Flange Design 1

[Angsi]

I am not sure if I am missing anything here but re Appendix 2, 2.2(d) of Div I (see below):
==================================
(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:
(a) in a ring formed from plate, the original
plate surfaces are parallel to the axis of the finished
flange. (This is not intended to imply that the original
plate surface be present in the finished flange.)
(b) the joints in the ring are welded butt joints
that conform to the requirements of this Division.
Thickness to be used to determine postweld heat treat-ment
and radiography requirements shall be the lesser...etc
==========================

I do not understand why the Code says .."shall not be machined from plate or bar stock material unless the material has been formed into a ring, and ..."

How else would you fabricate a flange/ring? Definitely not a rectangle or a square I think. If I take lets say A516 Gr70 material and machined/cut into a continuous ring, will that be acceptable? Re also 2 (b) above.

Can someone please let me know where I am misinterpreting this?

Thanks in advance.

 

[SnTMan]

Angsi,

My interpretation is that you may not take a piece of plate, burn an ID and an OD from it forming a ring and then machine that into a flange. Because of the plate rolling process I assume the properties will be different around the circumferential direction.

Instead you have to take a strip of plate, form that into a ring or sections of a ring and join with one or more buttwelds.

 

[metengr]

The intent of sentence (2) in part 2-2 of Mandatory Appendix 2 of ASME Section VIII, Div 1 is to permit the use of a forged ring to machine a hubbed flange. Rolled plate or bar will exhibit directional (aka anisotropic behavior) mechanical properties because of specific grain orientation from cold working. This is undersirable for flanges because it could result in variable or reduced mechanical properties.

Instead, by forging or rolling ingots, billets or bar above the recrystallization temperature of the metal you develop a grain structure that is multi-directional with no break lines.

 

[metengr]

The second part of your question in your post was correctly interpreted by SnTMan in using a ring fabricated of rolled plate segments with grain flow of each segment maintained parallel with the axis of the flange. The ring segments would be joined using full penetration butt welds.

 

[JStephen]

Note that various non-ASME-Code flanges are cut from plate as you describe- allowed in AWWA C207, etc.

 

[Angsi]

Thanks for the responses. Appreciated.

 

[arto]

They are worried about laminations/lamellar tearing