Flange calculation
Flange calculation
(OP)
Dear All,
I have a vessel (12")with body flanges I selected the flange acc. ASME B16.5(Temp-Pres.)but our client asked me to perform flange calculation acc. ASME VIII-App.2!! I specified standard flanges acc.B16.5 so i do not see any requirement to follow App.2
please let me know your opinion
Thanks in Advance
I have a vessel (12")with body flanges I selected the flange acc. ASME B16.5(Temp-Pres.)but our client asked me to perform flange calculation acc. ASME VIII-App.2!! I specified standard flanges acc.B16.5 so i do not see any requirement to follow App.2
please let me know your opinion
Thanks in Advance





RE: Flange calculation
I would ask the client to motivate their request: it might be justified by some special conditions (e.g. external loads, but of course you should be aware of them).
prex
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RE: Flange calculation
Regards.
RE: Flange calculation
For such conditions it is often done that an equivalent pressure is deteremined from the axial force and bending moment. This procedure is described in ASME Section III (I forget the paragraph) and in a number of vessel design handbooks. For example, see the book by Dennis Moss, Appendix G. The equivalent pressure is added to the design pressure and static head to determine the required flange rating.
RE: Flange calculation
If they are looking for calcs for external loads, wind, seismic, etc this is not covered in Appendix 2.
RE: Flange calculation
if your body flange is Girth flange, you have to calculate as App.2 based on load and gasket characters(dimension/y/m).
RE: Flange calculation
Here's the short version,
If your 12" body flanges do not have to resist any external loadings such as wind/seismic/piping loads you can simply use b16.5 ratings. like it is high in vessel with no pipe outlet or used as a top access.
If it is lower in the vessel and has pipe loads in nozzles above it, or there is wind or seismic loads you should use appendix 2.
you often have to use a rating above the standard b16.5 and a thicker hub. But it is still easier than a custom machined flange
RE: Flange calculation
Regarding going to the App. 2 calc, nowhere does that calc include for external bending moments of axial forces. So, using that calc wouldn't be of use - as as mentioned by prex, above, may show that you have a problem, when you really don't.
If your issue is worrying about leakage of the body flange under external bending moments, crank-up the bolt pre-stress (start@ 50ksi assembly bolt stress, and keep increasing it until you have no leakage). Stay below the bolt yield stress, by a reasonable margin - at least 10-15% due to scatter in the bolt stress caused by the assembly technique.
Don't worry about the strength of the flange - this paper http
RE: Flange calculation
The girth flanges per B16.5 can see any of the mentioned external loads, converted into equivalent pressure. Add this to the design pressure and make sure they do not exceed the flange rating (pressure / temperature).
It's really not that complicated.
Cheers,
gr2vessels
RE: Flange calculation
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RE: Flange calculation
Not cover last week in the course by Kan in Houston Div 2
Thank you
Steve Thill
RE: Flange calculation
RE: Flange calculation
Cheers,
gr2vessels
RE: Flange calculation
Let's just step back and look at this case from common sense. This is a 12" dia vessel using a 12" flange; it does not matter if it is used as a body flange or a nozzle flange. It might as well be a 12" pipe. Does everyone do a bunch of Appendix 2 calculations on all piping flanges? No. The argument of wind loading on the body flange don't add up either unless this body flange used to join another tall segment of vessel shell. This is stretching a bit of assumption are we not?
If a client insist on forcing you to do an Appendix 2 calculation then do it. No argument needed. Just give him the cost adder for machining a set of flanges to meet Appenix 2 when the ASME flange don't meet Appendix 2 criteria.
RE: Flange calculation
Cheers,
gr2vessels
RE: Flange calculation
RE: Flange calculation
RE: Flange calculation
RE: Flange calculation
Free download from internet 'Modern Flange Design Bulletin 502" by Taylor Forge (J. Hall Taylor).
Cheers,
gr2vessels