Large Opening in Rectangular Vessel

[mxms80809]

I have a rectangular vessel with stiffeners on 3 sides. There is a large non-circular opening on one side (where a heater is mounted on weld studs). I have analyzed the vessel according to APPENDIX 13, but am not sure how to approach the large opening and reinforcement required.

The Vessel is 1/4" 316L SS Plate (all sides)
Stiffeners are L2x2x1/4 A-36
Heater panel is 3/8" 304SS Plate

 

[jehan17718]

mxms80809,

Seeing the geometrical complexity of the attached JPEG file, I feel that you need to view this problem as that prescribed in U-2(g). Design appears to be propriatry in nature. Obviously if so, ensure vendor takes full guarantee of the mechanical design. Btw, is this a u-stamped/ ASME vessel?

FEM would be the most definitive method to analytically design this "box" based on the complex geometry.

Also, what is the internal/ external design pressures and temperatures and MOC of this "box"?

My reply is not too helpful. Sorry about that

-jehan

 

[mxms80809]

jehan,

I am fairly new to the whole B&PVC scene as I just graduated a year ago. Its a complex project that i have been assigned to analyze. This is just a tiny piece of the puzzle. It is not U-stamped but customer has asked we build it with all of the criteria as if we were to get it stamped. I keep getting stumped with the U-2(g)reference. Is it safe to assume I can run an FEA on said section and compare to the 1.5SE or 2/3SY allowables??

internal pressure is 5.2 psi

Thanks

 

[TGS4]

In short - NO. I would highly recommend that if you are going to apply U-2(g), you refer to ASME Section VIII, Division 2. For the 2007 Edition, you will look at Part 5, for the 2006 and earlier editions, you will look at Appendix 4. The rules are complicated (search the archives of this forum on discussions of "Design-By-Analysis" and FEA). I would highly recommend that you find a good mentor for this problem. Failing that, I would suggest that you request your company to hire someone who does this sort of thing for a living and has years and years of experience. Even with an internal pressure of 5.2 psi, if the vessel broke, someone could get killed...

 

[saplanti]

mxms80809,

I can see that that image is more likely a duct and may not be cavered by the vessel design codes.

If my guess is correct the opening requires a structural calculation in addition to flange calculation and sealing check.

You either use stiffeners on the opening cover or on the duct or on both. In case stiffeners used you need to think about the load path, how to take the pressure and gravity loads from the cover onto the duct structure.

Hope it helps.

Ibrahim Demir

 

[LSThill]

mxms80809 (Mechanical)

OPTION 1: Page 53(A)lease look at Page 53(A) detail example

Solutions to Design of Weldments

https://ssl.lincolnelectric.com/foundation/item.asp?prodnum=D810.17&PID=16

8 ½” x 11” Paperback

This design brochure represents a collection of the most frequently encountered design problems experienced by Mr. Blodgett. The text gives sample problems and a solution recommended by Mr. Blodgett. Typical topics include: circumferential welds in torsion, longitudinal shear on 8 sided section, shock loading, and distortion. 78 pages.

Cost $3.50

Design of Welded Structures

https://ssl.lincolnelectric.com/foundation/item.asp?prodnum=DWS&PID=16

Cost $22.00

Design of Weldments
By Omer W. Blodgett, design consultant
This reference handbook describes in detail design techniques for creating machine designs in arc welded steel. Much of this material has had no previous publication. Theoretical analysis, problem-solution examples and case history studies explain how to design machine components for manufacturing economies and improvement of product performance through efficient use of steel’s excellent physical properties.
Since its publication, this book has become a standard reference manual for design problems in welded metal products.

Design of Weldments includes 8 sections dealing with ‘Weldesign,’ a system that reduces weight and cost and improves production.
464 pages, 8 ½” x 11”, 923 illustrations, nomographs, charts.
Cost $15.00

Take the course and get the book's

OPTION 2:

Paulin Research Group FE-PIPE

http://www.paulin.com/

Regard
Leonard Thill

 

[jehan17718]

mxms80809,

I agrre with TGS4 views on using ASME Section 8 div 2 to find out the allowable stresses if you are doing FEA.

Saplanti has also correctly pointed out that it looks like some sort of a ducting element and thus ASME S8 might not be the appropriate code and you positively require the help of some seniors to advise you on this problem. What is the service of this "box"

AS I had asked in my first reply, what is the internal/ external design pressures and temperatures and MOC of this "box"?

-jehan

 

[saplanti]

mxms80809,

I missed the mounted heater at the opening in my first reply. It is definetely a duct and the heater is the duct heater. Depending on the type of the heater and air velocity the heater flange may be heavy rigid element, therefore you do not need any stiffener on the heater side. If it is a large cover plate and Kanthal type tube heaters are in a vertical line you may need to stiffen the cover plate as well. Vibration of the tubes under the air velocity might be another problem to check.
I think you are using the large displacement theory to reduce the duct plate thickness down and therefore you need stiffeners on the duct at top and bottom edges to take the created tension load at the edge and the gravity forces of the heater by the bending stiffness of the edge stiffeners.

I suggest you to think how to transfer the heater gravity load and the internal/internal pressure. In case it is different than the Kanthal type tube heaters, due to the overhang (inside/outside) of the heater the top and bottom flanges of the opening may need good attention. Additionally the sealing will play big role in the flange connection. If you can use the prying action of the flanges of the opening you may be able to keep the selected flange thicknesses, but you still need a calculation to verify.

Hope it helps.

Ibrahim Demir

 

[LSThill]

mxms80809,

If duct Please look at Page 53(A) detail example

 

[LSThill]

mxms80809 (Mechanical)

Vertical Exhust Connectin for turbines

What is this duck being used for if Vertical Exhust Connectin for turbines installation and unrestrained expansoiion joint at the exhaust, an additional amount of force caused by pressure loading. ( The additional force referred ot is perpendicular to the force of the exhaust flange and central.) For this type of applicatin, calculate the verticdal force component on the exhaust connectin, excluding pressure loading, and compare with value of 1/6 the pressure loading on hte exahust. Use the larger of these two numbers for vertical force ocmponent on exhaust connectin in making calculation.

From Korea
Leonard Thill

 

[PVinspector]

To answer this particular question:

I keep getting stumped with the U-2(g)reference. Is it safe to assume I can run an FEA on said section and compare to the 1.5SE or 2/3SY allowables??

Not in Section VIII Div. 1 unless no Code rules exist.You can only use U-2(g) if no Code rules are given, then the obligation is to make is as safe. If Code rules exist (as they do of course for openings) then you must satisfy them as a minimum. The Section VIII Div. 2 advice is excellent as there is much more flexibility for design by analysis there.