UG 45 nozzle neck check
UG 45 nozzle neck check
(OP)
when UG 45 checks nozzle neck T , one of the factors used is a comparison to a chart which list nominal pipe OD and thickness
this was put in 20010 ed. we ran into this on a project , using tube instead of pipe for a small 5/8" drain tube on a small vessel. everything else passed i.e. pressure , weld size etc except for the comparison to the nominal pipe chart is anyone familiar with the intent of including a comparison to the chart just curious when all else passes this item kicks it out.
this was put in 20010 ed. we ran into this on a project , using tube instead of pipe for a small 5/8" drain tube on a small vessel. everything else passed i.e. pressure , weld size etc except for the comparison to the nominal pipe chart is anyone familiar with the intent of including a comparison to the chart just curious when all else passes this item kicks it out.





RE: UG 45 nozzle neck check
Prior to introduction of the table, UG-45 thickness was goverrned by some verbiage such as "Std wt + corrosion". I have found in some instances work that complied previously will not now.
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: UG 45 nozzle neck check
Yes, the intent of these minimum thicknesses is to create a bit of robustness. I would argue that this determination should be left to the engineer, but it's not such a big deal for new construction. And keep in mind, the Section VIII folks are strictly interested in new construction. In a post-construction environment, in many cases trying to adhere to strict compliance with an arguably arbitrary requirement such as UG-45 minimum thicknesses is not aligned with what I consider to be good engineering. In most cases the loads from attached piping are easily determined and their impact on the nozzle can be checked. For example, if Sch. 10 piping is flanged up to the nozzle, why does it suddenly need to be Sch. 40 on the vessel side of the flange? Where's the continuity of logic there? In such circumstances, I usually recommend a quick FFS and weld buildup at the next scheduled shutdown as it is easier to perform the weld buildup than it is to justify continued operation with nozzle thicknesses less than in the table.
But keep in mind, for relatively low pressures with thin wall shells, tb may be limited by tb1 or tb2, not tb3 (Table UG-45). Thus, it is entirely possible - and in my experience common - for people to think that they are out of compliance since a nozzle wall is thinner than shown in Table UG-45, although it is actually perfectly compliant with tUG-45.
RE: UG 45 nozzle neck check
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: UG 45 nozzle neck check
To put it another way, if the UG-45 method "cooks" in the corrosion allowance and manufacturing tolerance, I shouldn't take it back off of the selected pipe size when comparing suitability. Would you folks agree with this assessment?
Thanks!
BrotherBax
RE: UG 45 nozzle neck check
I think I agree with your approach. Certainly, the mill tolerance is built into the Table, so don't double-account for it.
The issue that gives me pause is that you mentioned designing a shell using pipe first, then move on to the nozzle. Just to be clear, my understanding of UG-45 is that it applies strictly to nozzles. If you are designing a shell using a pipe, then UG-45 is irrelevant to that particular process. But, as you point out, the mill tolerance of the pipe must be considered in establishing the thickness of the shell.
RE: UG 45 nozzle neck check
Thanks!