governing thickness of forged neck welded to shell per UCS-66

[YuJie_PV]

hi all,

i am reviewing a calculation of the MDMT of the forged neck.
it's about how to determine the governing thickness.
it's a forged nozzle constructed of SA-105 produced to fine grain practice and normalized heat treatment.
it's butt welded to the shell constructed of SA-516 70N, which is illustred as following sketch:

i have some question as follows:
1. notes of figure UCS-66 indicates Curve B applies to "A/SA-105 forged flanges produced to fine grain practice and normalized, normalized and tempered, or quenched and tempered after".
it's specific to forged flange, what if it's a forged neck? not curve B?
2. what is the governing thickness of the forged neck in determining its MDMT? 18mm(thickness of neck-to-shell weld)? or 73.5mm(thickest portion of the neck), or 20mm(thickness of neck-to-flange weld)?

BTW, the interior thickness of 6.5mm is stainless steel cladding.

any comments appreciated.

 

[SJones]

https://www.eng-tips.com/search.cfm?query=impact testing A105

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[YuJie_PV]

@SJones
i indeed read lots of threads of UCS-66, but i find no post explicitly dedicated to my inquiries.

especially regarding the governing thickness, i looked through Figure UCS-66.3, i still can't get the philosophy of the CODE.

for example, is the tg1 in sketch(h) is just the governing thickness of the corner weld or governing thickness of the entire forged neck?
it's puzzling.

any comments appreciated.

 

[GD2]

Op, there is no confusion. Look closely the x-axis of Fig UCS-66. The figure is interpreted as following:
1.If non-welded part thickness exceeds 6" thickness and MDMT is colder than -48C, use impact tested material.
2. If welded part thickness exceeds 4" and MDMT is colder than -48C, use impact tested material.

The figure UCS 66.3 you posted is for welded construction.

Hope it helps.

GDD
Canada

 

[SJones]

@Yu The definition of “governing thickness” is reasonably clear. What exactly are you trying to evaluate? The MDT for the vessel will already be set, so it is assumed that you are trying to evaluate whether the fitting should be Charpy tested for that MDT. That is probably where the evaluation would go against nominal thickness, as in B31.3, rather than governing thickness. ASME VIII doesn’t appear to work that way. Personally, I wouldn’t let A105 go much below zero deg C without it being Charpy tested.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[YuJie_PV]

@SJones, you're correct, it's a vessel built to ASME VIII-1, i'am trying to evaluate if forged neck shall be impacted.
in the meantime, i am trying to thoroughly figure out how the code is performed in calculating the permissible MDMT of a part without impact testing.

i read through UCS-66, and i understand it as follows, please correct me if any error. thanks in advance.

in the case of the forged neck, i shall use 3 governing thickness (that of two welds, and thickest portion of neck ) respectively, specifically it's 18 mm.20mm,73.5mm, and look up the curve B (SA-105, FG+N) for the MDMT in figure UCS-66.

the warmest MDMT governs, is it correct?

 

[david339933]

3" is not the governing thickness. See UCS-66(a)(1)(-4) again.

 

[YuJie_PV]

@david, do you mean i needn't consider the thickest nominal thickness of the forged neck in determining governing thickness?

 

[david339933]

Assuming your flange is Curve B (SA-105), yes. Your 18mm weld is Curve D to Curve B, while the 20mm weld is Curve B to Curve B (assuming SA-105 flange).
So the 20mm curve B would be the worst case scenario.

 

[YuJie_PV]

thanks david.
why does ASME code ignore the nominal thickness of the neck, which is much thicker than the welds in my case?
heavier thickness, worse toughness, isn't that true? it's confusing.
anyone shed some light on the topic? sorry for so many inquiries.

 

[SJones]

Perhaps, the thrust of your question should be leading you to look at UG-84?

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[YuJie_PV]

Steve, thanks for inspiring me so much on topics of corrosion， while regarding my current question, i don't think i can find any answer in UG-84, which just provides rules on how to perform impact testing.
Thanks.
BTW, i'd like to learn something about the basis on which ASME code committee formulates the rules on MDMT, or the rationale behind the code texts, is there any books available?

 

[YuJie_PV]

someone referenced Example 3.3 in PTB-4, i find it very helpful in understanding the procedure to determine the MDMT in detail.

 

[Ronak_Patel]

@YuJie_PV

Since your nozzle neck is forged, shouldn't it be as per curve "C" {all materials listed in Notes 2(a) and 2(c) for Curve B if produced to fine grain practice and normalized, normalized and tempered, or liquid quenched and tempered as permitted in the material specification, and not listed for Curve D below}??

curve "B" {all pipe, fittings, forgings and tubing not listed for Curves C and D below}

 

[jt1234]

We need AI to read the code, feeding your sketch and question, and provide answer including where the code says right away, instead of so many people wasting time here digging out what in the code or your own interpretation on the code. I got tired of this.