Chapter IX presents the offshore requirements of B31.4. For more information, see B31.4 and B31.4 Chapter XI.
Calculate Stress Intensification Factors (SIFs), flexibility factors, and section moduli
Calculate all SIFs, flexibility factors, and section moduli exactly as stated in the standard B31.4 code.
Calculate stress using B31.4 Chapter IX
Use the uncorroded wall thickness to make stress calculations.
Calculate load cases using B31.4 Chapter IX
There is no provision for a code check for the expansion load case, so no expansion cases are generated under this code. Operating, sustained, or occasional load cases are treated identically. Do three stress calculations for these load cases, each with a different allowable limit. The Stress Report displays the calculation causing the highest percent of allowable along with its specific allowable. These three stress checks are:
Hoop Stress: Sh £ F1 Sy
Longitudinal Stress: |SL| £ 0.8 Sy
Equivalent Stress: Se £ 0.9 Sy
Where:
Sh = (Pi – Pe) D / 2t, when D/t >= 20
Sh = (Pi – Pe) (D-t) / 2t, when D/t < 20
Pi = Internal Pressure
Pe = External Pressure
D = Outer Diameter
t = Wall Thickness
F1 = Hoop Stress Design Factor 0.60 or 0.72, see Table A402.3.5(a) of the B31.4 Code
Sy = Specified Minimum Yield Strength
SL = Sa + Sb or Sa - Sb, whichever results in greater stress value
Sa = Axial Stress Positive Tensile and Negative Compressive
Sb = Bending Stress
Se = 2[((SL - Sh)/2)2 + St2]1/2
St = Torsional Stress