Annular Pressure Vessel with flat plate ends

[MikeC88]

Hi all,

I am a first time user of BPVC VIII and am looking at an annular pressure vessel with flat closing plates, ref attached hand sketch.

I have determined the following codes are to apply to the rolling's:

UG-27 - Outer rolling subjected to internal pressure
UG-28 - Inner rolling being subjected to external pressure (Length for calcs based on length between half thickness of front and rear closing plates

The advice I am looking for is what is the best section to apply to the flat closing plates that are causing a bit of an issue, do I:

1) Treat situation conservatively and assume the flat annular plate to be a full width unstayed flat plate, and apply UG-34 (I imagine this is worst case due to increased surface area & lack of support in centre)

2)Utilise UG-47 or UG-53 and assume single centrally located stay bar/ligament (if it is possible to treat in this manner)

3)Utilise another section of the code, Perhaps Mandatory Appendix 13 13-13(?)

I was going to base the closing end calcs on the annular closing plate, and then apply the same thickness to the front plate.

Also if anyone has any further advice on this I am all ears, to note I realise these calcs do no cover corrosion/structural requirements and these need to be considered separately.

Thank you in advance for any assistance/advice offered.

Cheers,

Mike

 

[racookpe1978]

You show only an OD and ID as labels, no dimensions in the sketch. Your assumptions for the bending may be correct for some lengths and some heights of the plates, and will be terrible for shorter (smaller) distances. What are the actual OD, ID, wall (plate) thickness and heights?

 

[TomBarsh]

One "interesting" characteristic of the inner cylinder of an annular pressure vessel is that internal pressure in the chamber imposes circumferential compression simultaneously with longitudinal tension. This is not the condition considered by the basic rules of ASME BPV UG-23 and the vacuum charts of II-D, where both directions are compression.

I actually worked on such a vessel. A fairly large (24 ft diam x 68 ft tall) low pressure/very high temperature vessel intended to be used for in-situ annealing of nuclear reactor (after rods were removed). It was built, don't know if it was ever actually used, it was sort of experimental. I do remember the inner cylinder and its quirks. I don't remember how we resolved that, it's been over 20 years ago.

For the (apparent) relatively short span of the internal cylinder in your sample file the effect of the compression/tension fields probably will not be too extreme (unlike our case with a much longer span between bracing).

 

[racookpe1978]

That's what I was trying to emphasize: What are the real dimensions and thicknesses? Without knowing that, you CANNOT make the assumptions to start the solution.

 

[MikeC88]

Hi All,

Thanks for the quick responses, apologies on not adding dimensions,

Hopefully the below will give an idea:

ID outer Rolling = 540mm
Annular OD= 175mm
Height of vessel = 50mm

Plate Thicknesses, as they stand:

Rolling's: 6mm
Front plate & Annular plate: 12mm

Very Interesting point TomBarsh on the longitudinal tension, I can certainly see it being an issue with much taller vessels, this is much smaller and so I think may be less of an issue.

 

[SnTMan]

Well, a little off the point, but I see more corner joints than butt-joints. MikeC88, see UW-13 regarding design of the same.

This is generally not a straightforward Sec VIII Div. 1 design. It's more a U-2(g) design.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[MikeC88]

Mike,

Thanks for highlighting those points I will review and see where I get to.

Cheers,

Mike

 

[racookpe1978]

please confirm what is the ID and height of rolled 6 mm plate UG-28 in your sketch, and what is the height of the 6 mm rolled plate UG-27, ID = 540 mm. Is that taller one UG-27 the 50 mm height?

How is the rolled plate UG-27 supported? Is it free to move (expand) as pressure increases in the annulus, or is it restricted (by something not in the sketch) and so is being bent outwards by forces at the top retrained by the (solid ?) upper plate.

 

[r6155]

Is this little product under the scope of ASME VIII Div. 1 U-1?.

Regards
r6155

 

[MikeC88]

Hi Racookpe,

Apologies on the delay,

UG-28 ID 173mm, height: 50mm
UG-27 Height 62mm

UG-27 is supported by a backing plate not shown in the sketch, the free ends of UG27 in the sketch are to be welded to this. there are no restraints on the OD of UG27 preventing expansion other than the solid plate welded at either end.

Regards,

Mike

 

[MikeC88]

Is my understanding that a U-2(g) design is effectively a design from first principle/Roark/similar such reference applying the same rules for max allowable stress as specified in UG-23/ Mandatory Appendix 1 of BPVCII?