Fig UG-34 sketch(b-2): Welding a forged flat head to shell, without doing Tension Test Specimen 2

[Josep Maria Perdigo]

Dear colleagues
I have designed a forged flat head according to fig. UG-34 sketch (b-2) / UG-34(d)(3). The length of flange is quite large, so that the flange-shell weld is away from the corner (radius r) and from the hub (tapered zone).

See attached figure, with dimensions.

The question I have is: Should head-shell welding be governed by figure UW-13.3 / UW-13(g)? In my opinion no, since the welding is not in the hub, therefore it is not a "But-Welded-Hub".
By raising this topic, my intention is to be able to justify to the A.I. that the Tension Test Specimen indicated in figure UW-13.3 / UW-13(g) is not required.

Thank you very much

 

[Cobra17]

Found this interpretation that says the hub can be any length.


Standard Designation: BPV Section VIII Div 1
Edition/Addenda:
Para./Fig./Table No:
Subject Description: Section VIII, Division 1 (1998 Edition, 1999 Addenda); Fig. UW-13.3 Sketch (b)
Date Issued: 01/03/2001
Record Number: BC00-688
Interpretation Number : VIII-1-01-18
Question(s) and Reply(ies):

Question: For the configuration shown in Fig. UW-13.3 sketch (b) of Section VIII, Division 1, the extent of projection of the hub beyond the face of the flat head or tubesheet is not specified. Do the requirements provide for minimum and maximum projection of the hub?

Reply: No.

 

[SnTMan]

Josep Maria Perdigo, mind I am reading from 2017 Ed, so unless the rules have changed since:

UG-34(d)(3) clearly states "...forged circular and noncircular heads integral with or butt welded to the vessel..." and invokes the requirements of UW-13. How do you interpret that your forged head is not butt welded to the vessel?

UW-13(g) states "the hub of a tubesheet or flat head shall have minimum dimensions", no reference to exemption based on other dimensions. The hub "shall meet the following requirements:" which apply when the hub is "integrally forged" or "machined from a forging". How do you interpret that the hub is not either of these?

I would interpret that you are bound by UG-13(g) / Fig. UW-13.3, tension test is required. This test is about the hub, not the weld.

I'd think you'd be on shaky ground with your AI. Are you willing to forgo expense of the tension test and purchase a forged head you won't be permitted to use?

One more thing: It'd be good if you'd state your units in the future

Regards,

Mike

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

 

[Josep Maria Perdigo]

Cobra17, SnTMan, thank you very much for your information and insightful comments. I understand that my position is difficult to maintain.
I saw that, at first glance, there is a lot of difference between my design and Fig UW-13.3, hence my query. But as you say, the difference is not relevant.
To finish: there are no changes in 2019 and 2021 Ed regarding this topic. Dimensions of my sketch are in mm.

 

[r6155]

I consider that its design is not forged, it is upsetting and spinning. See UG-34 (d) (5) sketch (d).

Regards

 

[Josep Maria Perdigo]

I already considered this possibility, but I interpreted that "upsetting and spinning the end of the shell" results in a vessel in which the shell and head are a single piece, without welding (such as gas cylinders), and not is my case.

 

[SnTMan]

Hence use of the word, in UG-34(d)(5): integral

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