Flanges Made from Plate Material
Flanges Made from Plate Material
(OP)
I am designing a manway in an ellipsoidal head. Material is ASTM A516 Gr 70.
The manway consists of a door that self seals under the pressure forcing it against the ring that is welded into the head.
My question is: Can this welded ring which is a reversed flange be machined from flat plate? Or must it be forged?
ASME VIII Appendix 2 says Hubbed flanges can't be machined from plate but I can't find any reference to welded slip on or slip in flanges.
The material is strong enough with and across the grain to pass the design. However my 3rd party design appraisers give a reason of fatigue in that if there are imperfections between the elongated grain structure then these may grow and the flange will split (like a piece of wood).
I am wondering if any of you have had any experience in this area?
The manway consists of a door that self seals under the pressure forcing it against the ring that is welded into the head.
My question is: Can this welded ring which is a reversed flange be machined from flat plate? Or must it be forged?
ASME VIII Appendix 2 says Hubbed flanges can't be machined from plate but I can't find any reference to welded slip on or slip in flanges.
The material is strong enough with and across the grain to pass the design. However my 3rd party design appraisers give a reason of fatigue in that if there are imperfections between the elongated grain structure then these may grow and the flange will split (like a piece of wood).
I am wondering if any of you have had any experience in this area?





RE: Flanges Made from Plate Material
RE: Flanges Made from Plate Material
RE: Flanges Made from Plate Material
RE: Flanges Made from Plate Material
ASME and PD 5500 say plate can't be machined 'Weld Neck/Hubbed' flanges due to potential risk of lamination. It says nothing of plain flanges. I'm thinking my design appraisers are being extra cautious and excluding plate for all flanges.
This is more of a metrology/fatigue question.
RE: Flanges Made from Plate Material
Does the arrangment really matter?
RE: Flanges Made from Plate Material
RE: Flanges Made from Plate Material
Cheers,
gr2vessels
RE: Flanges Made from Plate Material
I agree with everything you say. Rolling plate into a ring is fine.
I should have written a better description in my first post. This flange in question is to be machined from 130mm plate without any forming. It is apparently less expensive.
RE: Flanges Made from Plate Material
RE: Flanges Made from Plate Material
If you are to read ASME VIII and PD 5500 they both specifically specify that you can't machine hubbed flanges from plate (due to the thin hub possibly laminating). Surely in the same section there would be atleast some mention of plain flanges or studded pads and any limitations with using plate as opposed to forging.
The example flange I have put forward is quite thin like a hub so should be a forging where as wide flat flanges have more in common with a blind flange which is typically plate.
Engineering judgement.
RE: Flanges Made from Plate Material
RE: Flanges Made from Plate Material
But now that I re-read your original question, I think I might have been confused as to which part we're talking about. You're talking about machining the reverse flange in the vessel wall, not the door, right? So it only sees compressive stress? If that's the case, then I take back my last post. You don't get much fatigue damage under compression.