Thickness calculation of ovale/obround tube?

[David1974]

I have the flowwing problem:
The circular tubes are formed with rolls to have an oval or obround form .. The final form is not circular but obround. My question according to which formula could I calculate the thickness of these tubes ?

 

[David1974]

of course I want to carry out the thickness calculation according to ASME code

 

[Duwe6]

Only thing that comes to mind would be Finite Element Analysis.

 

[racookpe1978]

How accurate do think you need to be in your theoretical program calculating theoretical strength? Theoretical flow? Theoretical volume? Theoretical interior volume?
How accurate do you think the actual pipes (tubes) will really be made?
How consistent do you think the total group of tubes will be fabricated?

 

[metengr]

Thickness for internal pressure or structural-loading purposes? If the tubes were manufactured incorrectly, they cannot be used for a boiler setting based on most standards for code of construction.

 

[chicopee]

Here is an article that deals on this subject: Oval Pipe a Non-Linear Problem by Andrew C. Whyte, BSc, MSc, CEng, M.I.Mech.E., Copyright August 2001; Web site:

http://www.acwhyte.fsnet.co.uk

 

[JStephen]

If it's an obround form, see Appendix 13 of ASME B&PV Code Section VIII-1.
If you are physically running round pipe through a roll and flattening the sides, the exact shape may be rather indeterminate.

 

[David1974]

The tubes are obround and they are rolled to form a coil of Heating water Boiler ( ASME Section IV)

@JStephen : it´s obround form but I thinck that App.13 is only for vessel and not for tubes !!
@chicopee : if I use the article for the thickness calculation what about the bend calculation ?
@metengr : Thickness for internal pressure.

here is the coil final form

it will be added to the Heating Boiler

http://method-estate.com/wp-content/uploads/2012/02/image75.png

 

[chicopee]

My problem with your OP is that you offered a partial description of the problem. You did not indicate that you have a coil condition. The article deals with straight pipes and I found by perusing the internet. I suggest that you do the same

 

[GenB]

most tank-less boilers/water heaters come with formed tubes these days.


There are no rules that can proof suitability. Proof test is the answer, I believe that is n o other way.
GenBlr

 

[desertfox]

Here is a formula for the wall thickness of an oval tube

http://www-eng.lbl.gov/~shuman/NEXT/MATERIALS&COMPONENTS/Pressure_vessels/ovality_stress_tubes.pdf

I am not sure how you account for the coil but I would start and solve one bit at a time, so check the wall thickness to begin and try to find what effect the coiling might have and then readjust the thickness if required.

 

[GenB]

David's tube is not oval nor obround, Its been flattened rectangular.

 

[David1974]

Thank for your reply ...
The tube is obround ..und the calculation are according to ASME IV