ASME Sect. 8 Div.1 thread-o-let and 1/2" pipe wall

[roadapple]

Question:

I am doing a demonstration vessel with 8" sch 80 pipe (1/2" wall), a 8" pipe cap and flange at opposite ends. I intend on putting a thread-o-let on the side of the vessel.

I have all my materials on hand and now I see in my design calc's that UW-16 (3)(a)(1) is limiting me to 3/8" maximum vessel wall.

I can't find where any additional calc's can be done to make this work. Can someone point me in the right direction? Or am I just plain hosed?

roadapple

 

[vesselfab]

you would not use that fig for a thread-o-let

just play it safe and use a coupling and figure uw-16.1(z-1)

 

[jte]

Not sure of the groove dimension on the threadolet, but it seems that you might fall more into the domain of UW-16(f)(4) - Fig UW-16.1 sketch (bb)?

jt

 

[rneill]

I don't believe thread-o-lets are permitted in vessel fabrication since these are not ASME components. They are made to MSS SP-97.

I've only ever seen couplings used for small bore connections as recommended by vesselfab.

 

[roadapple]

I was hoping for an outside fillet weld with the thread-o-let- but am guessing that the moment with the thicker plate is the reason they limit the thickness of the vessel.

I have room to weld a coupling in the arrangement shown in UW-16.1 (i) - because my pipe is 8.625 od the curvature makes saddling the branch a real problem. I am trying to get away from machining an expensive part just to junk it at the end of the review.

 

[roadapple]

Thanks gents - or ladies whatever the case is.

I will be getting a coupling to do this with.

roadapple

 

[vesselfab]

cut a hole in the center of head. there will not be any machining for curvature.

the opening will be flat.

then stick what ever you want to weld in and use a full penetration weld.

 

[PVinspector]

Thread-O-Lets are not banned in Section VIII, but there is no figure in UW-16 that is like a TOL. Also, with the groove built in to the TOL producing a fillet leg is not practical. Use a coupling, and save the TOL for B31.1 work.

The calculations for proving out the weld strength are shown in examples in Section VIII, Appendix L-7, but you will be much happier using the coupling with a standard UW-16 figure.

Your AIA should have advised you on what components to use for the demonstration.