Large diameter steel pipe connection methods and cleaning methods

Cleaning methods for large diameter steel pipes:
1. Shot blasting and rust removal: A high-power motor drives the blades to rotate at high speed, so that steel sand, steel shots, wire segments, minerals and other abrasives 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 reaches the required uniform roughness under the action of the violent impact of abrasives and friction.
2. Cleaning: To remove grease, dust, lubricants, and organic matter adhered to the surface of large-diameter steel pipes, solvents and emulsions are usually used to clean the surface. However, the rust, oxide scale, and welding slag on the surface of the steel pipe cannot be removed, and other treatment methods are needed.
3. Pickling: Common pickling methods include chemical and electrolysis. However, only chemical pickling is used for anti-corrosion of pipelines. Chemical pickling can achieve the highest cleanliness and roughness on the surface of large-diameter steel pipes, which facilitates subsequent anchor lines. Usually used as post-processing after shot blasting (sand).
4. Tool rust removal: To remove oxide scale, rust, and welding slag on the surface of large-diameter steel pipes, a wire brush can be used to clean and polish the surface. There are two types of tool rust removal: 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 particularly strong oxide scale attached to the surface of the steel pipe, it may not be possible to remove the rust even with the help of tools, so other methods need to be found.

Large diameter steel pipe connection method:
1. Large-diameter steel pipe heat-shrinkable fittings: When connecting pipes, on-site welding can be used. Welding joints cannot be processed at the construction site, so heat-shrinkable pipe fittings are used for supplementary sealing. They shrink 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 matching parts, and use a quick clamp to compress the sealing gasket between the flanges to act as a seal and complete the matching connection.
3. Large-diameter steel pipe limit compression type: The pipe adopts flange or port welding ring, and the connection method is a union or semi-union connection. After the rubber sealing ring limit seal 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 sinking, 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 supporting parts to act as a seal and complete the matching connection.
5. Large-diameter steel pipe taper thread type: perform annular argon arc welding on the external thread sleeve and supporting parts, and the internal threaded pipe fittings are connected with tapered threads for sealing to complete the supporting connection. It can be used in harsh environments such as foundation sinking, high temperature and high pressure.
6. Clamping type of large-diameter steel pipe: Insert the pipe into the pipe fitting. Both ends of the pipe fitting are protruding U-shaped grooves. The built-in sealing ring is connected by clamping with the socket part of the special pipe fitting tool.
7. Compression type: Insert the pipe into the nozzle of the pipe fitting, tighten it with a nut, and use spiral force to compress the casing at the nozzle through the sealing ring to act as a seal and complete the pipe connection.

Methods to improve the rust resistance of large-diameter steel pipes:
1. When sandblasting or manual mechanical rust removal is used, the oxide scale on the large-diameter steel pipe falls off, and the metal on the surface of the large-diameter steel pipe is directly exposed in the air. If a primer is not applied in time, the surface of the large-diameter steel pipe will be easily re-painted. Rust affects the adhesion of the paint film. Since paint is a time-sensitive material and the inventory is easily expired, the main indicators of the paint should be re-inspected before use. 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 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. The surface of large-diameter steel pipes that have been treated by sandblasting, shot blasting or pickling processes will be relatively clean of oxide scale and rust, which improves the coating adhesion. When the installation site is unconditionally treated by sand blasting and shot blasting, manual mechanical rust removal can be used to achieve the rust removal level.