[kenton]

Hi,

I have found this:

you determine both your a/l and your a/t for a given thickness. This will likely require linear interpolation(s). You then compare your a/t% to your a/l for that thickness. If your a/t% falls below the allowable a/t% for that thickness, the flaw is allowable.

General formula for interpolation:

http://www.ajdesigner.com/phpinterpolation/linear_interpolation_equation.php

Hope it helps.