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nachocivicos (Chemical)
28 Sep 08 16:30
Hi,

Regarding flange calculations according to ASME Section VIII Div. 1 Mandatory Appendix 2, the paragraph 2-7 seems quite obscure to me; loose or integral-type formulas appear to be "interchangeable" to some degree provided a hub "is considered" or not (?). I would appreciate very much some orientation in these two specific cases in Fig. 2-4:

- Could sketch (4a) flange be calculated as integral in some case?
- Which is the meaning and value to be taken for the parameter h ("hub length") in sketch (7), where a hub is not present? is it related to weld dimensions?

Thank you very much in advance,

J.I.G.C.
Chemical Eng.
Helpful Member!(2)  gr2vessels (Mechanical)
28 Sep 08 21:38
The integral flanges are defined by that solid extension at the back of the flange called tapered hub. Other "flanges" and hub assemblies are considered integral if sufficient full penetration weld is uniting the flange and hub. The only weld may be considered to give integral quality is the full penetration weld, refer Figures 2-4. The loose flanges show fillet weld of the "hub" to the pipe / nozzle neck. That is not considered strong enough for integral flange qualification. Refer also to the Clause 2-4(a)(1) definition of the loose flange.
When in doubt of the strength of the weld joining the flange end hub, design it as loose flange, but if you opt to design it as integral flange and it breaks in operation, it's your neck ...
Sketch 4(a);- if the weld on the back of the flange in sketch 4(a) looks like the weld on the back of the flange in sketch 8, then it can be designed as integral flange. Otherwise, the fillet weld in the back of the flange of sketch 4(a) will qualify only for the name of loose flange.
The sketch 7 shows a welded flange assembly resembling the sketch 5, which in turn resembles the forged "long weld neck flanges" and the like. It is also explained in the Clause 2-8(a)(1)(a)  "...integral type [Fig. 2-4 sketch (7)] where the neck material constitutes the hub of the flange;"
Phew, it takes some sweat to select the correct words to explain the old cook book and I'm still not sure of it. I suggest you, to sit down and read carefuly every page, clause, note and flange detail on the sketches, then chew on it a few days, it will dawn on you one day and you'll be happy.
Cheers,
gr2vessels
nachocivicos (Chemical)
29 Sep 08 16:39
gr2vessels,

Thank you for your analysis; It helped me see it a bit more clear. But my last question still remains: for example for sketch 7, which value should I take for parameter h in calculations? It does not seem to correspond to any weld dimensions...

Thank you very much again,

J.I.G.C.
Chemical Eng.
Helpful Member!  SnTMan (Mechanical)
29 Sep 08 17:21
nachocivicos, taking your last question first, Sketch 7, the hub length is shown in the sketch as the leg of the fillet weld, hub dimensions g0 and g1 are also shown.

Sketch 4a) would not be considered an integral flange, due to the attachement welds, however the hub may be considered in the flange design, see also 2-7.

Study the various sketches carefully as well.

Regards,

Mike

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