App. 2 Flange from Plate

[hakkik]

We need a body flange(App 2 fig 2.4(3a)) and bolted cover for a Div1 vessel with design pressure 3,5 barg@100°C

Can we make(fabricate) this flange(and cover) from plate material and welded in 3 or more segmets. There is some info on hubbed type flanges at 2-2(d) but nothing about ones without hub.

I usually go with the forged ring but this time pressure is low and thickness of flange is 40mm approx.

Thanks in advance

 

[jamesl]

Yes, you can make this (ring) type of flange from plates.

You cannot machine hubbed flange from one plate.

 

[rneill]

You can roll plate and then machine this to make a flange but you can not machine a flange out of flat plate. However, there is one exception to this, the hub (bolting) portion of a flange can be machined out of plate provided there is a proper nozzle neck and this is essentially a slip on hub over the nozzle neck.

From ASME Section VIII Appendix 2-2
(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:
(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 treatment and radiography
requirements shall be the lesser of
t or
(A ? B)/2
where these symbols are as defined in 2-3.
(c) the back of the flange and the outer surface of
the hub are examined by either the magnetic particle
method as per Appendix 6 or the liquid penetrant method
as per Appendix 8.