ASME Sect. VIII - Flange Calcs

[cocky2001]

1) If I run the Sect. VIII appendix 2 calcs on a standard B16.5 flange, can I use it for a higher temp/press rating? Vessel design conditions are 200psig & 650°F, but B16.5 says that for a 4" flange (SA-105) at 650°F the pressure rating is only 125psig. I have done most of the calcs by hand and all looks good. Any thoughts?

2) Does anyone have a Mathcad or excel doc to plug the numbers in to do flange calcs?

 

[vesselfab]

That will work...but what about flanges tie in the vessel?

wouldn't it just be easier to use 300# flange.

If I were building this vessel, I certainly wouldn't go to the trouble of checking the flange w/ ap 2

 

[cocky2001]

Yeah, it would certainly be eaiser to use 300# flanges but then I would have to change the Product Manager's mind. And I think we all know the difficulties of changing Marketing's mind.

Thanks for the help.

 

[TGS4]

I suppose that there is nothing that is strictly wrong with what you are proposing. Be forewarned, however, that some B16.5 flanges will fail the Appendix 2 calculations for the rated pressure.

Of course, I guess that you could find the flange that does fail the Appendix 2 calculation, and then you would have "proof' to change the Product Manager's mind.

 

[unclesyd]

Try a 3" or 8" flange.

Always use the worst case gasket seating stress in calculation as someone will use this type gasket.

If you are pushing the limits of a flange you are asking for trouble as someone will tighten the flange until "cups" and leaks. The scenario is normally a small leak and someone over tightens the studs to stop the leak and gets a bigger leak.

 

[eliebl]

It should be noted that if you are going to pursue this route then the B16 designator will have to be removed from the flange. If it remains then the assumption will be that the flange is B16.5 and cause problems with maintenance later in the life of the vessel.

 

[AIOR]

Using 300# standard flange is definitely a better practice. Your non-standard flange will cause changes in the drawings and calculations. It may not in compliance with the customer specification and will need customer approval. This issue needs to be addressed in the Manufacturer's Data Report. Finally, the flange nonstandard marking may cause unnecessary questions at installation or at subsequent repairs. Another scenario: this flange is found at an accident investigation and may bring troubles to your company. As for your Project Manager, well, talk to your QA. To be successful in the market, your company must have a policy of complying with the Code and of satisfying customer and AI requirements, not the Project Manager's.

 

[22west]

FWIW - you can double check your numbers here :

http://www.xcalcs.com/cgi-bin/tutti/x2calcs.cgi?b=i_3_2_0&l=en&s=b&y=0&p=&d=i_3_2_0_0&s=b&y=0

You get a 24 hour free trial.