Mimimum flange thickness under a bending moment 1

[ElRak]

Hi everyone,

I’m designing a round post made out of several sections. Those sections are joined together by a round flanges like plates attached together by 10 bolts. The problem is that I can’t seem to find anything regarding the minimum thickness of a bolted flange under a bending moment.

The only thing a found was a formula in a structural book to calculate the thickness of a plate welded to square beam and attached to a wall by 2 bolts. Sadly this equation doesn’t apply well to my situation and gives me a thickness that is way too conservative.

I know that there’s probably an ASME standard for this, I’m just not sure witch one…

Thx

Someone once told me "A black hole is where God divided by zero!!". Yet my old dynamic professor keeps teaching, year after year, the simple fact that you just can't push on a rope. -Engineer

 

[GBor]

Look for information on pipe flanges. Your "pipe" may be solid, but the bolt and flange calculations should still apply.

 

[C2it]

Have a look at

http://www.pipemill.com

This software handles flange calculations under pressure and / or external loads, in acordance with ASME codes and European design codes.

 

[dvd]

While you're at it you might want to calculate the fastener size and number.

 

[carnage1]

The only thing I have to add is to remember to calculate your fatigue strength where the flange intersects the post based on your geometry.

Luck is a difficult thing to verify and therefore should be tested often. - Me

 

[proinwv2]

Take a look at ASME Sec VIII Div 1 for some guidance

Paul

http://www.ostand.com

 

[TGS4]

proinwv2 - Section VIII, Division 1 (and I think that you are referring to Appendix 2), provides absolutely zero guidance on how to deal with external bending moments on flanges.

ElRak - ASME is not where you want to look - they are concerned with pressure primarily. Your situation does not have any pressure. Therefore, any answers that you get from an ASME standard are going to be VERY conservative for your situation.

 

[ElRak]

Thanks everyone for your help...

soooo I've done some digging on my own and this is what I found...

TGS4 you are right, but proinwv2 isn't completely wrong nether. you see Section VIII, Division 1 does not take account of external forces, but Section III does :

"The formula from ASME III for converting external forces & moments on a flanged joint to equivalent pressure is as follows:

Peq = (16*M)/(pi*G^3) + (4*F)/(pi*G^2)

Where:

Peq = equivalent pressure, psig
M = bending moment applied to joint due to weight & thermal expansion, in-lbf
F = axial force applied to joint due to weight & thermal expansion, lbf
G = diameter at location of effective gasket load reaction, in."

if you what to read more on this, check thread378-18541 : Flange Bending Moments.

Using the value of Peq and Division 1, appendix Y (with some minor changes)I did manage to find a reasonable thickness for my "flange like joint". It is still a little conservative, but until I find exactly what I'm looking for, I'll leave it as is. Better safe then sorry...

BTW...here's a link to a mathcad version of the appendix Y worksheet :

http://esce.freeservers.com/

and this is for a very useful site, Xcalcs.com :

http://www.xcalcs.com/

Thx again...

Someone once told me "A black hole is where God divided by zero!!". Yet my old dynamic professor keeps teaching, year after year, the simple fact that you just can't push on a rope. -Engineer

 

[chicopee]

Hey! hold on amigo, you forgot to include external moments on the pipe sections.

 

[ElRak]

chicopee - Not sure what you mean exctly, but the bending moment that I used in the equivalent pressure formula comes from external forces acting on the post, like the wind for exemple.

Someone once told me "A black hole is where God divided by zero!!". Yet my old dynamic professor keeps teaching, year after year, the simple fact that you just can't push on a rope. -Engineer