Model shell stability under uniform external pressure. Enter diameter, thickness, modulus, yield strength, and length. See results, charts, exports, and examples in one place.
This calculator uses a classical thin cylindrical shell screening model for uniform external pressure. It is useful for quick estimates and early design studies.
teff = tnominal − c
Where c is corrosion allowance.
pelastic = η × k × [2E / √(3(1 − ν²))] × (teff / D)³
Here η is the imperfection factor and k is the end-condition factor.
pyield = 2Sy teff / D
This comes from the thin-wall hoop stress relation under external pressure.
pgoverning = min(pelastic, pyield)
pallowable = pgoverning / SF
Important: This is an engineering estimate, not a substitute for a code-based design check such as detailed vessel or shell standards.
This example is only for illustration and shows a typical thin-shell screening case.
| Diameter | Thickness | Length | Modulus | Poisson’s Ratio | Yield Strength | Imperfection | Safety Factor | Approx. Allowable Pressure |
|---|---|---|---|---|---|---|---|---|
| 500 mm | 8 mm | 1200 mm | 200 GPa | 0.30 | 250 MPa | 0.85 | 2.0 | 0.42 MPa |
| 750 mm | 10 mm | 2000 mm | 70 GPa | 0.33 | 240 MPa | 0.80 | 2.5 | 0.08 MPa |
| 24 in | 0.375 in | 72 in | 29000 ksi | 0.29 | 36 ksi | 0.90 | 2.0 | 13.74 psi |
It estimates the pressure at which a thin cylindrical shell may buckle or reach a yield-based limit under uniform external pressure. It also reports an allowable pressure after applying a safety factor.
No. It uses a classical screening approach for quick engineering estimates. For production design, verify the shell with the governing standard, fabrication tolerances, stiffeners, and detailed load cases.
Elastic buckling pressure scales with the cube of thickness-to-diameter ratio. A small thickness increase can raise buckling resistance a lot, especially for very thin shells.
External-pressure resistance depends on effective wall thickness. Corrosion allowance reduces the remaining section, which lowers both the elastic buckling estimate and the yield-limited pressure.
It reduces the ideal elastic buckling prediction to reflect real shells that may have ovality, dents, weld mismatch, or other geometric imperfections. Lower values mean a more conservative estimate.
The calculator compares elastic buckling and yield-limited pressure. The smaller value controls. That tells you whether instability or material yielding limits the shell first in this simplified model.
Yes. Each geometry and pressure input has its own unit selector. The calculator converts everything internally to SI units and then displays the final pressures in your selected output unit.
That means the applied external pressure is above the allowable estimate. Increase thickness, reduce diameter, improve restraint, lower imperfections, add stiffening, or perform a more detailed shell design check.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.