Free Engineering Tool — #154
Pipe Wall Thickness Calculator — Barlow’s Formula
Calculate minimum wall thickness for pipes under internal pressure using Barlow’s formula: t = P×D/(2×S×E). Includes corrosion allowance and tolerance.
Results
Barlow’s Formula
With Corrosion and Tolerance
- P — design pressure
- D — pipe outside diameter
- S — allowable stress at design temperature
- E — weld joint efficiency (1.0 seamless, 0.85 ERW, 0.60 FBW)
- c — corrosion/erosion allowance
- tol — manufacturing tolerance (typically 12.5%)
Given: OD = 114.3 mm, P = 10 MPa, S = 138 MPa, E = 1.0
t = 10 × 114.3 / (2 × 138 × 1.0) = 4.14 mm
+ 1.5 mm corrosion = 5.64 mm
÷ (1 − 0.125) = 6.45 mm minimum
Select Sch 80 (8.56 mm wall) for this service.
⚠️ Note: This is Barlow’s simplified formula. For code compliance, use ASME B31.3 Eq. 3a which includes the Y factor. Always select the next standard pipe schedule above the calculated minimum.
t = P×D/(2×S×E). Calculates minimum wall thickness for pipes under internal pressure. P = pressure, D = OD, S = allowable stress, E = weld efficiency.
Depends on material and temperature. Carbon steel A106 Gr.B at ambient: ~138 MPa. See ASME B31.3 Table A-1 for precise values at design temperature.
E = 1.0 for seamless, 0.85 for ERW, 0.60 for furnace butt welded. Higher E needs more NDE (radiography). Per ASME B31.3 Table A-1B.
Yes. Typically 1.5–3 mm for carbon steel in process service. Also add -12.5% mill tolerance for seamless pipe (per ASTM A106).
ASME B31.3 uses t = PD/(2(SE+PY)), where Y ≈ 0.4 at moderate temperatures. This gives a slightly thinner result. Barlow is conservative.
The procedures described on this page were developed and field-tested by the Vibromera team using the Balanset-1A, a portable dual-channel balancer and vibration analyzer for on-site rotor balancing.
Professional instruments. Used in 50+ countries.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
