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ASME UG-27 Shell Thickness Calculator

Cylindrical shell design per ASME Section VIII Division 1

Design Parameters

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ASME Section VIII Div. 1 UG-27

Disclaimer: This tool is provided for preliminary sizing and educational reference only. Results must be independently verified by a qualified engineer against the code edition, addenda and project specifications that apply to your design. It is not a substitute for a stamped design calculation.

How the UG-27 shell thickness calculation works

This calculator determines the minimum required wall thickness of a cylindrical shell under internal pressure using ASME BPVC Section VIII, Division 1, paragraph UG-27(c)(1). This circumferential (hoop) stress formula almost always governs for cylindrical shells.

The allowable stress is taken from ASME Section II Part D, Table 1A, and linearly interpolated at the design temperature. Corrosion allowance is added, the result is rounded up to the next commercial plate thickness, and the design is checked against the UG-16(b) minimum thickness and any selected Saudi Aramco requirements.

Formulas

Circumferential stress, UG-27(c)(1)
t = P·R / (S·E − 0.6·P)
Design thickness
t_design = t + C
tMinimum required thickness, excluding corrosion allowance
PInternal design pressure
RInside radius of the shell
SMaximum allowable stress at design temperature (Section II Part D)
ELongitudinal joint efficiency per UW-12 (e.g. 1.0 for full radiography, 0.85 for spot)
CCorrosion allowance

Worked example (imperial units)

  1. Design pressure P = 150 psi, inside diameter 36 in, so R = 18 in.
  2. Allowable stress S = 20,000 psi (typical of SA-516 Gr. 70 at moderate temperature; confirm against your code edition). Full radiography, E = 1.0. Corrosion allowance C = 0.125 in.
  3. t = (150 × 18) / (20,000 × 1.0 − 0.6 × 150) = 2,700 / 19,910 = 0.136 in.
  4. t + C = 0.136 + 0.125 = 0.261 in, so the next commercial plate is 5/16 in (0.3125 in).
  5. Validity check: P = 150 psi ≤ 0.385·S·E = 7,700 psi, so the thin-wall UG-27 formula applies.

Limitations and design notes

  • UG-27(c)(1) applies only when t ≤ R/2 or P ≤ 0.385·S·E. Beyond these limits use the thick-wall formulas of Mandatory Appendix 1-2.
  • The longitudinal stress formula, UG-27(c)(2): t = P·R / (2·S·E + 0.4·P), rarely governs unless the circumferential joint efficiency is less than half the longitudinal joint efficiency.
  • UG-16(b) sets a minimum shell thickness of 1/16 in (1.5 mm) excluding corrosion allowance, regardless of pressure.
  • Nozzle openings, external pressure, wind, seismic and supports are outside the scope of this calculator.

References

  • ASME BPVC Section VIII, Division 1: UG-16, UG-27, UW-11, UW-12, Appendix 1-2
  • ASME BPVC Section II, Part D: Table 1A
  • Saudi Aramco 32-SAMSS-004 and SAES-D-001 (where selected)