ASME Flange Calculations

[wlcmech]

I have a flange that has 4 presuure taps drilled from the OD of the flange through to the ID. Does anyone know a reference showing how to verify this arrangement and its application in a ASME Section VIII Div1 pressure vessel design? I am more concerned how to account for the loss of material in the flange calculation. This is no longer a standard Appendix 2 flange calculation.

 

[arto]

If they're small & central they should have minimal effect.

In effect, the flange analysis is like the "Ring Rolling" case in Roark, S = MR/Z, where Z is the section modulus of the cross-sectional area.

You could ratio the Zplain to Zw/hole & account for the increased stress that way.

 

[wlcmech]

Thank you Arto,

The hole sizes are significant. The flange is a 2"-300lb with (4) 0.6" holes drilled tangent to the inside bore. I will look at the Roark Case but I think because the holes are not radial from the center this case may not apply.

 

[prex]

I concur with arto's position.
The worst condition would be with radial holes.
Even if the holes had a diameter equal to half the flange thickness, the stress increase as suggested by arto would be only some 15% (assuming of course the holes are at mid thickness).

prex

http://www.xcalcs.com

Online tools for structural design

See

http://www.xcalcs.com/docs/symbolinfo.htm

if you want to use symbols on these fora

 

[mgp]

Just one comment

A 2" 300# orifice flange to ASME B16.36 have thickness 22.4mm which is the same as a normal ASME B16.5 flange.

This also indicates that you don't have a problem.

regards
Mogens

 

[unclesyd]

As a matter of curiosity what is the temperature and pressure of your system?

We used similar systems except that we used a Dutchmen in lieu of drilling the flange. If my memory serves me right we used a 2" thick Dutchmen with 6" Sch 40 304L SS pipe with a 300 class flanges with (6) .75" dia. tangential nozzles in the Dutchman.
One caveat is that in one of the systems I found differential thermal fatigue in the flange and pipe downstream of the Dutchmen after only three months operation. The temperature difference between the streams varied between 75°F and 100°F.

 

[GenB]

1-You have to tell what you are doing with the flanged connection.
2-so you are using a 2in std flange but you re-bore the bolt connections closer to the id?
please specify.
ER

 

[mgp]

Roca

Please send your comments, however you may not have the latest version so it is possible that the error already have been corrected. You can download the spreadsheet from this site:

http://www.mxl.dk/Download Files/Flange Calculation.htm

This was also mentioned in thread378-83452

Regards
Mogens

 

[mgp]

Just to avoid confusion about my reply above.

This was in response to Roca but his posting has since been removed (and I was instructed by the administrator not to include e-mail adress in replies).

Regards
Mogens

 

[roca]

Mogens
Thanks
I have replied to your address
Regards
Roca