Calculator methodology
Pressure vessel thickness
This calculator sizes and rates unpierced pressure-boundary components for static internal and external pressure. It reports pressure thickness, nominal thickness after corrosion allowance and mill undertolerance, component utilization, MAWP, new-and-cold MAP, external-pressure capacity, and a sourced hydrotest basis.
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Implemented routes
ASME VIII-1 (2025)
UG-16, UG-27, UG-28, UG-32 through UG-34, Mandatory Appendix 1, UG-99, and Section II-D external-pressure tables.
ASME VIII-2 (2025)
Part 4.3 internal pressure, 4.4 external-pressure buckling with Annex 3-D tangent modulus, 4.6 flat heads, and Part 8 hydrotest pressure.
AS 1210 (2010)
Clauses 3.4, 3.7, 3.9 through 3.15, and the Class 1/2/3/1H/2H hydrotest bases in 5.10.
CSA B51 (2014)
Clause 7.1.1 wrapper around the implemented ASME VIII-1 pressure-thickness procedures, with registration and jurisdiction assumptions.
EN 13445-3
Clauses 5.6, 6, 7.4 through 7.6, 8, and 10. Hydrotest pressure uses the PED Annex I 7.4 minimum basis; EN 13445-5 still governs test execution.
Component coverage
Cylinders, spheres, hemispherical heads, ellipsoidal heads, torispherical heads, cones without a knuckle, and circular flat heads are represented. Route-specific applicability limits are surfaced as blocking validation when an equation or material-data domain is not satisfied.
Flat-head attachment factors are user selected from the applicable standard detail. The calculator will not infer a factor from a written connection description.
Material treatment
ASME VIII-1 and CSA routes can interpolate a small, traceable Table 1A subset for SA-516 Grade 70, SA-106 Grade B, SA-333 Grade 6, SA-105, and SA-240 Types 304, 304L, 316, and 316L. Values outside each stored temperature range are blocked rather than extrapolated. Other routes use engineer-entered properties; EN nominal design stress is then derived from the selected material class.
Design boundary
- External-pressure stability is implemented for every route and exposed component, using unsupported length and route-specific material properties.
- Entered inside dimensions are calculation geometry in the corroded condition; corrosion allowance is deducted from thickness and is not automatically added to diameter or radius.
- New-and-cold MAP restores corrosion allowance to thickness but holds entered geometry fixed, giving a conservative result for uniform internal corrosion; exact as-built MAP requires a separate as-built-geometry run.
- The entered unsupported length must be bounded by code-qualified lines of support. Ring section sizing, inertia, attachment, and junction adequacy remain separate checks.
- Openings, nozzles, local loads, attachments, and component junction reinforcement require geometry that is not part of a shell/head thickness component.
- Fatigue, creep, brittle fracture, wind, seismic, piping reactions, transport, and lifting are separate whole-vessel assessments.
- AS 1210 minimum thickness uses the selected manufacturing route, diameter band, lethal-service multiplier, and Group F/G floor.
- CSA registration and authority requirements are identified but not approved by the software.
Engineering use
Treat the output as a transparent preliminary calculation, not a completed vessel design. Confirm the licensed standard edition, material product form and thickness range, fabrication category, complete load set, test procedure, and jurisdictional requirements before issuing a design.