First, what are the cleaning methods for large-diameter steel pipes?
1. Shot blasting: A high-power motor drives blades to rotate at high speed, causing abrasives such as steel shot, steel grit, wire segments, and minerals to be blasted onto the surface of the large-diameter steel pipe under centrifugal force. This removes rust, oxides, and dirt, and the steel pipe achieves the required uniform roughness under the intense impact and friction of the abrasives.
2. Cleaning: Grease, dust, lubricants, and organic matter adhering to the surface of large-diameter steel pipes are usually cleaned using solvents or emulsions. However, rust, scale, and welding slag on the surface of large-diameter steel pipes cannot be removed and require further treatment.
3. Pickling: Common pickling methods include chemical and electrolytic methods. However, only chemical pickling is used for corrosion protection of large-diameter steel pipes. Chemical pickling achieves the required cleanliness and roughness on the surface of large-diameter steel pipes, facilitating subsequent anchoring lines. It is usually used as a post-treatment after shot blasting (sandblasting).
4. Rust Removal with Tools: For large-diameter steel pipes, oxide scale, rust, and welding slag can be removed by cleaning and polishing the surface with a wire brush. Rust removal with tools is divided into manual and power-operated methods. Manual tools can achieve Sa2 grade rust removal, while power tools can achieve Sa3 grade. If the oxide scale on the surface of large-diameter steel pipes is particularly stubborn, it may not be completely removed even with tools, requiring alternative methods.
Second, what are the connection methods for large-diameter steel pipes?
1. Heat-shrink fittings for large-diameter steel pipes: Pipe connections can be made using on-site welding. When on-site welding is not possible, heat-shrink fittings are used for supplementary sealing. Under heat, they shrink, achieving a shrink seal.
2. Quick-connect flanges for large-diameter steel pipes: The flanges and matching parts are circumferentially argon-arc welded. Quick clamps compress the sealing gasket between the flanges, achieving a tight seal and completing the connection.
3. Large-diameter steel pipe compression type: The piping uses flanged or welded end rings, and the connection method is a union or semi-union. After the rubber sealing ring is compressed by 20%-30% to limit the seal, it enters the metal sealing groove, and the limiting seal protects the sealing element. Suitable for harsh environments such as foundation settlement, high temperature, and high pressure.
4. Large-diameter steel pipe welding type: The fittings and accessories of the usual socket type are circumferentially argon-arc welded to achieve a sealing effect and complete the connection.
5. Large-diameter steel pipe tapered thread type: The external threaded sleeve and accessories are circumferentially argon-arc welded, and the internal threaded fittings are connected with tapered threads to achieve a sealing effect and complete the connection. Suitable for harsh environments such as foundation settlement, high temperature, and high pressure.
6. Large-diameter steel pipe press-fit type: The piping is inserted into the fitting, the two ends of which have protruding U-shaped grooves. The internal sealing ring is pressed into the socket using a special pipe fitting tool for connection.
7. Compression type for large-diameter steel pipes: Insert the pipe into the fitting’s inlet, tighten with a nut, and use a screw force to compress the sleeve at the inlet through the sealing ring, achieving a seal and completing the pipe connection.
Third, what methods can be used to improve the rust resistance of large-diameter steel pipes？
1. When using sandblasting or manual mechanical rust removal, the iron oxide scale on the surface of the large-diameter steel pipe peels off, leaving the metal directly exposed to the air. If a primer is not applied promptly, the surface of the large-diameter steel pipe is prone to re-rusting, affecting the adhesion of the paint film. Since paint is a time-sensitive material, it easily expires and becomes ineffective if stored in stock. Therefore, the main indicators of the paint should be retested before use, and only those that meet the standards are permitted for use.
2. Rust removal: This is an important process before coating large-diameter steel pipes and components, and it is crucial for large-diameter steel pipes. Rust removal improves the adhesion of anti-rust paint, thereby extending the service life of large-diameter steel pipes.
3. After sandblasting, shot blasting, or pickling, the surface of large-diameter steel pipes is cleaner, with less iron oxide scale and rust, improving coating adhesion. When sandblasting or shot blasting is not feasible at the installation site, manual mechanical rust removal can be used, but it is difficult to achieve the required rust removal level.
Post time: Jan-29-2026