Eccentric cone with angle 45° (ASME VIII-1)
Eccentric cone with angle 45° (ASME VIII-1)
(OP)
Hello to all,
I have a little problem with one pressure vessel with eccentric cone. (α~45°- see the attached picture)
In UG-32 (g)(2) stands that angle should not be larger than 30°. However, 1-5 (g) say that junctions with angle grater than 30° are allowed but only if design is based on special analysis.
My question is: What is the simplest way to resolve this issue and is the FEM Analysis allowed?
Thank you for your answer in advance!
I have a little problem with one pressure vessel with eccentric cone. (α~45°- see the attached picture)
In UG-32 (g)(2) stands that angle should not be larger than 30°. However, 1-5 (g) say that junctions with angle grater than 30° are allowed but only if design is based on special analysis.
My question is: What is the simplest way to resolve this issue and is the FEM Analysis allowed?
Thank you for your answer in advance!





RE: Eccentric cone with angle 45° (ASME VIII-1)
I have one more question regarding the same vessel.
If the "End of scope" is marked like on the picture, does the Positions 1, 2, 3 have to be made from ASME Materials or are they out?
What is the correct way in this case to interpret U-1 (e) (1) (-d)? Or there is some other rule that must be taken into consideration?
Thank you!
RE: Eccentric cone with angle 45° (ASME VIII-1)
And, accepting your end of scope limit, item 1 is like a flange (out of scope), item 2 is like a bolt (out of scope) and item 3 is like a nut (out of scope). However your detail appears to be a pressure retaining cover, not a connection to an external piping or device per U-1(e)(1), so it should be included per U-1(e)(3).
prex
http://www.xcalcs.com : Online engineering calculations
http://www.megamag.it : Magnetic brakes and launchers for fun rides
http://www.levitans.com : Air bearing pads
RE: Eccentric cone with angle 45° (ASME VIII-1)
Yes, u are right, U-1(e)(3) is clear.
I have a pressure retaining cover (item 2) so it must be included, together with attaching "like a bolt" (item 3) and "like a nut" (item 1).
RE: Eccentric cone with angle 45° (ASME VIII-1)
Conditions:
Material: X5CrNi18-10 (1.4301)
External loads:
Inner pressure: 5bar
Temperature: 50 °C
Fixed geometry: upper surface of cylindrical shell
Criterion: Von Mises
In order to avoid any peak stress in transition area between cone and cylinder i made a round fillet area which represents inner weld and thus is close to real conditions.
Can i make the following conclusion: "Maximum stress appears on the upper edge of cylinder shell and is result of given initial conditions (fixed geometry)."?
RE: Eccentric cone with angle 45° (ASME VIII-1)
prex
http://www.xcalcs.com : Online engineering calculations
http://www.megamag.it : Magnetic brakes and launchers for fun rides
http://www.levitans.com : Air bearing pads
RE: Eccentric cone with angle 45° (ASME VIII-1)
It is a solid element. How can i now detemine bending stress at the transition? (i am using solidworks simulation)
Maybe u have some example?
Is this an answer: http://help.solidworks.com/2014/English/SolidWorks... ?
RE: Eccentric cone with angle 45° (ASME VIII-1)
- your mesh is crap. The fluctuations that you show in your stress plot ought not to be there, and are as a result of a very poor mesh. You have likely used tetrahedral elements - I truly hope that you have used quadratic tetrahedrals, because linear tets are all kinds of bad. I would take prex's advice and use shell elements, but if you are bound and determined to use solid elements, please use hexahedral elements. Ensure that you have a minimum of 3 quadratic bricks in the through-thickness direction, and at least 96 in the circumferential direction.
- do not model any sort of fine fillet radius at the corner. The methodology will sort out the peak stresses.
- cone-to-cylinder junctions often result in compressive stresses, which lead to a different failure mode that is less dependent on the magnitude of the stress: buckling.
- follow the methodology presented in ASME Section VIII, Division2, Part 5. You will need to satisfy ALL of the failure modes: Plastic Collapse, Local Failure, Collapse From Buckling, and Failure From Cyclic Loading: Ratcheting. And you will also need to consider possibly fatigue if you will be in cyclic service. You are performing calculations for an ASME Section VIII, Division 1 vessel, utilizing the statement U-2(g). Although there is not (yet) guidance on how to use FEA to accomplish this, I have written a post that addresses what I believe to be industry best practice in this regard - http://becht.com/blog/performing-an-fea-in-section...
My recommendation to you is that if you have never done this before, either get a good mentor or hire an expert. I would estimate that a design like this would probably take me a day to do, and then another day or two to write up the report, suitable for submission to the most challenging jurisdictions in the world.