Choosing the correct thickness from Table 5.7b of API 650

[DSTankee]

Column 1 of Table 5.7b of API 650 contains a list of thicknesses of Shell and Reinforcing Plates (t and T). Is this intended to mean the sum, minimum, or maximum of the two thicknesses?

For example;
A tank shell is constructed with a thickness of 1/2" and contains a reinforced shell opening for a nozzle. Calculations considering all design and hydrostatic load conditions are completed and a 3/8" thick reinforcing plate is to be used.

Which of the following thicknesses would be used for reference in Column 1 of Table 5.7b of API 650?:
A - 7/8", the sum of t and T
B - 3/8", the miniumum of t and T
or C - 1/2" the maximum of t and T

I lean towards "B", Otherwise you are very likely to be subject to a reinforcing plate-to-shell fillet weld size , "B" (per column 5), that would be greater than the reinforcing plate.

Any thoughts?

 

[JStephen]

The table is assuming shell and reinforcing plate are the same thickness (typical, but not always the case). I would use repad fillets to match repad thickness, use neck-to-shell fillet to match shell thickness requirement.