These formulas are considered reference material only, they are not intended for design purposes.

Calculated Weight Per Foot

W= C (D - t) t

Where W = Weight lb/ft (Kg/m)

C = 10.69 (0.0247) for Carbon Steel, 10.93 (0.0248) for Austenitic Stainless Steel

D= Outside Diameter, in (mm)

t = Wall Thickness, in (mm)

Cross-sectional Area

A = 3.1416 t (D t)

Where A = Sectional Area, in²

D = Outside Diameter, inches

t = wall Thickness, inches

Barlows Formula
For Theoretical Burst Pressure:

P = 2St/D

For Theoretical Working Pressure:

Divide theoretical Burst by 4

For Theoretical Yield Pressure:

Replace S with Y

For Determining Allowable Tube Wall Stress for Hydrostatic Test

s = PD/2t

Where P = Pressure in psi,

S = Minimum Product Tensile Strength

t = Wall Thickness, in

D = Outside Diameter, in

Y = Minimum Product Yield Strength

s = Tube Wall Stress Produced by Internal Hydrostatic Pressure

Determined theoretical burst and working pressure should be de-rated for welded tube and elevated temperatures. Consult the ASME Pressure Vessel Code for specific information.

Moment of Inertia

I = 0.04909 (D⁴ d⁴)

I = Moment of Inertia

D = Outside Diameter, inches

d = Inside Diameter, inches

Carbon Equivalent For
Weldability Rating

CE = C + (Mn/6) + (Cu+Cr/15) + (Cr+Mo+V/5)

C= Carbon

Mn= Manganese

Cu= Copper

Cr= Chromium

Mo= Molybdenum

V= Vanadium