I am needing help with the use of O'lets on Sec. VIII Div. 1 vessels when the shell thickness is greater than .375". My thoughts are they aren't allowed per UW-16(f)(3)(a)when welded from the outside only. Many people argue its full pen. buts its full pen thru the fitting followed up with a fillet weld in my eyes. My reasoning is that the fitting isn't of uniform thickness thus being connected per Fig. UW-16.2 sketch (m). I am rejecting some venders drawings and calcs. for this and getting a lot of flak. I have spoken to my AIS buddy and he has agreed with me. Compress agrees as well if you check the coupling box instead of the uniform thickness option when designing a new nozzle. I have my venders change to a threaded bosset fitting and I feel this is allowed when welded from the outside only on shells thicker than .375" since the fitting is of uniform diameter and thickness so when designing it in Compress you can check the uniform thickness box and install as a set on. It will default to Fig. UW-16.1 sketch (a) and I am OK with that. Your thoughts?
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