4 welded steel tube connection methods

Welded steel pipes are fabricated by rolling steel plates and welding them along a mold of a specified diameter. These pipes are widely utilized in industries such as construction, machinery manufacturing, and bridge engineering due to their high production efficiency, rigidity, and pressure resistance, especially in larger sizes. Welded pipes are generally categorized into carbon steel pipes and stainless steel pipes.

Connection Methods for Welded Steel Tubing

1. Threaded Connection

Threaded connections link pipes, fittings, and valves through internal and external threads. This method is commonly used for threaded equipment, accessories, and in situations requiring frequent disassembly where fire is not permitted.

- Galvanized Welded Steel Pipes for Low-Pressure Fluids: Suitable for nominal diameters below 150mm and working pressures below 1.6MPa.

- Water Supply Pipes: Working pressure should not exceed 1.6MPa, with a maximum nominal diameter of 150mm.

- Hot Water Pipes: Suitable for working pressures up to 0.2MPa and a maximum nominal diameter of 50mm.

- Thin-Walled Stainless Steel Welded Pipes: Suitable for connecting pipe sections from DN65 to DN100.

When connecting threaded welded pipes, appropriate packing is placed between the external and internal threads of the pipe or valve to ensure sealing, protect the pipe opening, and facilitate disassembly. The main features of threaded connections include ease of installation and disassembly, simple construction, and low pressure resistance. The main installation steps are pipe breaking, threading, assembling pipe fittings, and straightening pipe sections.

2. Flange Connection

Flange connections are often used for temporary drainage and irrigation pipelines, pump station pipe-fitting combinations, welded steel pipes, valves, and accessories. Flanges can be made of various materials, including cast iron, steel, plastic, non-ferrous metals, glass, and fiberglass.

Flange Selection: Based on the medium's nature, pressure, and temperature, ensuring the nominal pressure meets design requirements. For connecting welded pipe sections or flange valves, the appropriate method should be selected according to design requirements and working pressure.

Flange Types: Equipment flanges are generally concave or grooved, so the selected flange should be convex or tenon. Thin-walled stainless steel welded pipes are suitable for pipe sections above DN100.

Flange connections are characterized by easy disassembly, high strength, good sealing performance, and the ability to withstand large pressures. When installing flanges, they must be kept parallel, and the sealing surfaces must be clean and undamaged. The gasket should be selected according to design requirements.

3. Welding Connection

Welding is a common method for connecting welded steel pipes, involving heating the pipe interface and welding rod, then joining and securing the weldments. This method offers firm welding, good sealing, durability, low cost, and minimal maintenance requirements.

Welding Methods: Include gas welding, arc welding (automatic spot welding, manual electric welding), resistance welding, manual arc welding, manual argon arc welding, submerged arc automatic welding, and contact welding.

Example: ERW (Electric Resistance Welding) pipes use resistance heat generated by current passing through the weldment to locally heat and pressurize it, requiring no filler metal, allowing high productivity, minimal deformation, and easy automation.

4. Grooved Clamp Connection

The grooved clamp connection is a modern method for connecting welded pipes, offering numerous advantages. It works by using the cooperation of the clamp and the groove, compressing the pipe through bolt tightening to achieve a sealed connection.

Components: Typically include clamps, slots, seals, and flanges. Clamps are usually made of gray cast iron, ductile iron, or stainless steel, while the clamping groove and sealing plate are often round or square. Flanges are used to withstand the pressure in the welded pipe.

Conclusion

Welded steel pipes are versatile and essential in many industries. By understanding and utilizing the appropriate connection methods—threaded, flange, welding, and grooved clamp connections—users can ensure the efficiency, safety, and reliability of their welded steel pipe installations.