Pipeline wall thickness is calculated as per API RP-1111, ASME B31.8 (multiphase pipeline) and ASME B31.4 (Water injection pipeline) using the following expression:
t_{nom} = {[(P_{i} - P_{o})D] / [2(F_{1} - L_{f} - T - s_{y})]} + t_{corr}
Where:
P_{i} = Internal Pressure
P_{o}= External hydrostatic pressure
L_{f} = Longitudinal joint weld factor (1.00)
T = 1.0, temperature derating factor (Equals 1.0 for T<250°F)
s_{y}= Specified Minimum Yield Stress
t_{corr} = Internal corrosion allowance
D = Pipe outside diameter
F_{1} = Design Factor
t_{nom} = Nominal pipe thickness