ASME B16.11, wall thickness for threaded fitting for Section VIII-1

[CGarfield]

I've been asked to design a compressed air receiver. The tradesmen that will fabricate it want to use threaded half couplings for the nozzles. When I did my calculations, I used the "G" dimension from ASME 16.11, deducted the corrosion allowance, and then deducted the thread allowance to get the corroded wall thickness. I then compared this thickness to the thickness I calculated using UG-27 for minimum wall thickness. My QA inspector that is reviewing my calculations doesn't agree with this. He suggested that I consider the statement in 16.11 that states the fittings are matched to the various wall thicknesses of pipe. He said I should use the pipe wall thickness, deduct the corrosion allowance and the thread allowance, and compare this corroded wall thickness to the thickness calculated using UG-27. I can see his point, but I don't agree with his way of determining the corroded wall thickness. Can anyone tell me the correct way to determine the corroded thickness of a threaded fitting (ASME B16.11)? Thanks in advance for any advice you can give.
Brian

 

[CGarfield]

One other thing I was going to add but hit "submit post" too quick. The way of calculating corroded wall thickness as suggested by my QA inspector is basically the same as what you would do if you were using a piping code such as b31.3. I'm just not sure if this is acceptable for ASME section VIII-1. Thanks.