Pressure Vessel Thickness & MAWP Calculation

Professional Engineering Sizing per ASME VIII Div 1 & Div 2, EN 13445-3, and PD 5500 — Shell, Heads, Conical, MAWP, Hydrotest, and Multi-Component Summary.

Advertisement

1. Project Data

2. Vessel Data & Geometry

Conical Head / Reducer Parameters
UG-32(g): warn if α > 30° (junction check req'd).
For documentation only. Per UG-32(g), cone body thickness is calculated at the large-end diameter (Di above). Small-end is not used in this calculation.
External Pressure Warning: This vessel is subject to vacuum. The calculations provided here are for internal pressure only. You must separately evaluate external pressure/vacuum per ASME UG-28, which involves geometric stiffening parameters ($L/D_o$) and material charts.

3. Metallurgy & Joint Efficiencies

Governs hoop stress. Typically 1.0, 0.85, or 0.70.
Governs longitudinal stress.
Div 2: typically 1.0. EN/PD: weld quality factor z.

4. Design Code Selection

Select the pressure vessel code(s) to include in the calculation. All selected codes are calculated simultaneously and shown in the results.

ASME VIII Div 1 — UG-27, UG-32
ASME VIII Div 2 — §4.3
European standard — Clause 7
UK standard — Appendix A
EN 13445-3 Clause 7 & PD 5500 Appendix A use the same general thin-wall equation form as ASME Div 1 but with different allowable stress bases. EN uses f = min(Rm/2.4, Rp0.2/1.5); PD 5500 uses f = min(Rm/2.35, Rp0.2/1.5). Weld quality factor z (= E₂ above) is typically 1.0 for full RT. Material f values are derived from the selected ASME material UTS/YS properties embedded in the database.
Thickness Summary
Governing Code
-
ASME VIII Div 1
Required Thickness -
ASME VIII Div 2
Required Thickness -
EN 13445-3
Required Thickness -
PD 5500
Required Thickness -
Vessel Details
Nominal Design Thickness -
Hydrotest Pressure ($P_T$) -
Material Stress ($S$)
Allowable Div 1 -
Allowable Div 2 -
Allowable EN (f) -
Allowable PD (f) -
Corrosion Allowance: The required thickness ($t_{req}$) is calculated based on the corroded internal dimensions. The Nominal Design Thickness equals $t_{req} + CA$.
Advertisement

Multi-Component Summary Table

Use + ADD TO SUMMARY after each component calculation to build a complete vessel component table. Click any row to restore those inputs.

# Component P / t_act (psig/in) T (°F) D (in) CA (in) Material ASME D1 Result ASME D2 Result EN 13445 PD 5500 Nom. (in) Hydro (psig)
No components added yet. Configure inputs above and click + ADD TO SUMMARY.
Highlighted row = governing (thickest required thickness) component.

Engineering Reference & Technical Basis

1. ASME Section VIII Div 1 (UG-27, UG-32)

Corroded inside radius $R_c = R + CA$ or diameter $D_c = D + 2CA$.

Cylindrical Shell:

$$t_{hoop} = \frac{P \cdot R_c}{S \cdot E_{long} - 0.6P} \qquad t_{long} = \frac{P \cdot R_c}{2 S E_{circ} + 0.4P}$$

Heads & Conical:

$$t_{hemi} = \frac{P R_c}{2SE_{long} - 0.2P}$$ $$t_{elli} = \frac{P D_c}{2SE_{long} - 0.2P}$$ $$t_{tori} = \frac{0.885 P D_c}{SE_{long} - 0.1P}$$ $$t_{cone} = \frac{P D_c}{2\cos\alpha(SE_{long} - 0.6P)}$$
2. ASME Section VIII Div 2 (§4.3)

Exact exponential equations; higher allowable stresses than Div 1.

$$t_{shell} = R_c \left(e^{\frac{P}{SE_2}} - 1\right) \qquad t_{hemi} = R_c \left(e^{\frac{0.5P}{SE_2}} - 1\right)$$
Note: Ellipsoidal, Torispherical, and Conical in Div 2 require Part 4.3 design-by-analysis. This tool shows N/A for those combinations.
3. EN 13445-3 Clause 7 & PD 5500 Appendix A

European codes use the same thin-wall form with different stress bases.

$$e_{shell} = \frac{P \cdot D_c}{2fz - P} \qquad e_{hemi} = \frac{P \cdot D_c}{4fz - P}$$ $$e_{elli} \approx \frac{P \cdot D_c}{2fz - 0.5P} \qquad e_{tori} = \frac{0.885 P D_c}{fz - 0.1P}$$ $$e_{cone} = \frac{P D_c}{2\cos\alpha(fz - P)}$$

f = allowable stress; z = weld quality factor (= E₂). EN: f = min(Rm/2.4, Rp0.2/1.5). PD 5500: f = min(Rm/2.35, Rp0.2/1.5).

4. Maximum Allowable Working Pressure (MAWP)

Evaluates existing thickness. Uses corroded thickness $t_c = t_{act} - CA$.

$$P_{shell} = \min\!\left(\frac{SE_{long}t_c}{R_c+0.6t_c},\frac{2SE_{circ}t_c}{R_c-0.4t_c}\right)$$ $$P_{cone} = \frac{2\cos\alpha \cdot SE_{long} \cdot t_c}{D_c + 1.2\cos\alpha \cdot t_c}$$
5. Hydrostatic Test Pressure (ASME UG-99(b))

Based on governing MAWP (max of all applicable codes), with stress ratio correction.

$$P_T = 1.3 \cdot MAWP_{gov} \cdot \frac{S_{ambient}}{S_{design}}$$
References
  • ASME BPVC Section VIII Division 1: Rules for Construction of Pressure Vessels (UG-27, UG-32, UG-99).
  • ASME BPVC Section VIII Division 2: Alternative Rules — §4.3 Shells Under Internal Pressure.
  • ASME BPVC Section II, Part D: Material Properties — Allowable Stress Tables.
  • EN 13445-3:2021: Unfired Pressure Vessels — Part 3: Design. Clause 7 (Shells under internal pressure).
  • PD 5500:2021: Specification for Unfired Fusion Welded Pressure Vessels. Appendix A (Design).
  • ASTM / ASME Material Standards: SA-285, SA-516, SA-387, SA-240, SB-265, SB-575, SB-443, SB-209.