Theoretical membrane thickness
mm
Thin-membrane thickness before allowance and tolerance.
Fluid mechanics · Piping and pressure
Pressure pipe wall pre-sizing
Invert the same mean-diameter model used by the stress calculator, add an allowance, then check wall thinness.
Created v1.0
By Thibaut Grzelak, Mechanical Analysis Engineer
03
MetricResults
Thickness with allowance c
mm
Sum tp + c, without rounding to a commercial series.
Resulting inside diameter
mm
Di = Do − 2tn.
Dm/tp ratio
—
Geometric consistency check using theoretical thickness.
View calculation detailsFormulas, SI conversion, numerical substitution and resultsOpen ↓
Calculation note
Full calculation details
Adopted range: ri/t > 10, with ri = Do/2 − t (inner radius). This limit is a conservative choice for the membrane model, not a code-compliance check. For a calculated thickness, both the theoretical thickness and the thickness including allowance are checked. Thin-membrane pre-sizing for a straight pipe under internal pressure only. The relation inverts σθ = p(Do−t)/(2t), using S·E as a simplified limit. Allowable stress and joint efficiency are already selected by the user. No negative tolerance, temperature effect, external load or code combination is added automatically. Final sizing must be checked using the applicable code and an actually available thickness.
01Formulas and symbols
Formulas used
tp
tp = p·Do/(2·S·E + p)Exact inversion of the mean-diameter modeltn
tn = tp + cThickness after adding allowanceDi
Di = Do − 2tnGeometric inside diameter02Assumptions and limits
Scope of validity
- Thin-membrane pre-sizing for a straight pipe under internal pressure only.
- The relation inverts σθ = p(Do−t)/(2t), using S·E as a simplified limit.
- Allowable stress and joint efficiency are already selected by the user.
- No negative tolerance, temperature effect, external load or code combination is added automatically.
- Final sizing must be checked using the applicable code and an actually available thickness.
03Validation example
Reference numerical case
- p = 40 bar, Do = 114.3 mm, S = 120 MPa, E = 100% and c = 1.5 mm.
- tp = 1.87377 mm.
- tn = 3.37377 mm.
- Di = 107.55246 mm and Dm/tp = 60.