Pressure Vessel Thickness Calculator

What this calculator does

Performs preliminary internal-pressure thickness calculations for cylindrical shells, spherical shells / hemispherical heads, and 2:1 ellipsoidal heads using common ASME Section VIII Division 1 equation forms.

Screening calculation only: This page does not select allowable stress, establish code applicability, assess external pressure, openings, local loads, fatigue, brittle fracture, forming thinning, minimum thickness, tolerances beyond the entered allowance, or inspection requirements.

Inputs

Component

Design pressure MPa

Inside diameter mm

Allowable stress at design temperature MPa

Weld joint efficiency, E

Corrosion allowance mm

Other thickness allowance mm

Negative mill tolerance %

The equation denominator must be positive. Check pressure, allowable stress and weld efficiency.

The resulting thickness-to-radius ratio is relatively large; verify applicability of the selected equation and consider a more detailed code analysis.

Results

Pressure-design thickness

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Required before mill tolerance

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Minimum nominal thickness

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t / inside radius

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Controlling equation

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Pressure / (S·E)

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Next step: Round up to an available nominal thickness, then perform the complete code design and deduct all applicable allowances in the correct sequence.

What the calculation estimates

The page estimates minimum pressure-retaining membrane thickness for a cylindrical shell, spherical/hemispherical shell or 2:1 ellipsoidal head under internal pressure.

Why it is only preliminary

Pressure membrane stress is only one part of vessel design. Openings, nozzles, external loads, wind, seismic loads, vacuum, local stresses, fatigue, brittle fracture, supports, forming and fabrication tolerances can govern the final design.

How the inputs are used

Design pressure P, inside diameter or radius, allowable stress S and weld-joint efficiency E enter the pressure formula. Use the corroded inside geometry on which pressure acts and the allowable stress at design temperature from the adopted code edition.

Allowances and mill tolerance

Pressure thickness is calculated first. Corrosion and other explicit allowances are added, then nominal ordered thickness is increased for negative mill tolerance. This sequence prevents the manufacturing tolerance from consuming required allowances.

Understanding the equation limits

The formulas have denominator and geometry limits defined by the applicable code rules. The page flags a large t/R ratio as a warning because thin-shell membrane assumptions become less appropriate.

Required engineering checks

A complete code design must verify material specification, temperature limits, joint category, examination, head geometry, forming thinning, reinforcement, load combinations, test pressure and all jurisdictional requirements.