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Process reference

Pressure Vessel Wall Thickness Calculator

Turn design pressure and diameter into a first-pass shell thickness for a cylindrical vessel.

Short answerFor a thin-wall cylinder (ASME VIII, circumferential stress): t = P·R ÷ (S·E − 0.6·P), where P is design pressure, R the inside radius, S the allowable stress and E the joint efficiency. Add a corrosion allowance.

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How it's calculated

The hoop (circumferential) stress governs a thin cylindrical shell. ASME’s formula solves for the thickness that keeps that stress within the allowable, adjusted by the weld joint efficiency E. Longitudinal stress needs about half the thickness, so hoop controls. Always add a corrosion allowance and round up to a standard plate.

t = (P × R) ÷ (S × E − 0.6 × P) + corrosion allowance R = inside radius
Worked example
  1. P = 150 psi, R = 24 in, S = 17,500 psi, E = 0.85.
  2. t = 3,600 ÷ 14,785 = 0.244 in (+ corrosion → ~5/16 in).

Reference tables

Typical joint efficiency E

Weld / examinationE
Full radiography1.00
Spot radiography0.85
No radiography0.70

A number the tables do not give: at 150 psi and a 48-inch diameter, a spot-radiographed shell needs about a quarter-inch of steel before corrosion allowance.

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FAQ

Hoop or longitudinal stress?

Hoop (circumferential) governs a thin cylinder and needs about twice the thickness of the longitudinal check, so it controls the shell.

What is joint efficiency?

A factor for weld quality and examination — full radiography earns E = 1.0, less inspection lowers it, increasing required thickness.

Do I add corrosion allowance?

Yes — add it to the calculated thickness, then round up to a standard plate. Service life and fluid set the allowance.

Is this ASME-compliant design?

No — it is the thin-wall shell equation for orientation. A real vessel is designed to ASME VIII in full by a qualified engineer.

This page is a reference aid. Always verify against ASME BPVC Section VIII and a licensed engineer. Figures shown are for orientation, not a stamped design.

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