Large-caliber industrial pipes are essential components in various industries, including oil and gas, petrochemical, power generation, and water transportation. These pipes are designed to withstand high pressures, extreme temperatures, and corrosive environments. The production process of large-caliber industrial pipes is complex and involves multiple stages, each critical to ensuring the final product meets stringent quality and performance standards. This article provides a detailed overview of the production process, from raw materials to the final delivery of the finished product.

1. Flat Plate

The production process begins with the selection of high-quality flat plates, typically made from carbon steel, stainless steel, or alloy steel. The flat plates are chosen based on the specific requirements of the pipe, such as diameter, wall thickness, and material grade. The plates are inspected for surface defects, dimensional accuracy, and chemical composition to ensure they meet the required specifications.

2. Re-inspection

Before proceeding to the next stage, the flat plates undergo a thorough re-inspection. This step involves verifying the material’s mechanical properties, such as tensile strength, yield strength, and elongation. Additionally, the plates are checked for any surface imperfections, such as cracks, laminations, or inclusions, which could compromise the integrity of the final product.

3. Cutting

Once the flat plates have been inspected and approved, they are cut into the required dimensions. This is typically done using high-precision cutting machines, such as plasma cutters or laser cutters, to ensure accurate and clean cuts. The cutting process is critical, as any deviations from the specified dimensions can affect the subsequent stages of production.

4. Planing

After cutting, the edges of the flat plates are planed to remove any burrs or irregularities. Planing ensures that the edges are smooth and uniform, which is essential for achieving a high-quality weld during the subsequent welding stages. The planing process is typically carried out using edge-planing machines, which provide a consistent and precise finish.

5. Roll Up Pipes

The next stage involves rolling the flat plates into cylindrical shapes. This is done using a plate rolling machine, which applies gradual pressure to bend the plates into the desired curvature. The rolling process is carefully controlled to ensure that the plates are formed into precise cylindrical shapes without any deformations or wrinkles. The diameter and curvature of the rolled plates are continuously monitored to ensure they meet the specified tolerances.

6. Pre-welding

Once the plates have been rolled into cylindrical shapes, the edges are prepared for welding. This involves aligning the edges of the rolled plates and tack welding them together to hold the shape in place. Tack welding is a temporary welding process that ensures the edges remain aligned during the subsequent welding stages. The pre-welding stage is critical, as any misalignment at this stage can lead to defects in the final weld.

7. Welding Seam Cleaning

Before the main welding process begins, the welding seams are thoroughly cleaned to remove any contaminants, such as oil, grease, or rust. Cleaning the seams is essential to ensure a strong and defect-free weld. This is typically done using wire brushes, grinding tools, or chemical cleaning agents, depending on the type of material and the level of contamination.

8. Automatic Welding

The main welding process is carried out using automatic welding machines, which provide consistent and high-quality welds. The welding process typically involves submerged arc welding (SAW) or gas metal arc welding (GMAW), depending on the material and thickness of the pipe. The automatic welding machines are programmed to follow precise welding parameters, such as welding speed, voltage, and current, to ensure a uniform and defect-free weld. The welding process is closely monitored to detect any deviations or defects, which are immediately corrected.

9. X-ray Test

After the welding process is complete, the welded seams undergo non-destructive testing (NDT) to detect any internal defects, such as cracks, porosity, or inclusions. One of the most common NDT methods used in pipe production is X-ray testing. X-ray testing involves passing X-rays through the welded seam and capturing the resulting image on a film or digital detector. The X-ray images are then analyzed by qualified inspectors to identify any defects that may compromise the integrity of the weld. If any defects are detected, the weld is repaired, and the X-ray test is repeated until the weld meets the required quality standards.

10. Degreasing

After the X-ray test, the pipes undergo a degreasing process to remove any residual oil, grease, or other contaminants from the surface. Degreasing is essential to prepare the pipes for subsequent heat treatment processes, such as solution annealing. The degreasing process typically involves using chemical solvents or alkaline cleaning agents, followed by rinsing with water to remove any remaining residues.

11. Solution Annealing

Solution annealing is a heat treatment process that is used to improve the mechanical properties and corrosion resistance of the pipes. The pipes are heated to a specific temperature, typically between 1000°C and 1100°C, depending on the material, and then rapidly cooled. This process helps to dissolve any precipitates or impurities in the material, resulting in a more homogeneous microstructure. Solution annealing also relieves any residual stresses in the material, which can improve the pipe’s performance under high-pressure conditions.

12. Round Off
After solution annealing, the pipes may undergo a rounding-off process to ensure they have a uniform and precise circular shape. This is particularly important for large-caliber pipes, where even minor deviations from the desired shape can affect the pipe’s performance. The rounding-off process is typically carried out using hydraulic or mechanical rounding machines, which apply controlled pressure to the pipe to achieve the desired shape.

13. Straightening

The pipes are then straightened to ensure they have a uniform and straight profile. Straightening is essential for large-caliber pipes, as any curvature or bending can affect the pipe’s ability to withstand high pressures and loads. The straightening process is typically carried out using hydraulic or mechanical straightening machines, which apply controlled pressure to the pipe to remove any bends or curves.

14. End Plain

The ends of the pipes are then machined to ensure they have a smooth and uniform surface. This is important for ensuring a proper fit and seal when the pipes are connected to other components, such as flanges or fittings. The end plain process is typically carried out using lathes or milling machines, which remove any irregularities or imperfections from the pipe ends.

15. Degreasing (Second Time)

After the end plain process, the pipes undergo a second degreasing process to remove any residual oil, grease, or other contaminants that may have been introduced during the machining process. This ensures that the pipes are clean and free from any contaminants that could affect the subsequent pickling process.

16. Pickling

Pickling is a chemical cleaning process that is used to remove any oxides, scale, or other surface impurities from the pipes. The pipes are immersed in a pickling solution, typically consisting of hydrochloric acid or sulfuric acid, which dissolves the surface impurities. After pickling, the pipes are thoroughly rinsed with water to remove any residual acid. Pickling is essential for improving the surface quality of the pipes and preparing them for the final surface treatment processes.

17. Hydraulic Test

The pipes are then subjected to a hydraulic test to verify their ability to withstand high pressures. The hydraulic test involves filling the pipes with water and applying a pressure that is significantly higher than the pipe’s design pressure. The pipes are held at this pressure for a specified period, during which they are inspected for any leaks, deformations, or other signs of failure. The hydraulic test is a critical quality control step, as it ensures that the pipes can safely operate under the intended pressure conditions.

18. Inspection for Finished Products

After the hydraulic test, the pipes undergo a final inspection to verify that they meet all the required quality and performance standards. This involves a thorough visual inspection, as well as dimensional checks, surface quality checks, and verification of the pipe’s mechanical properties. Any pipes that do not meet the required standards are either repaired or rejected. The final inspection is a critical step in ensuring that only high-quality pipes are delivered to the customer.

19. Marking

Once the pipes have passed the final inspection, they are marked with the necessary information, such as the pipe’s material grade, size, wall thickness, and heat number. The marking is typically done using stencils, stamps, or laser marking machines. The marking process is important for traceability, as it allows the pipes to be identified and tracked throughout their service life.

20. Warehouse Entry of Finished Products

After marking, the finished pipes are transported to the warehouse, where they are stored until they are ready for shipment. The pipes are typically stored in a controlled environment to protect them from corrosion, contamination, or damage. The warehouse is equipped with handling equipment, such as cranes and forklifts, to facilitate the movement and storage of the pipes.

21. Packing

Before shipment, the pipes are packed to protect them from damage during transportation. The packing process typically involves wrapping the pipes in protective materials, such as plastic or paper, and securing them with straps or bands. The pipes may also be placed in wooden crates or containers for additional protection. The packing process is important for ensuring that the pipes arrive at their destination in good condition.

22. Delivery
The final stage of the production process is the delivery of the finished pipes to the customer. The pipes are transported using trucks, trains, or ships, depending on the distance and destination. The delivery process is carefully planned to ensure that the pipes arrive on time and in good condition. Upon arrival, the pipes are inspected by the customer to verify that they meet the required specifications and quality standards.

Conclusion

The production of large-caliber industrial pipes is a complex and highly controlled process that involves multiple stages, each critical to ensuring the final product meets the required quality and performance standards. From the selection of raw materials to the final delivery of the finished product, every step in the production process is carefully monitored and controlled to ensure that the pipes can withstand the demanding conditions they will encounter in service. By following this rigorous production process, manufacturers can produce high-quality large-caliber industrial pipes that meet the needs of a wide range of industries.