Weld Joint Efficiency for Loading on Nozzle

[DriveMeNuts]

I'm wondering if anyone has heard of progress on whether a joint efficiency needs to be applied to the shell-nozzle junction weld when conducting a WRC 107 assessment?

I ask because an AI is insisting that a joint efficiency be used even though decades of industry experience has demonstrated that is not needed.

From a few WRC 107 assessments I find that the principal membrane stress orientated away from the centre of the nozzle is always less than the other principal membrane stress orientated around the perimeter of the nozzle. (It is 50% at the longitudinal plane and 80% at the circ plane.)

This would suggest that the nature of nozzles geometry automatically includes a joint efficiency of 80%.

This is a very complex topic, especially if you include the assessment of the bending stresses and MPI/PT testing.

My nozzles are full pen and set through.

Previous thread:

https://www.eng-tips.com/viewthread.cfm?qid=366300

 

[TGS4]

What's your Code of Construction?

 

[DriveMeNuts]

It’s designed to ASME VIII Div 1.

Unlike Div 1, Section 4.5.15 of Div 2 specifies that WRC 107 or FEM can be used for nozzle loading and the resulting stresses shall be assessed using the acceptance criteria in Part 5. There is no requirement to add a joint efficiency. If there was a need to consider using a weld joint efficiency, this section would say so. I don't understand why Div 1 would be any different.

As U-2(g) says that “it is intended that the Manufacturer, subject to the acceptance of the Inspector, shall provide details of design and construction which will be as safe as those provided by the rules of this Division.”

Div 1 says that Category D joints don’t have a joint efficiency however one can be applied if needed. In my opinion the requirements in Div 2 (a closely related specification) demonstrates that adding a weld efficiency to nozzle loading is not needed and if applied would make the design “more safe” rather than “as safe”.

I've conducted two separate nozzle analysis with ANSYS with Long and Circ moments and also find that the Principal stress running away from the center of the nozzle (across the weld) at any location is less than the principal stress orientated around the nozzle. (No Internal Pressure was applied.)

This will require many hours of report writing, even though every nozzle by its geometric nature has a built-in acceptable weld efficiency.

When considering the bending stresses, the combined membrane plus bending principal stresses are similar in both directions. Therefore, perhaps this means that the ratchetting assessment does need a weld efficiency. However, MPI and PT examination are used on the surface (where the bending stresses are greatest). Perhaps this testing is good enough to justify using a weld joint efficiency of 1.0....or perhaps not?

Lots of complex questions for an exercise that decades of industry experience seems to have demonstrated is a pointless exercise (and is not required by Div 2).

Is this another case of an AI being over cautious in an area that they are not familiar with?

 

[TGS4]

There is no weld efficiency for that joint. Your inspector is incorrect.

The entire concept behind weld joint efficiency is not applicable to that type of joint.

 

[r6155]

May be the inspector is confused with E and E1 in UG-37.
Good engineering practice for this type of nozzle is round finish the fillet weld, and after this MT or PT.

Regards
r6155

 

[SnTMan]

Seem to be a lot of confused inspectors around these days....

Regards,

Mike

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