HARSLE
Engineering Calculator
Tube Bending Wall Thinning
Rate Calculator
Quickly compute wall thinning from measured data or estimate it from bending geometry. Supports mm and inch units with built-in safety thresholds per ASME B31.1/B31.3 guidelines.
Reference Diagram — Bent Tube Cross-Section
Measured Thinning
Based on actual thickness measurements before and after bending
W = (T₀ − T_min) / T₀ × 100%
Theoretical Estimation
Estimate from tube geometry and bending radius (pre-bend planning)
W_est = D / (2R + D) × 100%
Nominal OD of the tube before bending
Distance from bend centerline to tube centerline (CLR)
Bend Ratio (R/D): —
Industry Standards & Acceptance Thresholds
≤ 10%
Acceptable
High-pressure hydraulic lines, boiler tubing (ASME B31.1). Standard aerospace & automotive target.
10% – 15%
Marginal / Review Required
General process piping (ASME B31.3). Engineering review recommended. Consider material upgrade.
> 25%
High Risk — Reject
Exceeds most industry limits. Risk of burst, fatigue cracking, and joint failure under pressure cycles.
| Standard | Application | Max. Thinning | Min. Bend Ratio (R/D) |
|---|---|---|---|
| ASME B31.1 | Power piping | ≤ 10% | ≥ 3.0 × D |
| ASME B31.3 | Process piping | ≤ 12.5% | ≥ 1.5 × D |
| EN 13480 | Industrial piping (EU) | ≤ 12.5% | ≥ 2.0 × D |
| AS 4041 | Australian pressure vessels | ≤ 15% | ≥ 1.5 × D |
| Aerospace / Hydraulics | Aircraft / high-cycle fatigue | ≤ 8% | ≥ 4.0 × D |
Note: Values shown are general guidelines. Always refer to the applicable code edition and project-specific engineering specifications. Actual acceptance criteria may vary based on material grade, service temperature, cyclic loading, and weld quality.
Estimated Thinning vs. Bend Ratio (R/D)
Visual reference — tighter bends produce more thinning. Hover/tap bars to see values.
How to Use This Calculator
Method 1 — Measured
- Measure original wall thickness T₀ with a UT gauge or micrometer before bending.
- After bending, locate and measure the thinnest point on the extrados (outer arc). Record as T_min.
- Enter both values and press Calculate.
- Compare the result to your applicable code limit.
Method 2 — Estimation
- Enter the tube outside diameter D (nominal OD).
- Enter the centerline bending radius R from your tooling or design drawing.
- Press Estimate to get a theoretical prediction.
- Use to pre-screen feasibility — actual thinning may vary due to material spring-back and tooling.
