KEVOS® MAKEOS · Strength
Pressure Vessel Shell and Head Thickness Comparison
What wall thickness does this vessel shell need, and how do hemispherical, ellipsoidal and torispherical heads compare?
Required thickness of a cylindrical shell under internal pressure and of hemispherical, 2:1 ellipsoidal and torispherical heads by the widely used ASME Section VIII Division 1 formulas, with joint efficiency and corrosion allowance, compared side by side, plus the hydrostatic test pressure — for preliminary comparison only.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Design pressure | MPa | Internal design pressure. |
| Inside diameter | mm | Inside diameter of the shell. |
| Allowable stress at design temperature | MPa | Allowable tensile stress of the plate at design temperature (from the code’s material tables). |
| Joint efficiency | Weld joint efficiency for the radiography extent (1.0 full, 0.85 spot, 0.7 none for butt welds). | |
| Corrosion allowance | mm | Corrosion allowance added to the calculated thickness. |
| Hydrotest factor | Hydrostatic test pressure as a multiple of design pressure (code-dependent; also adjusted by the stress ratio). |
Method and formulas
- Cylinder (circumferential stress): t = p R ÷ (S E − 0.6p) + CA.
- Hemispherical head: t = p R ÷ (2 S E − 0.2p) + CA.
- 2:1 ellipsoidal head: t = p D ÷ (2 S E − 0.2p) + CA.
- Torispherical head (crown radius = D, knuckle 6% D): t = 0.885 p L ÷ (S E − 0.1p) + CA.
- Example: 1 MPa in a 1000 mm shell needs 5.7845 mm; a 2:1 head needs 5.7662 mm.
Limitations
- Preliminary comparison only; pressure vessels must be designed, fabricated, inspected and certified to the applicable code (AS 1210, ASME VIII, EN 13445).
- External pressure, nozzles, supports and local loads are not covered.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Compare head types for weight and cost
- Estimate plate thickness before detailed design
- Check a vessel’s nominal wall against its pressure
Who it is for
- Mechanical engineers
- Process engineers
- Estimators
What you get
- Shell thickness
- Head thickness for three types
- Hydrostatic test pressure
Interpreting the result
- Hemispherical heads are thinnest but cost most to form; torispherical heads are cheapest but thickest.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 290–294. Topic reference; no source tables or recommended settings are reproduced.
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Open the Pressure Vessel Shell and Head Thickness Comparison calculator
