Shell Support and Manufacturing in Pressure Vessel Production

In the production of pressure vessels, key processes such as shell support and preheating play a vital role, especially during the manufacturing of large-scale equipment. The support for the shell, hole-making, welding preheating, and transport handling directly impact the quality of the pressure vessel and its operational lifespan. This article provides an in-depth discussion of these processes, helping to better understand their practical applications in production.

Shell and Skirt Support

The primary purpose of shell support is to prevent deformation during the manufacturing process. Large and oversized pressure vessels, after the shell is rolled, welded, and roundness is adjusted, typically require internal and external supports to prevent distortion. Common types of supports include straight-line, cross-shaped, and crisscross supports, which help to distribute external forces and reduce stress concentration, maintaining the integrity of the vessel structure.
These supports are essential not only during the production phase but also during transport, ensuring that the shell does not deform under its own weight or the lifting forces. During lifting and transportation, the vessel's weight combined with the pulling force from the lifting equipment can cause deformation. Therefore, supports must be installed on the inside or edges of the shell to preserve its shape. Additionally, during the shell assembly phase, because of the large diameter and thin outer walls, using roller frames to rotate the shell can cause deformation from the combined weight of the shell and the rotational force of the rollers. In such cases, internal supports are necessary to maintain the vessel's shape.

Shell Hole Support

In the production of pressure vessels, especially large, thin-walled containers, a large number of nozzle holes must be drilled. The manufacturing process for towers and similar equipment is complex, and these vessels require numerous holes. However, due to the large diameter and thin walls of the shell, cutting the holes can cause minor deformation. During nozzle installation, the weight of the nozzle and the heat from welding can further exacerbate local deformations around the hole, potentially causing collapse or distortion, affecting installation accuracy.
To address this issue, specialized support tools are used at the hole edges. These supports prevent deformation during the hole-making and nozzle installation processes, ensuring that the equipment can be assembled smoothly and meet design specifications.

Preheating of Thick-Walled Shells

In the welding process of thick-walled pressure vessels, preheating is essential to ensure welding quality and prevent cracks. Especially before performing root pass welding, it is critical to preheat the weld area. Preheating prevents cracks caused by large temperature differences, especially in environments with high thermal gradients.
Preheating tools typically consist of inlet pipes, heating pipes, burners, connecting pipes, and brackets. By adjusting the configuration of these components, the heating area and temperature can be optimized based on the specific welding requirements. In practice, the heating pipes are bent to fit the vessel's diameter and are sealed at both ends. Burners, powered by natural gas or other fuels, heat the pipes to the desired temperature. To improve heating efficiency, the burners are designed with openings on both sides to increase heat transfer.

Lifting and Turning of Pressure Vessels

Lifting, transporting, and turning pressure vessels are essential steps in the manufacturing process. Traditionally, steel wire ropes or simple lifting lugs are used to connect the vessel to the crane. However, these methods pose risks such as limited load-bearing capacity, wear and tear, and unpredictable fatigue, which can result in accidents like wire rope breakage or the vessel slipping off.
To address these issues, modern lifting systems use a combination of pulleys and wire ropes to enhance the grip of the lifting lugs on the vessel's inner walls, improving stability during lifting. Precision-designed molds ensure that the lifting equipment is securely fixed to the shell, allowing for safer and more efficient lifting and turning operations.

Overall Straightness Inspection Tools

After the manufacturing of pressure vessels, straightness inspection is a critical step to ensure the vessel's proper functioning. Given the large size of pressure vessels, especially tower-type equipment, traditional methods of checking straightness are impractical, and manual measurements often lack precision. Therefore, using specialized tools for straightness inspection is a more efficient and reliable solution.
The overall straightness inspection tool typically consists of angle steel, fine steel wires, and fine lines. The angle steel is welded onto the center nozzle of the head, and fine steel wires are fixed to maintain stability. A fine line is then hung vertically from the same side of the vessel to check the distance between the line and the steel wire. This method provides both high precision and efficiency in straightness inspection.

Conclusion

The manufacturing of pressure vessels involves several critical steps, each requiring specific tools to ensure high efficiency and safety. Properly designed supports, preheating tools, and inspection devices not only improve manufacturing precision but also reduce deformation, ensure weld quality, and guarantee that the equipment meets performance requirements. The advancement of these technologies provides the pressure vessel industry with more reliable and efficient solutions, driving technological progress and enhancing safety standards across the entire sector.