Seismic Minimum Thickness per API 650 Section

[FranklinCY]

Dear All,
Please help me with the following query:

Is the following equation valid? It is being compared:

ts = ((S_T+ * (t - CA)) / Membrane_Stress) + CA

Where:
Membrane_Stress = Maximum Allowable Hoop Tension Membrane Stress per API 650 Section E.6.2.4 (MPa)
S_T+ = Total Combined Hoop Stress per API 650 Section E.6.1.4 (MPa)
t = Installed Thickness (mm)
CA = Corrosion allowance per API-650 5.3.2 (mm))

I found this analysis in a calculation memory, where the thickness in the cylinder is being calculated by means of the previously shown equation

I will appreciate your comments.

Regards.