In the anti-corrosion construction of oil and gas pipelines, straight seam steel pipes are often used. The surface treatment of this welded pipe is one of the key factors that determine the anti-corrosion service life of the pipeline, and it is also a prerequisite for whether the anti-corrosion layer and the straight seam steel pipe can be firmly combined. According to the research of professional institutions, the service life of anti-corrosion coating depends on factors such as coating type, coating quality, and construction environment. The surface treatment of the straight seam steel pipe affects about 50% of the service life of the anti-corrosion layer. Therefore, the surface treatment method of the straight seam steel pipe should be continuously improved in strict accordance with the requirements of the anti-corrosion coating on the surface of the straight seam steel pipe.
There are mainly the following methods for removing rust from straight seam steel pipes:
1. Cleaning
Solvents and emulsions are used to clean the steel surface to remove oil, grease, dust, lubricants and similar organic matter, but it cannot remove rust, oxide scale, flux, etc. These measures can only prevent the rust of the straight seam steel pipe, but cannot remove the rust on the straight seam steel pipe.
2. Pickling
It is a method often used in the process of rust removal of straight seam steel pipes. In the actual anti-corrosion process of the pipeline, some acid chemicals are used to wash the rust to achieve the purpose of removing the rust. Pickling has many advantages, but there are also certain drawbacks. For example, it is easy to pollute the surrounding environment when pickling is carried out, and if the pickling uses chemicals improperly, not only can it not remove the rust, but it may also damage the straight seam steel pipe.
3. Tools for rust removal
Mainly use tools such as wire brushes to polish the steel surface. Can remove loose oxide scale, rust, welding slag, etc. Derusting with hand tools can reach Sa2 level. Derusting of electric tools can reach Sa3 level. If the steel surface has strong iron scales. The rust removal effect of the tool is not ideal, and it cannot meet the standards required for anti-corrosion construction.
4. Spraying and rust removal
The high-power motor drives the spraying blade to rotate at high speed, so that the steel balls, steel grit, iron wire segments, minerals and other abrasives are sprayed on the surface of the straight seam steel pipe under the strong centrifugal force of the motor. Not only can completely remove oxides, rust and dirt, but also the straight seam steel pipe can achieve the required uniform roughness under the strong impact and friction of the abrasive.
After spraying to remove rust, it can not only expand the physical adsorption of the pipe surface. It can also enhance the mechanical adhesion between the anti-corrosion layer and the pipe surface. Therefore, spray rust removal is an ideal rust removal method for pipeline anticorrosion. Generally speaking, shot blasting is mainly used for the inner surface treatment of pipelines, and shot blasting is mainly used for the outer surface treatment of straight seam steel pipes. In the production process, the relevant technical indicators for rust removal should be strictly required. Prevent the second damage to the straight seam steel pipe caused by operating errors.
Straight seam steel pipe is not only used for conveying liquid and powdery solids, for heat exchange and manufacturing mechanical parts and containers, but also an economical steel pipe. The use of steel pipes to make the grids, pillars and mechanical supports of the building structure can reduce weight, save 20-40% of metal, and can realize factory mechanized construction. Using steel pipes to manufacture highway bridges not only saves steel, simplifies the structure, but also greatly reduces the area of the protective layer, saving investment and maintenance costs.
Nowadays, we have a wide range of applications on steel pipes, but rust will inevitably occur during the use of steel pipes. The rusty steel pipe will affect its normal use. Therefore, if rust is found on the steel pipe, it needs to be cleaned up in time. Through relevant comparative tests, it is verified that the yield pressure of the straight seam steel pipe and the steel pipe is consistent with the actual value and the theoretical value of the burst pressure, with a small deviation. However, the yield pressure and burst pressure are lower than steel pipes. The blasting test also showed that the circumferential deformation rate of the blasting port of the straight seam steel pipe was significantly greater than that of the steel pipe.
Tips: Straight seam steel pipe is a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. Straight seam steel pipes can be divided into high-frequency straight seam steel pipes (ERW Pipe) and submerged arc welded straight seam steel pipes (LSAW Pipe) according to the production process. Straight seam welded pipe has simple production process, high production efficiency, low cost and rapid development.
ASTM A53 Grade B is the material under the American steel pipe standard, API 5L Gr.B is also the American standard material, A53 GR.B ERW refers to the electric resistance welded steel pipe of A53 GR.B; API 5L GR.B Welded refers to the material Welded steel pipe of API 5L GR.B.
