Large diameter steel pipe connection method and cleaning method

Cleaning method of large diameter steel pipe:
1. Shot blasting and rust removal: The high-power motor drives the blades to rotate at a high speed so that abrasives such as steel sand, steel shot, wire segments, and minerals are sprayed and blasted on the surface of the steel pipe under the action of centrifugal force. On the one hand, rust, oxides and Dirt, on the other hand, the steel pipe achieves the required uniform roughness under the action of the abrasive impact and friction.
2. Cleaning: grease, dust, lubricant and organic matter adhering to the surface of large-diameter steel pipes are usually cleaned with solvents and emulsions. However, the rust, oxide 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, the anticorrosion of the pipeline only adopts chemical pickling. Chemical pickling can achieve the cleanliness and roughness of the surface of large-diameter steel pipes, which is convenient for subsequent anchor lines. Usually as a reprocessing after shot peening (sand).
4. Derusting of tools: For the surface oxide scale, rust and welding slag of large-diameter steel pipes, wire brushes can be used to clean and polish the surface. The rust removal of tools is divided into two types: manual and power. The rust removal of manual tools can reach Sa2 level, and the rust removal of power tools can reach Sa3 level. If there is a particularly strong oxide scale attached to the surface of the steel pipe, it may not be able to be cleaned with the help of tools to remove rust, and other methods need to be found.

Large diameter steel pipe connection method:
1. Heat-shrinkable fittings for large-diameter steel pipes: On-site welding can be used when connecting pipes. The welding point cannot be processed on the construction site, and heat-shrinkable pipe 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: Ring-shaped argon arc welding is performed on the flange and the matching, and the gasket between the flanges is compressed by the quick clamp, which plays a sealing role and completes the matching connection.
3. Limit compression type of large-diameter steel pipe: the piping adopts flanging or port welding ring, and the connection method is union or semi- union connection. After the limit seal of the rubber sealing ring is compressed by 20%-30%, it enters the metal sealing groove. A limit seal is used to protect the sealing element. It can be used in harsh environments such as foundation subsidence, high temperature and high pressure.
4. Large-diameter steel pipe welding type: Ring-shaped argon arc welding is performed on the usual socket-type pipe fittings and matching, which plays a sealing role and completes the matching connection.
5. Large-diameter steel pipe taper thread type: The outer threaded sleeve and the matching are subjected to annular argon arc welding, and the inner threaded pipe fittings are connected with a tapered thread to play a sealing role to complete the matching connection. It can be used in harsh environments such as foundation subsidence, high temperature and high pressure.
6. Compression type of large-diameter steel pipe: insert the pipe into the pipe fitting, the two ends of the pipe fitting are protruding U-shaped grooves, and the built-in sealing ring is connected by pressing the socket part of the special pipe fitting tool.
7. Compression type: Insert the pipe into the nozzle of the pipe fitting, fasten it with a nut, and compress the casing of the nozzle through the sealing ring with a screw force, which plays a sealing role and completes the pipe connection.

Methods to improve the rust resistance of large-diameter steel pipes:
1. When sandblasting or manual mechanical rust removal is used, due to the peeling off of the oxide scale of the large-diameter steel pipe, the metal on the surface of the large-diameter steel pipe is directly exposed to the air. Rust, affecting the adhesion of the paint film. Since the paint is an aging material, the inventory backlog is easy to expire and become invalid. Therefore, the main indicators of the paint are re-inspected before use, and the results can only be used if they meet the standards.
2. Derusting: This is an important process before coating of large-diameter steel pipes and components, and is the key to large-diameter steel pipes. Rust removal can improve the adhesion of anti-rust paint, thereby prolonging the service life of large-diameter steel pipes.
3. The surface of the large-diameter steel pipe treated by sandblasting, shot blasting or pickling is relatively clean, such as iron oxide scale and rust, which improves the adhesion of the coating. When the installation site is unconditionally treated by sandblasting and shot blasting, manual and mechanical rust removal can be used, but the rust removal level is reached.