Is this an ASME B31.3 pipe-thickness calculation?

No. It is general thin-wall membrane arithmetic. The complete current code, material data and project design basis are required for pressure design.

Does the result select a pipe schedule?

No. Product dimensions, tolerances, material condition and availability must come from the controlled product specification.

Is the calculated pressure wall a burst thickness?

No. The entered stress is a documented screening limit, not ultimate strength, and failure modes and code requirements are not modeled.

Why is internal diameter required?

The displayed force-equilibrium equation uses the internal radius at the assessed pressure-boundary state. Nominal DN or NPS is not an internal diameter.

General membrane mechanics — not code pressure design

Thin-Wall Internal-Pressure Screening Arithmetic

Calculate an ideal hoop-membrane pressure wall from a controlled inside diameter and documented effective stress limit, then apply a documented unavailable-wall allowance and negative manufacturing tolerance. No schedule, MAWP, burst pressure or code-compliance result is generated.

Inside-diameter basisGauge-pressure differenceThin wall onlyNo ASME verdict

Arithmetic minimum nominal wall

Pressure-resisting wall tp

Minimum delivered wall tn(1−m)

Thin-wall ratio tp/ri

Ideal closed-end axial membrane stress

General arithmetic only.

σh=P·ri/tp=P·Di/(2tp) → tp=P·Di/(2σlim)
tn,min=(tp+c)/(1−m)

P is differential gauge pressure; Di and ri=Di/2 are the controlled internal diameter/radius at the assessed state; tp is effective wall resisting pressure; σlim is a documented permissible effective hoop-membrane stress; c is total unavailable wall; m is a decimal maximum negative manufacturing tolerance; tn,min is the arithmetic nominal wall before that tolerance. Pressure and stress must use the same units; all lengths must use the same units.

For an ideal closed-end thin cylinder, the axial pressure membrane stress at tp is σa=P·ri/(2tp)=σlim/2. The result does not include any other axial, bending, torsional, thermal, local or cyclic load.

Applicability gate

The calculator suppresses results when tp/ri>0.1. The public University of Illinois derivation treats the thin-wall approximation as sufficient at ri/t≥10 and explicitly states uniform through-wall stress and neglected radial stress. Passing this numerical screen does not establish code applicability.

Not a design or acceptance result. No external pressure/buckling, transient/surge, fatigue, creep, thermal gradient, weight, supports, vibration, seismic/wind, ovality, defects, threading/grooving, bends/branches, weld reinforcement, stress concentration, fracture, test pressure, fabrication, inspection or uncertainty is evaluated.

Standards boundary

ASME B31.3-2024 is the current process-piping code record and covers materials, components, design, fabrication, assembly, erection, examination, inspection and testing. Its exact pressure-design equations, coefficient tables, allowable stresses and service rules are licensed content and are not reproduced here.

ISO 4200:1991 edition 4 is published and under review. It is a general table of dimensions and masses for plain-end welded/seamless steel tubes, not a pressure-design approval. Product dimensions and tolerances must come from the selected controlled product specification.

ASTM A106/A106M-26 is the current ASTM listing for seamless carbon-steel pipe for high-temperature service. The old universal 138 MPa, 12.5% and schedule claims have been removed; exact material/tolerance/product rows require the complete applicable standards.

NEEDS_LICENSED_SOURCE: selected-code equation and limits; S/E/W/Y or equivalent factors; allowable-stress tables; material/product tolerances; corrosion/erosion/mechanical allowances; schedule dimensions; MAWP, test and acceptance procedures.

Kilder

University of Illinois thin-walled pressure vessels; Purdue ME323 summary; ASME B31.3-2024 official record; ISO 4200:1991; ASTM current steel-standards listing; NIST conversion factors.