EN 13480 Design Stresses Austenitic Steel

Hi,

How are is the Time Independent Design Stress, f, calculated according to EN 13480-2017 in AutoPIPE for Austenitic Steels (A > 35%)?

Given that there are two equations provided in 5.2.2-1:

(1) f = Rp1.0,t/1.5,

OR

(2) f = min(Rm,t/3 ; Rp1.0,t/1.2)

When both the material properties Rp1.0t and Rmt are available, is a particular one of the equations used by AutoPIPE to calculate the design stresses?

For example, material 1.4301 at room temperature, has properties Rm = 500 MPa (minimum), and Rp1.0 = 230 MPa.

Using equation (1) f = 230/1.5 = 153.33 MPa but using equation (2) f = min(500/3, 230/1.2) = min (166.66; 191.66) = 166.66 MPa.

AutoPIPE appears to use the value of 153.33 MPa in the subsequent calculation of allowable stresses, rather than 166.66 MPa, if so, why is this the case?

Thanks.