Cobra17, Thank you very much for your replies.
I took a look at UG-53. The same ligament eff. is used in App. 13, however in UG-53 it says ligament eff. for holes drilled on cylindrical shell. Is this ligament eff. the same for both cases?(drilled shell and drilled plate)
In UG-53 theres this "p 1 = unit length of ligament" what does it mean by unit length? And one more question, I also have a nozzle on short side of my header box. How do I consider that? By using ligament efficiency again in the formula?