Pressure Vessel Stress Calculator
Calculate hoop and axial stress in a thin-walled cylindrical pressure vessel from internal pressure, diameter, and wall thickness.
Hoop (Circumferential) Stress
250.00 MPa
Hoop (Circumferential) Stress vs Internal Pressure (P)
Formule
## Thin-Walled Pressure Vessel Stresses For a cylindrical vessel where the wall thickness is much less than the diameter (D/t > 10), the stresses can be calculated using simplified thin-wall formulas. ### Formulas **Hoop stress: sigma_h = P × r / t** (circumferential, the larger stress) **Axial stress: sigma_a = P × r / (2t)** (longitudinal, half the hoop stress) The hoop stress is twice the axial stress, which is why pressure vessels fail along longitudinal seams (circumferential stress governs).
Exemple Résolu
A vessel with 1000 mm diameter, 10 mm wall, at 5 MPa pressure.
- 01r = 1000 / 2 = 500 mm
- 02Hoop stress = 5 × 500 / 10 = 250 MPa
- 03Axial stress = 5 × 500 / (2 × 10) = 125 MPa
- 04D/t = 100 (thin-wall assumption valid)
Questions Fréquentes
When is the thin-wall assumption valid?
The thin-wall formulas are accurate when D/t > 10 (some sources say > 20). For thicker walls, thick-wall (Lame) equations are needed, which account for stress variation through the wall thickness.
Why is hoop stress twice axial stress?
A cylindrical vessel must resist pressure on a larger projected area in the circumferential direction than the longitudinal. The force balance on a longitudinal slice yields twice the stress of a transverse slice.
How do codes like ASME size vessels?
ASME BPVC Section VIII uses modified versions of these formulas with allowable stress, joint efficiency, and corrosion allowance: t = P*R / (S*E - 0.6*P) + C.A., where S is allowable stress and E is joint efficiency.
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