Cleaning methods of large-diameter steel pipes:
1. Shot blasting and rust removal: The blades are driven to rotate at high speed by a high-power motor, so that steel sand, steel shot, wire segments, minerals, and other abrasives are sprayed on the surface of the steel pipe under the action of centrifugal force. On the one hand, rust, oxides, and dirt are removed, and on the other hand, the steel pipe is subjected to the violent impact and friction of the abrasive to achieve the required uniform roughness.
2. Cleaning: Grease, dust, lubricants, and organic matter adhered to the surface of large-diameter steel pipes are usually cleaned with solvents and emulsions. However, the rust, scale, and welding slag on the surface of the steel pipe cannot be removed, and other treatment methods are required.
3. Pickling: Common pickling methods include chemical and electrolytic methods. However, chemical pickling is only used for pipeline anti-corrosion. Chemical pickling can achieve the cleanliness and roughness of the surface of large-diameter steel pipes, which is convenient for subsequent anchor lines. Usually used as a reprocessing after shot blasting (sand).
4. Tool rust removal: The surface oxide scale, rust, and welding slag of large-diameter steel pipes can be cleaned and polished with a wire brush. Tool rust removal is divided into manual and power. Manual tool rust removal can reach the Sa2 level, and power tool rust removal can reach the Sa3 level. If the surface of the steel pipe is attached to a particularly strong oxide scale, it may not be cleaned with the help of tool rust removal, and other methods need to be found.
Connection methods of large-diameter steel pipes:
1. Heat shrink fittings for large-diameter steel pipes: When connecting pipelines, on-site welding can be used. If the welding points cannot be handled on the construction site, heat shrink fittings are used for supplementary sealing, which shrinks under the action of heat to achieve shrinkage sealing.
2. Large-diameter steel pipe quick-connect flange type: Perform annular argon arc welding on the flange and the matching, and use quick clamps to compress the sealing gasket between the flanges to play a sealing role and complete the matching connection.
3. Large-diameter steel pipe limited compression type: The piping adopts a flanging or port welding ring, and the connection method is a flexible or semi-flexible connection. After the rubber sealing ring is limited and sealed by 20%-30%, it enters the metal sealing groove, and a limited seal is used to protect the sealing element. It can be used in harsh environments such as foundation sinking, high temperatures, and high pressure.
4. Large-diameter steel pipe welding type: The usual socket-type pipe fittings and matching are subjected to annular argon arc welding to play a sealing role and complete the matching connection.
5. Large-diameter steel pipe tapered thread type: The external thread sleeve is subjected to annular argon arc welding with matching, and the internal threaded pipe fittings are connected with a tapered pattern to play a sealing role and complete the matching connection. It can be used in harsh environments such as foundation sinking, high temperatures, and high pressure.
6. Large-diameter steel pipe clamping type: Insert the piping into the pipe fitting, and the two ends of the pipe fitting are protruding U-shaped grooves. The built-in sealing ring is connected by clamping the socket part with a special pipe fitting tool.
7. Compression type: insert the pipe into the pipe mouth of the pipe fitting, tighten it with a nut, and use spiral force to compress the sleeve of the pipe mouth through the sealing ring to seal and complete the pipe connection.
Methods to improve the rust resistance of large-diameter steel pipes:
1. When using sandblasting or manual mechanical rust removal, due to the shedding of the oxide scale on the large-diameter steel pipe, the metal on the surface of the large-diameter steel pipe is directly exposed to the air. If a primer is not applied in time, the surface of the large-diameter steel pipe is prone to rust again, affecting the adhesion of the paint film. Since paint is a time-sensitive material, it is easy to expire and fail due to inventory backlog. Therefore, the main indicators of the paint must be re-tested before use, and the results must meet the standards before use.
2. Rust removal: This is an important process before coating large-diameter steel pipes and components, and it is the key to large-diameter steel pipes. Rust removal can improve 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 clean of iron oxide scale and rust, which improves the adhesion of the coating. When the installation site cannot use sandblasting or shot blasting, manual mechanical rust removal can be used to achieve the rust removal level.
Post time: Jan-07-2025