choosing shape of head
choosing shape of head
(OP)
What kind of consideration when choosing either semi ellipsoidal or thorisperical head for a pressure vessel? It would be use as Knoct Out Drum. Also the advantage & disadvantage of them.
This matter is regardless cost or fabrication schedule. It's pure technically assistance.
This matter is regardless cost or fabrication schedule. It's pure technically assistance.





RE: choosing shape of head
(personally, I prefer working with semi-ellipsoidal heads, those special design rules in ASME Code for torispherical heads always trip me up and annoy me)
RE: choosing shape of head
RE: choosing shape of head
RE: choosing shape of head
Yes. Toripherical heads are typically called F&D heads.
F&D heads have smaller knuckle radius. We don't want high nozzle load causes head buckling.
RE: choosing shape of head
RE: choosing shape of head
You won't find a code or standard that answers your question. Codes and standards are about minimum requirements, not common design practices or good engineering judgment.
If you wanted to pay for the extra steel, you could put a torispherical head on a Section VIII Div. 1 vessel designed for 750 psi. The reasons not to do it are non-code reasons.
jt
RE: choosing shape of head
One consideration with using F&D heads is that you have excess plate thickness in the crown area that can be used for reinforcing if you know you'll have nozzles or manways there.
RE: choosing shape of head
A couple of small things not mentioned above:
- F&D means "flanged & dished"
- ASME VIII has specific dimensional requirements (knuckle radius)for various heads. (I am not sure about other codes) Be careful if purchasing a head; you might get one that cannot be used for the code you choose)
- "80:20 heads" are an ASME code qualified compromise shape that exists to minimise material usage. Dimensionally, they are kind of fit "in between" ellipsoidal and F&D heads. They are sometimes specified for larger diameter heads made of more exotic materials.
Just my two cents....
-MJC
RE: choosing shape of head
james1 – IMO your statement that pump / agitator nozzles should not be located on a torispherical (F&D) head is not correct. There are torispherical heads – as MJCronin has pointed out – that are close to 2:1 ellipsoidal in shape. I think you are sticking to the 6% minimum knuckle radius limit. It all depends on the load applied to the head, the head thickness used (of course). I have used several torispherical ends in the past supporting agitators with no issues whatsoever.
Check this link – from memory I believe that these are not 2:1 DE's on these glass lined reactors. http:/
RE: choosing shape of head
regards