Tube Collapse Pressure Calculator
Plotly Graph
The graph sweeps wall thickness from 50% to 150% of effective thickness while keeping other values fixed.
Formula Used
Effective thickness: te = t - c
Mean diameter: Dm = Do - te
Elastic collapse pressure: Pe = [2E / (1 - ν²)] × (te / Dm)³
Yield collapse pressure: Py = 2σy × (te / Dm)
Adjusted governing pressure: Pg = min(Pe, Py) × (1 - ovality / 100)
Allowable collapse pressure: Pallow = Pg / SF
Where t is wall thickness, c is corrosion allowance, E is Young’s modulus, ν is Poisson ratio, σy is yield strength, and SF is the safety factor.
This calculator uses quick screening equations for thin cylindrical tubes under external pressure. Real projects may require code-based collapse checks, ovality measurements, fabrication tolerances, temperature effects, and collapse interaction methods.
How to Use This Calculator
- Enter the outer diameter and wall thickness of the tube.
- Add corrosion allowance to reduce the effective load-carrying wall.
- Enter Young’s modulus, Poisson ratio, and yield strength for the material.
- Input ovality percentage if the tube is not perfectly round.
- Choose a safety factor for allowable pressure estimation.
- Optionally enter a design external pressure to check utilization and margin.
- Select your preferred units, then click the calculation button.
- Review the result table, governing failure mode, export files, and the thickness sensitivity chart.
Example Data Table
| Case | Outer Diameter | Wall Thickness | Material E | Yield Strength | Ovality | Safety Factor | Allowable Collapse | Governing Mode |
|---|---|---|---|---|---|---|---|---|
| Steel Tube A | 100 mm | 5 mm | 200 GPa | 250 MPa | 1% | 1.50 | 17.37 MPa | Yield collapse |
| Steel Tube B | 150 mm | 4 mm | 200 GPa | 250 MPa | 2% | 1.50 | 5.92 MPa | Elastic collapse |
| Steel Tube C | 50 mm | 3 mm | 200 GPa | 250 MPa | 1% | 1.50 | 21.06 MPa | Yield collapse |
Example values are illustrative screening examples, not fabrication or code approval values.
FAQs
1. What is tube collapse pressure?
Tube collapse pressure is the external pressure level that causes instability, yielding, or sudden inward deformation of a tube or cylindrical shell.
2. Why does this calculator compare elastic and yield collapse?
Thin tubes may fail by buckling before material yielding, while thicker tubes may reach yield first. Comparing both helps identify the governing limit.
3. Why is corrosion allowance included?
Corrosion reduces effective wall thickness. Even a small thickness loss can lower collapse resistance because the thickness ratio strongly affects the result.
4. What does ovality change in the result?
Ovality represents out of roundness. A less round tube usually collapses earlier, so the calculator applies a simple derating factor for preliminary estimates.
5. Is the result suitable for final design approval?
No. This page is best for screening and quick comparisons. Final approval should use the applicable code, test data, tolerances, and project rules.
6. What is a good safety factor?
That depends on code requirements, loading uncertainty, consequence of failure, and inspection quality. Many projects use higher factors when uncertainty is larger.
7. Can I use inches and psi?
Yes. The calculator supports mm or inches for size, psi or MPa for strength inputs, and several output pressure units.
8. Why does allowable pressure change so much with thickness?
Elastic collapse varies with the cube of thickness ratio. That makes external pressure resistance highly sensitive to even modest wall changes.