Pipe Wall Thickness (Barlow’s Formula)
Pipe Wall Thickness (Barlow’s Formula)
Pressure piping is sized so the hoop stress stays within the allowable. Barlow’s formula gives the minimum wall directly.
Rearranging the hoop-stress relation, t = pD/(2S). where p is the internal pressure, D the outside diameter and S the allowable stress.
Inputs
p := 5 MPa=5 MPa
D := 300 mm=300 mm
S := 120 MPa=120 MPa
Solve the hoop-stress equation for thickness.
t := p·D/(2·S)=6.25 mm
Results
Add a corrosion allowance and mill tolerance to this minimum, then round up to a standard wall. Barlow is slightly conservative as it uses the outside diameter.
Assumptions & limitations
- Thin-wall hoop-stress basis.
- Static internal pressure only.
- No corrosion/threading allowance included here.