel surface. A mixed abrasive of steel sand and steel shot (usually the hardness of steel shot is 4050HRC and the hardness of steel sand is 5060HRC) can be used on various steel surfaces. Even when used on C- and D-class rusted steel surfaces, the rust removal effect is also very good.

Rust removal speed of straight seam welded pipe:
That is, the total kinetic energy E applied to the steel pipe by the abrasive per unit time and the kinetic energy E1 of the single-grain abrasive. The rust removal speed of the steel pipe depends on the type of abrasive and the displacement of the abrasive. In the formula: m abrasive spray (throwing) amount; V abrasive running speed; m1 single-grain abrasive. The size of m is related to the abrasive crushing rate. The size of the crushing rate directly affects the cost of surface treatment operations and the cost of rust removal equipment. When the equipment is fixed, m is a constant and y is a constant, so E is also a constant. However, due to the crushing of the abrasive, m1 changes. Therefore, abrasives with a lower loss rate should generally be selected, which will help improve the cleaning speed and long-term maintenance.

The particle size and ratio of abrasives for straight seam welded pipes:
To obtain better uniform cleanliness and roughness distribution, the particle size and proportion design of the abrasive are very important. Too much roughness will easily cause the anti-corrosion layer to become thinner at the peaks of the anchor lines; at the same time, because the anchor lines are too deep, bubbles will easily form in the anti-corrosion layer during the anti-corrosion process, seriously affecting the performance of the anti-corrosion layer.

High-intensity impact with large-grained abrasives cannot be used alone. Too small roughness will cause the adhesion and impact strength of the anti-corrosion layer to decrease. For severe internal pitting corrosion. It is also necessary to rely on small particles to grind away the corrosion products to achieve the cleaning effect. At the same time, a reasonable ratio design can not only slow down the wear of the abrasive on the pipe and nozzle (blade) but also greatly improve the utilization rate of the abrasive. Usually, the particle size of steel shot is 0.81.3mm, and the particle size of steel grit is 0.41.0mm, of which 0.51.0mm is the main component. The sand shot ratio is generally 58. It should be noted that in actual operation, the ideal ratio of steel sand and steel shot in the abrasive is difficult to achieve. The reason is that the hard and brittle steel sand has a higher breakage rate than the steel shot. For this reason, the mixed abrasives should be sampled from time to time during operation, and new abrasives should be added to the rust remover according to the particle size distribution. Moreover, among the new abrasives added, steel grit should account for the majority.

Various detection methods for straight seam welded pipes:
Currently, magnetic powder is widely used to detect straight seam welded pipes. Magnetic testing can generally only detect defects on the surface of welded pipes. Many problems cannot be well reflected and are usually judged based on experience. Then the purpose is to use waves and rays together. This kind of detection can sensitively detect defects in welded pipes, but there are also defects in this detection method, and it cannot determine the material, shape, size, etc. of the welded pipes.

The current detection methods are all physical detection methods, which can not only reduce damage to the material but also accurately reflect material defects and obtain better information. However, everything has two sides, and this detection method is not absolutely reliable. It is still necessary to tell the answer based on the customer's own experience during the long-term use and purchase process. We also remind everyone to choose straight seam welded pipes with a good reputation and good reputation during the purchasing process, which can also reduce losses.