SAE Fittings on ASME Vessel

[JonMills]

I am interested in using SAE straight thread fitting (O-Ring Boss) directly into a hole tapped with matching straight threads on an ASME pressure vessel. ASME BPVC.VIII.1-2015 UG-43e states that threaded connections shall conform to ASME B1.20.1 if they meet the minimum required number of threads. It also says threads should be tapered or straight threads which are at least as strong and can prevent leaks. I am a little confused as to whether this prohibits any fittings not under ASME B1.20.1 even if they use another method to prevent leakage and at least equal strength. Or are fittings which don't conform to B1.20.1 allowed as long as they do not leak and can be shown to be as strong or stronger?

On a semi-related note ASME B31.3 Process Piping Sec. 326.2.1 gives a list of components which are acceptable for pressure design (which includes SAE J513, J514 etc.) but to my knowledge there is no call out like this in the BPVC.

It will be 1/2" fitting through a 1" wall with a large OD so the minimum required engagement of 0.43" is satisfied.

Any insight is greatly appreciated.

 

[XL83NL]

Good question, I've been wondering myself the same thing in the past as well. I'll lurk in to find any good responses.

Huub

 

[SnTMan]

Kind of spit-balling here, but I'd think it should be fairly straight forward to show the SAE straight thread to be equal strength to some B1.20 thread. If so, and if otherwise meeting UG-43(e), I'd say the opening is acceptable. I'd go on to say the fitting itself could be excluded from Code scope.

Detailed knowledge of B1.20 (which I don't have) may prove or disprove that idea.

Another facet: Under older Editions it perhaps would have been possible to introduce the B31.3, Sec. 326.2.1 listed fittings under U-2(g), but I am not sure it is possible under the 2019 Edition, from what I understand from other discussion.

JonMills, I'd say consulting with your AI would be useful if your vessel is to be stamped.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand