ASME V111 Div.1 Weld Category /Type/Joint Description

[regular]

Table UW-12 lists the Weld Type associated with Joint Description and Limitations.
The limitations for Type 3 ( Single welded butt without backing strip)are: Circumferential butt joints only, not over 5/8 " thick and not over 24 in. OD.
Does this mean that the code does not allow a vessel design with circumferential butt joint (of Category A,B or C)that is over 5/8 " thick and over 24 in. OD ?

 

[prex]

Single welded means that you have no access at weld back for gouging and refilling weld root. Under these conditions the limits you state are in effect.
Consider however that with a TIG first pass one can obtain a quality equivalent to that of a double welded joint with access on one side only: this is the preferred solution with respect to backing strip when a high quality construction (fatigue resistance) is sought. prex
motori@xcalcsREMOVE.com

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[ExAI]

I direct your attention to ASME VIII D1 para U-1(a)(3). Unless SPECIFICALLY stated, this code does not establish prohibitions. The limitation you reference is specifically for the assignment of the Efficiency value of the identified weld which does not, in my opinion, form a specific prohibition.
I'm not sure if it applies but para UCS-57 seems to require RT on all carbon steel butt joints greater than 5/8". Performance of RT will "upgrade" your efficiency to the Type 1 catagory anyway. to disguss this further, Email me at
LaneBQS@att.net

 

[regular]

Thanks Prex. Consider the following situation:

I have a Category B circumferential weld in a >24 inch diameter and > 5/8 in.thick that I can weld both sides but choose to do a type 3 joint albeit with a good TIG root run
Does the code allow that ? And also what would the joint efficiencies be for the two non-listed inspection cases ie. full radiography and spot radiography.

 

[regular]

I did not read ExAI's response when I gave the example. But how does full radiography upgrade a joint that is welded from one side (and for which the root weld is definitely not as good as a double side welded one noting that the code accepts certain welding inadequacies or indications.)
Also, the radiography requires full radiography for P-4 carbon steels when the thickness > 5/8 in. For P-1 groups 1 and 2 (more commonly used pressure vessel plates) it is > 1 1/4 in.

 

[prex]

If you make a TIG root pass then your joint will be type 1: of course this is allowed and joint efficiencies are as listed in UW-12.
However I can't see a reason for doing that if you can access the joint both sides: TIG is very lengthy to do and requires back protection (argon filling the entire vessel or using half pipes with rubber joints). It is much simpler to weld a V groove (from inside or from outside the vessel at the choice of the welder, it depends on actual size of vessel, accessibility...), then to grind the root from the other side and close with a small pass.
Concerning ExAI' response, of course radiography could theoretically upgrade the joint type: it is however quite impossible to obtain a type 1 joint conforming to UW-35 (complete penetration and full fusion) without a protective gas on the opposite side of the weld, so that RT standards wouldn't anyway be met... prex
motori@xcalcsREMOVE.com

http://www.xcalcs.com

Online tools for structural design