What is the difference between EN 13445 and ASME VIII?

EN 13445 is the European standard for unfired pressure vessels. ASME BPVC Section VIII is the American standard. Both use similar engineering principles but differ in safety factors, allowable stress definitions, and design-by-formula approaches.

What is weld joint efficiency?

Weld joint efficiency (E) is a factor (0 to 1.0) that accounts for the reduced strength of welded joints compared to the base material. Full radiographic examination typically allows E=1.0, spot examination E=0.85, no examination E=0.7.

What is corrosion allowance?

Corrosion allowance is additional wall thickness added to account for material loss due to corrosion, erosion, or wear over the vessel's design life. Typical values range from 1mm to 6mm depending on the service conditions.

Free Engineering Tool

Pressure Vessel Design Calculator

Calculate required wall thickness for cylindrical shells and heads per EN 13445 and ASME VIII Div.1. Includes corrosion allowance and weld joint efficiency.

EN 13445-3 ASME VIII Div.1 Shell & Heads

Design Pressure (MPa)

Design Temperature (°C)

Vessel Outside Diameter (mm)

Material

Weld Joint Efficiency (E)

Corrosion Allowance (mm)

Quick presets

Results

Cylindrical Shell

Required Wall Thickness (incl. CA)

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Calculated Thickness (excl. CA)

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Inner Radius

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Hemispherical Head

Required Wall Thickness (incl. CA)

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Calculated Thickness (excl. CA)

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2:1 Ellipsoidal Head

Required Wall Thickness (incl. CA)

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Calculated Thickness (excl. CA)

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Flat Head

Required Wall Thickness (incl. CA)

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Calculated Thickness (excl. CA)

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Cylindrical Shell — Internal Pressure

ASME VIII Div.1 (UG-27):

EN 13445-3 (Clause 7):

P — design pressure (MPa)
R — inner radius (mm)
S (f) — allowable stress at design temperature (MPa)
E (z) — weld joint efficiency

Hemispherical Head

2:1 Ellipsoidal Head

Flat Head

Practical Example

Example — Steam Drum

Given: P = 1.6 MPa, OD = 1200 mm, SA-516 Gr.70 (S = 138 MPa), E = 1.0, CA = 3 mm

R = (1200/2) − t ≈ 600 mm (iterative, but for thin-wall: R ≈ OD/2)

t_cyl = P·R / (S·E − 0.6·P) = 1.6 × 600 / (138 × 1.0 − 0.6 × 1.6) = 7.01 mm

t_required = 7.01 + 3.0 = 10.01 mm → use 12 mm plate minimum

⚠️ Note: This calculator provides minimum required thicknesses per code formulas. Actual vessel design must also consider external pressure, nozzle reinforcement, wind/seismic loads, and must be verified by a qualified pressure vessel engineer.

Pressure Vessel Design Calculator | EN 13445 / ASME VIII | Free Online Tool

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026

Results

Cylindrical Shell — Internal Pressure

Hemispherical Head

2:1 Ellipsoidal Head

Flat Head

Practical Example