Threaded coupling in flat cover (manway) UG-45 6

[Mr.blu]

I have seen many posts on the forum about this topic, but I haven't found one that really answers this question.
I will try to be as clear as possible: I have a flat cover that I designed according to UG-34 for a filter, which serves as a manway to change filter elements. If I place a threaded coupling on this cover to function as the equipment vent (it will not have external loads), should it comply with the requirements in UG-45, or would it fall under the 'manway opening'? The idea is to install a 1/2" NPT Class 3000 coupling, but its thickness, while meeting the required thickness + CA and UG-16, does not reach the value in the UG-45 table + CA. It is mainly to understand if a connection placed in a manway is still exempt from what is required in UG-45 when there are no external loads.

What does the code consider within 'manway and access only nozzles' if what I'm saying is incorrect? Is there any part of the code that specifies that UG-45 is aimed at reinforcing connections due to external stresses from piping? Many people express that opinion, but I haven't found it explicitly stated.

Thank you in advance to anyone who can help me interpret this

 

[DriveMeNuts]

10mm of the unthreaded end of the half inch coupling is of 4.09mm thickness.
The weld connecting the coupling to the vessel is approx 6mm away from the start of the thread.
As Fig. UW-16.1 Note 1 refers to threaded couplings as nozzles, this 10mm length could constitute the nozzle neck, and the threaded portion could constitute the piping connection (e.g. threaded, flange etc.).
The threaded couplings in Fig. UW-16.1 are shown as full thread, which only adds confusion.
UG-45 refers to thickness required for internal pressure (plus corrosion and threading allowance). So, does that mean that you subtract thread thickness from the unthreaded length? That doesn't make sense. Why would you subtract a phantom thread thickness? It is my judgement that you don't subtract the phantom thread allowance from the unthreaded section.
It seems reasonable that the unthreaded nozzle neck comply with UG-45, while interpretation VIII-1-83-217 applies to the threaded portion.
That is just my thoughts.
If you set the coupling into the vessel and the weld encroached over the start of the thread (like sketch z-1 of UW-16.1), then the table UG-45 thickness would be after subtracting the corrosion and thread allowance.
I think that engineering judgement is required on a case by case basis. The rules are not decisive.

 

[IdanPV]

Thank you so much.
DriveMeNuts, is there anyway to contact you directly?

 

[GD2]

IdanPV and others,
Table UG-45 have gone through numerous revisions due to its complexity of understanding. It has been finally simplified. The thickness on this table is simply the thickness of a "Standard Wall" of a ASME B36.10 pipe with 12.5% under-tolerance taken out.

Table UW-16.1 is based on the ASME B16.11 fitting OD and the equivalent pipe OD for a threaded fitting. SW fittings exceeds the Table UW-16.1 thickness requirement.

My question is - Table UW-16.1 should have come in UG Section as this is a design requirement. Or does it mean the thickness requirement is at the place of welding i.e thickness at the unthreaded portion?

GDD
Canada

 

[david339933]

Table UW-16.1 is only applicable if fillet welded on the outside only. Therefore should be in UW. I have never used Table UW-16.1.

 

[IdanPV]

GD2, I think that Table UW-16.1 refers to thickness requirement at the place of welding i.e thickness at the unthreaded portion.

This is my interpretation to the conflict between Table UW-16.1 and Table UG-45.
UW-16(f)(3) deals with “fittings not exceeding DN80, that attached by a fillet weld form outside only”.
This statement implies that if we were to employ other weld details as shown in Figure UW-16.1, the requirements of Table UW-16.1 were not govern nozzles thickness, thus eliminating concerns. Additionally, in such cases, the required thickness for nozzles were adhere to the requirements of Table UG-45.

The conclusion is that Table UW-16.1 addresses the required thickness specifically at the weld portion. Consequently, for other areas of the nozzles, such as the thread portion, the minimum thickness shall align with the minimum required thickness delineated in Table UG-45.
This explains why PART UW focuses on the thicknesses of pressure parts, a role traditionally associated with PART UG.

As DriveMeNuts already wrote, when calculating the thickness of nozzle having NPT thread, we should take into account that the threaded portion is not through the entire nozzle length. Therefore, the nozzle thickness (at the weld zone) shall se calculated as follow:
(Nozzle O.D - Tap drill size)/2.
The nozzle O.D refers to the actual nozzle outer diameter.
Tap drill size per B1.20.1 Table 2.