EN 13480-3 Flange Calculations 4

[Deepak_johsh]

Hi,

I am trying to Check if a custom flange (Dimensioned Pre-defined by TTMA) meets the requirements of EN 13480-3
But when I do so, I find that the Bolt force is higher in Assembly condition rather than that in Operating condition.
Im looking for answers on how this can be possible?

Because, After a preload is applied to bolts of the Flange joint, fraction of any external load introduced must to taken up by the bolt.
so this must lead to bolt load in operating condition higher than that of Assembly condition.
but with the calculation as per EN 13480-3 this isnt the case.
Could anyone guide me in the right direction please?

Parameters used are as follows:
b = Effective assembly width
G = Diameter of gasket load reaction
y = minimum gasket seating pressure
H = Total Hydrostatic end force
HG = Compression load on gasket to ensure tight joint
HR = Balancing reaction force outside bolt circle in
opposition to moments due to loads inside bolt
circle

 

[goutam_freelance]

Preload bolt forces are trying to close the flanges but the operating pressure is trying to open the flanges. They are trying to cancel each other. So the operating pressure is trying to reduce the bolt tensile load.

 

[Christine74]

In some cases the required bolting area is set by the Gasket Seating condition, not by the Operating condition. Factors that can cause the Gasket Seating condition to govern include low design pressures, small vessel diameters, wide gasket widths, and/or difficult to compress gasket materials such as Spiral Wound or solid metal gaskets.


-Christine

 

[Deepak_johsh]

Thanks for your valuable Insights Christine.
Could you point me to some reference material where i can read more about this please??
I am interested to know more about when (in addition to the factors you've mentioned above) and why Gasket seating Condition govern the design calculations

Thanks again.

 

[Christine74]

Taylor Forge Bulletin 502 would probably be a good place to start. SnTMan uploaded it in this previous thread:

Why Gasket load formula 3.14Gby in Wm2 and why is it 3.14G(2b)m.P in Wm1? - ASME (mechanical) Code Issues

My question is, as per Mandatory appx.2 from ASME Section VIII div.2. Why the area of gasket considered for Wm1 and Wm2 is different? In case of Wm1, the formula is, Where, the area of gasket considered is , 3.14 x G x 2b And in case of Wm2, the area of gasket considered is, 3.14 x G x b...

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-Christine