stack flange design process

[nuche1973]

Greetings:
I was involved with the design of a chimney stack. The design calculations were reviewed and it was determined that my flanges are too small. I used AISC prying as the basis for my calculations. However, during the review process the client stated that I need to look at the flange the way a mechanical engineer would see it: as a pipe flange. We are dealing with 1250 k-ft of moment on an 80" diameter stack with 30k of dead load. My question is how does a mechanial engineer design a pipe flange with these conditions? I have a copy of ASME Section 8 that covers pipe flanges, would this be a good starting point?

 

[boo1]

Consider uploading your design and calcs.

 

[MJCronin]

nuche....

Because they are so specialized, the ASME has a publication on the design of steel stacks.

http://catalog.asme.org/Codes/PrintBook/STS1_2006_Steel_Stacks.cfm

I believe that there are many design details contained including requirements on flange design.

Your client has his head up his butt....stack flange designs have nothing to do with ASME pressure vessels or piping.

My opinion only

-MJC

 

[boo1]

Ch 4 design section of the STS-1 can be seen at:

http://www.eng-tips.com/viewthread.cfm?qid=271837&page=1

notes:
Load calculations of the stack’s static response shall account for a minimum corrosion allowance of 1/16” steel shell thickness.

Stack shall provide qty (1) 1” NPT connection for draft measurement and qty (1) 1 ½” NPT connection for flue gas temperature measurement

Four EPA test ports. The test ports must be at least 8 diameters above the last gas flow disturbance and no less than 2 diameters below the stack exit. Ports will be located at no less than 90 deg from adjacent test ports. (Size of test ports and locations must be confirmed with local regulatory agency or testing facility.)

Freestanding stack shall be designed with a false bottom and a minimum drain diameter of 1”

Circumferential reinforcing rings shall be incorporated into the design. No reinforcement members shall extend into the gas stream.

Stack shall be factory painted with a suitable primer for the operating temperature of the flue gas.

The stack design shall incorporate helical strakes to reduce vortex wind loads if required


Additional References:
IS 6533 -

http://www.scribd.com/doc/21067606/Is-6533-Part-1-Design-of-Construction-of-Steel-Chimney-Cod

BS 4076
CICIND -

http://www.cicind.org/EN/index.php

ASME B31.3 and Section VIII of the ASME Boiler and Pressure Vessel Code (if combustible gases under pressure)
ANSI/AIHA Z9.5 –2003 exhaust velocity design guideline

 

[nuche1973]

Thanks, that helps. Now all I have to do is convince the bosses we need to buy the STS-1 code.