What are the manufacturing processes for pressure vessels?

I. Main Manufacturing Processes

1. Raw Material Acceptance and Pre-treatment

After the steel arrives at the site, it needs to undergo material re-inspection to confirm that its chemical composition and mechanical properties meet the design requirements.

Pre-treatment includes cleaning (rust removal, degreasing), straightening (correcting transportation deformation), and applying a protective primer to improve the material's corrosion resistance and subsequent processing accuracy.

2. Marking and Blanking

Marking is the first manufacturing process and directly affects the dimensional accuracy of the parts. The blank dimensions need to be calculated based on the unfolded drawing, and blanking lines, processing lines, and inspection lines need to be marked.

Blanking methods include mechanical cutting (such as shearing machines) and thermal cutting (such as flame cutting, plasma cutting). CNC cutting can improve accuracy and reduce material waste.

3. Beveling

To ensure welding quality, the edges of the plates need to be beveled. Common methods include edge planing or flame cutting followed by finishing.

4. Forming Process

Cylinder Forming: Steel plates are typically rolled into cylindrical shapes using a plate rolling machine, controlling ovality and edge angles.

Head Forming: Common methods include:
Stamping: Suitable for mass-produced standard heads;
Spinning: Suitable for single-piece or large-diameter heads;
Segmented Forming: Used for ultra-large heads, where segments are pressed and then welded together.

When forming special materials such as zirconium, if the temperature is below 500℃ and the deformation rate is greater than 3%, annealing is required to relieve stress.

5. Assembly and Welding

The assembly sequence is generally as follows: first, longitudinal seam welding; then, circumferential seam butt welding; finally, manholes, connecting pipes, and other accessories are installed.

Welding methods are selected based on material, structure, and working conditions, and mainly include:

Shielded Metal Arc Welding (SMAW): Flexible operation, suitable for on-site construction;

Submerged Arc Welding (SAW): High degree of automation, stable weld quality, suitable for flat welding positions;

Gas Shielded Welding: Such as TIG welding and MIG/MAG welding, protecting the molten pool from air contamination, suitable for stainless steel, non-ferrous metals, etc.

Welding must be performed according to the welding process card to ensure that parameters (current, voltage, number of layers, etc.) are controlled.

6. Non-Destructive Testing

Post-weld testing requires 100% non-destructive testing of the weld. Common methods include radiographic testing (RT), ultrasonic testing (UT), magnetic particle testing (MT), and penetrant testing (PT) to detect internal or surface defects.

7. Heat Treatment

The purpose is to eliminate residual welding stress and improve microstructure and properties. Common methods include overall annealing and localized heat treatment, especially suitable for thick-walled containers or high-strength steel containers.

8. Pressure Testing and Final Inspection

This includes pressure testing (hydraulic or pneumatic) and airtightness testing to verify the container's strength and sealing performance.

After passing the tests, surface anti-corrosion treatment (such as painting or plating) is performed, followed by final inspection and warehousing.

II. Special Manufacturing Technologies (Applicable to Specific Scenarios)

1. Multi-layer Wrapped Containers: Thin steel plates are wound or wrapped layer by layer to avoid deep welds, improving safety. Commonly used in the fertilizer and chemical industries.

2. Wound Containers: Special cross-section steel strips are prestressed and wound around the inner cylinder, eliminating longitudinal welds and improving fatigue life.

3. Fiber-wound Composite Containers: Used for low-temperature or lightweight applications, these containers use carbon fiber/glass fiber composite materials, precisely wound and cured to achieve excellent pressure resistance and sealing performance.