Seamless tubes and pipes have utility in many applications. Manufacturers specializing in this field produce tubes ranging from one inch in diameter to finer than a human hair. Now, this can have a continuous length that can exceed a mile. Seamless pipes are basically utilized in gas, steam, and liquid flow in harsh environments.
Manufacturing process
Typically, the manufacturing process includes extruding, gun drilling, or piercing. However, the extrusion process involves the most uniform outer diameter or OD and a concentric inner diameter or ID. However, extrusion is the only process that is suitable for long-length seamless steel coil tubing. Here the raw materials begin in the form of hot extruded seamless tubes and pipes.
After reaching a heat point, manufacturers cool down the pipes. Additionally, they process the raw material through tube reducers, which are generally termed Pilger mills. The mills help in making the tube straight. Cold Pilger involves maintaining uniform ODs and concentric IDs. A longitudinal cold-rolling process reduces steel tubes’ diameter and wall thickness in a single operation.
The addition of lubricants is an integral part of the OD and ID. Moreover, it is degreased in preparation for annealing. The process typically produces lengths from around 40 feet to 160 feet once manufacturers reduce the lubrication to start the process.
Drawing types
Here seamless tubes and pipes manufacturers differentiate two primary drawing operations.
Floating plug
Floating plug drawing is pulling the tubing through a conical die. Meanwhile, the process produces a more consistent, smoother product that can only be based on relatively light wall products.
Sink drawing
The process of sink drawing is when pipe fabricators pull the tubing through a conical die, and they determine the resulting ID and wall thickness based on the drawing and tubing parameters. They use the process when clients need a heavy relative wall thickness for high-pressure applications. Next, seamless tubes and pipe manufacturers include an ID that’s rougher compared to a floating plug drawing.
Vacuum annealing
Seamless tube fabricators generally anneal long straight lengths and coils after cold reduction to remove internal stresses and restore the material’s crystalline structure. It further initiates cold working.
The rapid cooling of the annealing process transforms the cold-worked, brittle, and rigid material into ductile again.
Hydrotest
Once pipe fabricators fully form the tubes to the desired specification, the producers of seamless tubes and pipes comprehensively test them hydrostatically. Testing determines and verifies that the lines meet the specification or the standard operating procedure. One can obtain several types of information through the verification process. Data that users can explore when choosing the products include
- Material flaws
- Mechanical properties
- Hard spots that can fail when hydrogen is present
Final Product
Once manufacturers have completed all the processes, the final products are ready to be stenciled and delivered to clients. The pipe producers use a level twisting method to coil the seamless tubing on spools for shipment. Or else, they can straighten and cut the tubes to the customers’ specific lengths. In addition, pipe manufacturers further polish the seamless pipes and tubes to give them a sheen and a smooth surface. Also, this is when manufacturers stencil their products for traceability and manufacturing identification.
Conclusion
Manufacturers generally produce seamless tubes and pipes that apply to ASTM standards. Also, manufacturers need to thoroughly test for potential defects before being shipped to the customers. Manufacturers must follow the production process in the proper manner to ensure that the pipes are high in quality and can sustain testing environments.
