UG-45 Minimum Nozzle Neck 1

[aaloui]

Hello,

can some one explain the technical background behind the thicknesses tb1, tb2 and tb3 (Table UG-45). If the opening is adequately reinforced and the nozzle neck is checked for UG-22 loadings in determining ta thickness so for what are the thicknesses tb1, tb2 and tb3?

Thank you
Ali

 

[SnTMan]

aaloui, I can't prove this, but it is my opinion that the intent of UG-45 is to assure some degree of mechanical strength of the nozzle with respect to attached piping. Note exceptions for manways, etc.

Maybe some else can offer something more definitive

Regards,

Mike

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

 

[TGS4]

When you "check for UG-22 loadings", did you account for the 300lb engineer or pipefitter that will use the small nozzle as a step? Start thinking in that direction and you will get to where the minimum nozzle neck thicknesses might come from. In the end, there may be no calculatable technical justification, but rather the collective wisdom of the engineers that were members of the Code Committee at the time that this rule was last revised.

 

[SnTMan]

Hmmm, I might better have said "...attached piping and other loads.."

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

 

[IdanPV]

I tried to find a reasonable explanation to these thicknesses but it seems that there isn't.
To be honset - You doesn't even need tb1 and tb2 because the math is slightly wrong (or tricky)
For example - assume you need an NPS 3 Nozzle (not an access opening (ta)) for a pressure vessel, even in the worst case scenario that the required vessel wall thickness is infinity it doesn't even matter.

Example:
tb1=infinity.
tb2=infinity.
tb3=4.80mm.

tb=min(tb3,max(tb1,tb2)). therefore - tb=min(tb3,tb2 or tb1)=>tb=tb3.
And hence, you doesn't even need to calculate or take care of tb1 or tb2, just assume you need infinite wall thickness for the vessel

 

[SnTMan]

tb=min(tb3,max(tb1,tb2))

So this eqn permits tb to be equal to (for example) tb1 and thinner than tb3.

If ta is then less than tb, tUG45 is equal to tb1, and is thinner than tb3.

If ta is greater than tb, tUG45 is equal to ta, but need not be compared to tb3.

By my reading anyway.

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