The difference between Division 1 and Division 2, and what documents a client should ask for.
Two design paths, two levels of documentation
Division 1 is a set of formula-based design rules and is sufficient for most industrial vessels. Division 2 allows a higher design pressure and less thickness through more detailed stress analysis, but also demands stricter documentation, welding, and inspection.
Whichever path is chosen, the client should receive the calculation report, an approved fabrication drawing, welders' WPS/PQR records, radiography films, and the hydrostatic test report as part of the vessel's technical file.
Division 1 vs Division 2 at a glance
| Feature | Division 1 | Division 2 |
|---|---|---|
| Calculation method | Simple code formulas | Detailed stress analysis |
| Safety factor | More conservative | Lower, less thickness |
| Design pressure covered | Moderate | Higher |
| Documentation & inspection | Standard | Stricter |
Division 2 usually pays off when the resulting weight and thickness savings are significant at scale or at high design pressure; otherwise Division 1's simplicity is enough for most industrial projects.
