European Standard – EN 13480-3:2012 Issue 1

Formula

The internal pressures are calculated by using the following formula:

D₀/D_i ≤ 1.7:

P = (2 · (e_ord - c₁) · f · z) / (Do - (e_ord - c₁))

D₀/D_i > 1.7:

P = (2 · (e_ord - c₁) · f · z) · (D₀ - (e_ord - c₁)) / ((e_ord - c₁)2 + (D_o - (e_ord - c₁))²)


Symbol / Description
P Internal pressure (MPa) (*10 => bar)
e_ord Ordered wall thickness (mm)
c₁ Manufacturing tolerance, absolute value (mm)
D_o Nominal outside diameter (mm)
D_i Nominal inside diameter (mm) (Di = Do-2 · eord)
z Welding factor, 1.0 for seamless tubes
f Maximal zulässige Belastung (MPa), siehe unten
A_t Min. ductility, transverse (%)

Austenitic steels

At >= 35%
f = Rp1.0t/1.5 (or min. (Rp1.0t/1.2;Rmt/3), id Rmt is available)* (t = here at temp.)

30% <= At < 35%
f = min (Rp1,0 t/1,5 oder Rm/2,4)*

* The programme always calculates with Rp 1.0t/1.5 for austenitic grades, but if Rmt or Rm are known for the specific grade and size, and at temperatures for Rmt, this may give a more favourable result in case of At > 35% or > 30% as above.

Austenitic steels with At < 30% and steels other than austenitic (here used for the austenitic-ferritic steels, i. e. duplex stainless steels).

f = min. ((ReHt/1,5 oder Rpo.2t/1,5;Rm/2,4)

Attention: Allowed maximum wall thickness
Austenitic corrosion resisting steels 60 mm
Austenitic - ferritic steels 30 mm

Attention: The pressures on these pages are given only as guidance. Dimensioning of piping systems also depends on other factors like external forces, thermal stresses, dead weight etc. Furthermore the design must be made according to regulations from local authorities and approved accordingly.