UW-12(f) 1

[Konrad]

Hi
How do you treat requirements of UW-12(f)? My access to ASME interpretations just expired, maybe someone could help me:

1. Does it require to make these tests only once in a lifetime or each time a new vessel is welded?
2. Does it require to make a test on fillet or edge welds? What about tube-to-tubesheet?
3. Does it require to make a test on each thickness/material combination when a production joint is between different materials?
4. Does it allow making only side bends testing regardless of material thiskness? What about, say 0.6mm?

Thanks,
Konrad

 

[CodeRef]

UW-12(f) has not been interpreted before. No interpretation exists that I can find.
For question 1, I would guess the intention was to test once for all vessels unless the tests are no longer representative of the production welding on each vessel.

I cannot answer 2,3 or 4




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[SnTMan]

Konrad, I read it this way: UW-12(f) permits assigning a joint efficiency without RT. Weld quality is proved for each vessel (or part of vessel) by a test specimen removed from the shell or prolongation of it, except when no long seam is present a coupon may be used.

I'm kind of guessing at the following answers to your questions, since your configuration, materials, etc. are not known:

1) Each vessel
2) Appears to apply to main seam welds only
3) Yes
4) 0.6mm material would appear to be less than the minimum thickness allowed by UG-16. Perhaps QW-150 and QW-160 can answer this question, I don't have convenient access to them

My feeling is that UW-12(f) is only applicable to butt joints, since Table UW-12 assigns lower efficiencies for other type joints, such as lap, fillet, etc.

Maybe someone else can shed some more light on this.

Regards,

Mike

 

[metengr]

UW-12 (f) provides a method to determine an alternative efficiency factor up to a limit of 0.8, where no radiographic examination was performed(see SNTMan's response above). Paragraph (f) applies only to each new vessel, and for weld joints where the efficency factor is greater than 0.80, like double welded butt joints (max E is 1.00 for full RT, 0.85 for spot RT of the same joint type, 0.90 and a single welded butt joint w/ backing for full RT.

No other weld joints apply.

 

[Konrad]

SnTMan, Why each vessel? 0.6mm because of thickness of heat exchange tubes wall. It doesn't say that only shell is addressed.

Metengr, it applies to weld joints where E is NOT bigger than 0.80.


KOnrad

 

[metengr]

Konrad;
If you read the entire UW-12, the "E" values in Table cannot be increased in value (please see UW-12 (a), (b) and (c)). The "E" values can certainly be decreased in value w/o RT as indicated in UW-12 (f). Please re-read this paragraph again.

 

[Konrad]

Metengr,
You are right, UW-12(f) doesn't affect E-factor. It has no provisions to make it higher or lower. It only gives requirements that pertain to welds which have E=<0.8. For my usual work- it covers all welds, except those, which do not have E. My concern is whether I have to conduct mechanical examination of testing plates that represent all welds in a vessel. The case is that I use a seamless shell- there's no longitudinal weld to test the prolongation of the main long seam. I cannot find anything that would limit this requirement only to longitudinal seam of the shell (or whatever else).

On the other hand- OK, I want to make such SIDE BENDING test on 1.5mm stainless shell. How do I do it? What do I prove with it?
Konrad

 

[CodeRef]

I found this in UW-9 ...........Butt type joints only are permitted with pressure welding processes [see UW-27(b)]
which answers question 2



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[Konrad]

CodeJackal, could you please explain me what a "pressure welding process" is? And what it has to do with my question 2?

Konrad

 

[CodeRef]

Well as UW-12(f) starts out, it explains the processes that apply to your question which is the "pressure welding process". Here is the first sentence of UW-12(f).....
...A value of E not greater than 0.80 may be used in
the formulas of this Division for joints completed by any
of the "pressure welding processes" given in UW-27(a).....

So now that we have defined your welding process as a pressure welding process, read UW-9(a)which restricts this process to butt joints only.

Your question 2 asks if the test specimens required by UW-12(f) to prove the pressure welding process apply to fillet, edge or tube to tubesheet welds. And I say you cannot pressure weld anything other than butt welded joints based on UW-9(a).




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[Konrad]

Well, this makes sense- only it's not usual way of defining things.

Just one thing is still not clear to me:

...A value of E not greater than 0.80 may be used in
the formulas of this Division for joints completed by any
of the "pressure welding processes" given in UW-27(a).....

Wouldn't this imply that not all of these processes listed in UW-27(a) are "pressure welding processes", and UW-12(f) applies only to a subset of them?

Konrad

 

[CodeRef]

Yes that is correct.
Only those processes classified as pressure welding processes. see this link for a description of pressure welding processes:

http://www.roymech.co.uk/Useful_Tables/Manufacturing/Welding.html

In UW-27(a) arc welding processes are defined. In UW-27(b) other processes are defined and if you notice after "explosive" there is a footnote 6; defined as "welding through the application of pressure"
I am sure not all "pressure welding process" are listed here.

As far as your question 3, I would say that any material that cannot be represented by weldability per QW-150 and QW-160 needs to be tested.

As for question 4, I still don't know.


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[CodeRef]

Please note correction in above where I stated UW-27(a) and (b) I meant UW-27(a)(1) and UW-27(a)(2)




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[Konrad]

If a "pressure welding processes" applies to those which utilize pressure/force applied on surfaces to be joined, then GTAW, GMAW os SMAW do not fall under UW-12(f). I don't have SecVIII-1 rigt now, but there's an exception for resistance welding. It does need some pressure (I'd rather say force) application, but it's exempted for some reason. Maybe it's because that force is not the main source of energy necessary to join the materials.

Does this story sound believable? It would solve my problem before I need to worry about making those tests.
Konrad

 

[CodeRef]

Correct. Resistance Pressure Welding required variables are presented in QW-263, Article 2, Section IX and a change in pressure is an essential variable to the process.

Therefore, it is a pressure welding process and is also exempted from UW-12(f) specifically in the first sentence provided it is permitted by the rules in the applicable subsections.
Here is the first sentence of UW-12(f).......

A value of E not greater than 0.80 may be used in
the formulas of this Division for joints completed by any
of the pressure welding processes given in UW-27(a),
except for electric resistance welding, provided the welding
process used is permitted by the rules in the applicable
parts of Subsection C for the material being welded.

........and the remaining paragraph............

Test specimens shall be representative
of the production welding on each vessel. They
may be removed from the shell itself or from a prolongation
of the shell including the longitudinal joint, or, in
the case of vessels not containing a longitudinal joint,
from a test plate of the same material and thickness as the
vessel and welded in accordance with the same procedure.
One reduced-section tension test and two side-bend tests
shall be made in accordance with, and shall meet the
requirements of QW-150 and QW-160, Section IX.




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[Konrad]

Thnk you CodeJackal, this is really helpful.
Konrad

 

[Konrad]

ANSI/AWS 3.0:
Pressure welding- A nonstandard term for solid-state welding, hot pressure welding, forge welding, diffusion welding, pressure gas welding, and cold welding.

This is actually closing my problem.
Konrad

 

[CodeRef]

A good article on examining Resistance Weld Nuggets in tube and pipe from "The Fabricator"

http://www.thefabricator.com/ResistanceWelding/ResistanceWelding_Article.cfm?ID=256

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