Pressure vessels used in industry are leak-tight pressure containers, usually cylindrical or spherical in shape, with different head configurations. They are usually made from carbon or stainless steel and assembled (most) by welding.
Dimensioning of a Pressure Vessel
To design (wall thickness etc.) a pressure vessel, a design engineer should first gather data around parameters that affect pressure vessel performance. These include the vessel’s purpose, its location’s size, shape, and orientation, the type of vessel head to be used, the construction materials to be used, the interior fittings, and the operating circumstances, such as the temperature and pressure of the surrounding environment, as well as process materials and services (deposits and corrosion).
There are essentially three methods available to the design engineer for this purpose:
- Design by Rule (DBR) / Design by Formular (DBF)
- Design by Analysis (DBA)
- Design by Experiment (DBE)
Design by Rule (DBR): ASME BPVC Section VIII Div. 2
Design by Formula (DBF): EN 13445-3
This is a less comprehensive design method contained in known rules and regulations like EN 13445-3, ASME BPVC Section VIII Div. 1, PD 5500, AD 2000, JIS B 8265, and CSA B51. It is a conservative method used by engineers to size pressure vessels in accordance with their application requirements and bases its calculation on normal stress energy. This means that, the pressure vessels designed by ASME BPVC Section VIII Div. 1, give less allowable working pressure as compared to ASME BPVC Section VIII Div. 2. It outlines guidelines for designing pressure vessels with the help of closed-form equations and other stringent regulations. The Design by Rule approach yields pressure vessels that can withstand common failure modes.
Design by Analysis (DBA)
This method requires more detailed calculations than DBA and seeks to protect pressure vessels against 5 types of failure: collapse from buckling, local failure, plastic collapse, cyclic service: fatigue and ratcheting. Seeing that it focuses on maximum distortion energy, it yields pressure vessels that can tolerate greater strains, though comes with an additional cost.
The design by analysis method offers guidelines for designing pressure vessels using numerical analysis (usually finite element analysis).
EN 13445-3 contains regulations for Design by Analysis (DBA) in
- Annex B (Direct Route)
- Annex C (Method based on stress categories)
- Annex T (Design by Experimental Method)
EN 13445-3 also allows a combination of design method.
ASME BPVC Section VIII, Division 2, Part 5 is a methodical approach for demonstrating the adequacy of a pressure vessel component design. ASME BPVC Section VIII Div. 2 Part 5 focuses on design-by-analysis method. It provides detailed rules for performing analyses. The entire approach of this Code based on the philosophy of Protection Against Failure Modes.
Read More
The EN 13445 series comprises European standard for unfired pressure vessel
Shell-and-tube heat exchangers: Applicable Codes and Standards
