A pressure vessel design basis fixes the numbers every calculation depends on: design pressure and temperature, minimum design metal temperature, materials and corrosion allowance, external loads, and the governing code. Get those right and the calculations, drawings and inspection all follow; get them wrong and the vessel is redesigned later.
Key Takeaways
- Design conditions come from the process, with margins agreed up front.
- Corrosion allowance and material choice drive thickness and cost.
- Nozzle and external loads need to be known, not assumed.
- FEA is for cases the code rules don't cover.
Design Pressure and Temperature
Design conditions should come from the process data with an agreed margin over the maximum operating case, including upset conditions. The minimum design metal temperature matters as much as the maximum, because it governs material toughness requirements.
Materials and Corrosion Allowance
Material selection follows the fluid, temperature and cost. The corrosion allowance adds directly to wall thickness, so it should reflect expected Service life rather than habit.
Loads Beyond Pressure
Wind, seismic, weight of contents, nozzle loads from connected piping and support reactions all act on the vessel. Pipe stress results from CAESAR II give real nozzle loads instead of guesses.
Calculations and Checks
We carry out the code calculations in PV Elite and COMPRESS. Where a nozzle load or support falls outside the code's design rules, local stresses are checked by finite element analysis in ANSYS.
From Design to Inspection
The design basis, calculations and drawings give the fabricator and inspector the same reference, which makes hydrotest and acceptance straightforward.
Frequently Asked Questions
Which code do you use?
The code your Project specifies. Pressure vessels are commonly designed to ASME Section VIII.
Can you review a vendor's vessel design?
Yes. As Owner's Engineer we review vendor calculations and drawings before fabrication.
