Ellipsoidal V.S Torispherical

[farzam]

Dear All,

I have a vessel with ID=3500mm,DP=55barg, DT=300c,my recommendation for head is 2:1 ellipsoidal but our fabricator considered an approximation based on UG32(d)with knuckle radius0.17D and a spherical radius 0.9D.Thats acceptable but for thickness calculation he has applied 0.9D instead of D at ellips. formula.whats your idea?is it correct?and why?

Thank you very much

 

[prex]

No, of course it isn't correct.
D is, as defined in UG-32(c), the inside diameter of the head skirt, and stays as such. The approximation permitted in UG-32(d) is only a matter of how to fabricate the head and of checking its shape, the calculation stays exactly as if it was an ellipsoidal.

prex

http://www.xcalcs.com

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[farzam]

Dear prex

I asked him about this matter and the fabricator clarified that he applied K=0.9 in the ellips. cal. formula with the specified h.is this a correct answer?

Thanks

 

[prex]

All they have to do is apply the code formula.
By the way there is no h (height?) in the formula, so can't understand what they are doing.

prex

http://www.xcalcs.com

: Online tools for structural design

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[farzam]

Dear prex,

depth of head (h) is 958mm.

Thanks

 

[prex]

So it is not a 2:1 ellipsoid, as the depth would have to be close to 1750 mm.
Can't comment anymore without some clear and complete data.

prex

http://www.xcalcs.com

: Online tools for structural design

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[prex]

Sorry, the depth would 875 mm of course.
As this head is deeper than a 2:1 ellipsoid, it may be true that its thickness is lower, but to prove this according to the code the correct procedure is in 1-4.

prex

http://www.xcalcs.com

: Online tools for structural design

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads