Pipeline wall thickness (ASME B31.4/B31.8)
Design wall thickness by Barlow's formula with the factors of ASME B31.4 (liquid pipelines) and B31.8 (gas pipelines), the corrosion allowance, and the allowable pressure of the selected pipe.
t_min = P · D / (2 · SMYS · F · E · T) + cP_max = 2 · SMYS · F · E · T · (t_n − c) / DPick the nominal wall from the size range at or above t_min; the mill under-tolerance, the minimum wall for handling (D/t) and loads other than internal pressure are checked separately. Interpolate T between the tabulated temperatures; for B31.4 T = 1. Projects under Russian-language codes (SNiP 2.05.06-85*, SP 36.13330) use their own formula with reliability factors.
Source: ASME B31.4, para. 403.2.1; ASME B31.8, para. 841.1.1 and Tables 841.1.6-1, 841.1.7-1, 841.1.8-1
Inputs
You can change a field's unit: the value is converted to the formula's units automatically.
Gauge (internal minus external).
From the line pipe specification or the mill certificate.
Corrosion rate × design life; usually 1–3 mm, more for sour and wet service.
Unit converter for this formulaPressure · Length · Fraction and percent
- MPa1
- kPa1,000
- bar10
- atm9.86923
- kgf/cm²10.1972
- mmHg7,500.62
- MPa(g)0.898675
- barg8.98675
- psi145.038
- psia145.038
- psig130.342
- ksi0.145038
psi and psia are absolute pressure; gauge units (barg, MPa(g), psig) are above atmospheric (101.325 kPa = 14.696 psi). Pressure differences in the formulas do not depend on this.
- t_p — Pressure design thickness (no allowance)–
- P_max — Allowable pressure of the t_n pipe–
- σ_h — Hoop stress at P in the t_n − c wall–
More in Pipelines
Weight per metre of steel pipe and of the whole section, the internal (line fill) volume and the mass of the product in the line.
Friction loss by Darcy-Weisbach (friction factor from Colebrook-White, 64/Re in laminar flow) plus the elevation change; the flow velocity and Reynolds number.
Gas flow rate from the inlet and outlet pressures — the general isothermal flow equation with the Colebrook-White friction factor; gas velocity, average pressure, Reynolds number.
Hoop stress and its percentage of SMYS at the test pressure — at the gauge and at the lowest point of the section, where the water column adds to the pressure.
Free expansion of a section with a temperature change, and the longitudinal stress in a pipeline restrained by the soil, including the internal pressure (Poisson effect); the axial force.
Results are engineering estimates from standard formulas; for design decisions check them against the codes, project documents and specialists' calculations. The formulas carried over from the original set are unchanged, and their errors are described in the notes.