ASME VIII Div. 1 Appendix 2-2(d)(1)

[Mechanimal]

Hi,

I'm hoping someone can explain this to me as I can't figure it out!

ASME VIII Div. 1 Appendix 2-2(d) states:

"(d) Fabricated hubbed flanges shall be in accordance with the following:

(1) Hubbed flanges may be machined from a hot rolled or forged billet or forged bar. The axis of the finished flange shall be parallel to the long axis of the original billet or bar. (This is not intended to imply that the axis of the finished flange and the original billet must be concentric.)

(2) Hubbed flanges [except as permitted in (1) above] shall not be machined from plate or bar stock material unless the material has been formed into a ring, and further provided that..."

Let's say I'm using forged bar. So I'm good to machine a hubbed flange but if I look at UG-6(b):

"(b) Forged rod or bar may only be used within the limitations of UG-14."

Ok so I go to UG-14:

"(a) Rod and bar stock may be used in pressure vessel construction for pressure parts such as flange rings, stiffening rings, frames for reinforced openings, stays and stay‐bolts, and similar parts. Rod and bar materials shall conform to the requirements for bars or bolting in the applicable part of Subsection C.
(b) Except for flanges of all types, hollow cylindrically shaped parts [up to and including NPS 4 (DN 100)] may be machined from rod or bar, provided that the axial length of the part is approximately parallel to the metal flow lines of the stock. Other parts, such as heads or caps [up to and including NPS 4 (DN 100)], not including flanges, may be machined from rod or bar. Elbows, return bends, tees, and header tees shall not be machined directly from rod or bar."

UG-14(b) restricts the use of rod or bar for all flange types.

It would appear that I can only use bar for flange rings per UG-14 and appendix 2-2(d)(2).

Appendix 2-2(d)(1) appears to contradict UG-6 / UG-14. What am I missing? Should Appendix 2-2(a) add the phrase "with the following additions and exceptions"?

 

[GenB]

there is no contradiction,
"(1) Hubbed flanges may be machined from a hot rolled or forged billet or forged bar" one condition: parallel

the MAY BE machined. may be machined w/o any other conditions. The others have different conditions.

 

[Mechanimal]

But UG-14(b) restricts the use of rod or bar for all flange types and via UG-6(b) forged bar would appear to have the same limitations.

Also Appendix 2-2(a):

"(a) Materials used in the construction of bolted flange connections shall comply with the requirements given in UG-4 through UG-14."

So how do I comply with UG-6 & UG-14 when Appendix 2-2(d)(1) is contradicting their position?

 

[SPDL310]

UG 14 specifically excludes certain parts from being machined out of bars and forgings, flanges are not on the list of excluded components. It does tell you to comply with the rules for bars or bolting from subsection c which would be UCS 10 or UCS 12. As long as those regulations are followed in tandem with the requirements of annex 2-2 you should be good.

To clarify the above some UG 14 blanket authorizes certain components to be machined from forged bars. It also forbids others like elbows from being machined at all. Appendix 2-2 authorizes flanges to be machined from forged bars provided that in accordance to UG 14 the requirements of UCS 10 or UCS 12 are met.

 

[Mechanimal]

I would interpret UG-14 to mean flanges even 4" NPS and below cannot be machined from hot rolled bar or forged bar. Which is a common statement in SA-182, SA-105, and SA-961. So it would appear the ASME is trying to follow the current material specifications.

But Appendix 2 appears to contradict this.

Even this article points to the paradox that exists:

Link

My understanding of forging the rough shape of flanges relates to grain flow lines. See attached document.