Max Bolt Spacing Design
Max Bolt Spacing Design
(OP)
I have looked through the ASME B&PV for this, but no luck.
I have a capscrewed metal-metal joint that has an outer diameter and inner diameter bolt circle with pressure applied between bc.
I am looking for a reference that relates the applied pressure, flange thickness and material, bolt size and pre-load, and bolt spacing to prevent deflection/leakage.
I have lots of info about stresses, but the SPACING aspect is confusing me.
Thanks in advance.
I have a capscrewed metal-metal joint that has an outer diameter and inner diameter bolt circle with pressure applied between bc.
I am looking for a reference that relates the applied pressure, flange thickness and material, bolt size and pre-load, and bolt spacing to prevent deflection/leakage.
I have lots of info about stresses, but the SPACING aspect is confusing me.
Thanks in advance.





RE: Max Bolt Spacing Design
My experience has shown that the flange and gasket calculations in ASME VIII gives very stiff and effective joints. They do include all metal joints. A stiff bolt joint is essential so that it never looses preloading.
You could do a FEA analysis on your design to determine deflections. I have not done a metal to metal joint so my thoughts are merely a starting point.
I'll be very interested to see the others comments on your question
Paul Ostand
www.ostand.com
RE: Max Bolt Spacing Design
Maybe question needs a little clarification for others -
This is a semi-circle component with OD, ID, and splitline bolts.
No sealant or gasket between component and the case it is fastened to.
ASME VIII MA 3, Art 3-3 Flanges with Ring Type Gaskets discusses required bolting, but I cannot find guidance that limits the separation/spacing of the bolting based on plate thickness. It tells you roughly how many bolts you will need based on tensile stress area.
Flange Rigidity in paragraph 3-395 - I may use it to "prove" that the design is "sufficiently rigid to control leakage" - but it has gasket factors in the calculation........and I'm not sure how to relate my case.
I also have to modify the ASME equations since they treat the flange as 360 degrees round - and I have a semi-circular shape.
RE: Max Bolt Spacing Design
RE: Max Bolt Spacing Design
Regards,
Mike
RE: Max Bolt Spacing Design
Taylor Forge "Modern Flange Design" Bulletin 502 contains the following:
"When the condition is encountered where a very few bolts will satisfy the requirements of safety but will result in bolt spacing so wide that leakage may occur, it is necessary to adjust the design either by increasing the flange thickness, increasing the number of bolts, or both. The effect that must be achieved is to permit the flange to apply sufficient loading on the gasket between bolt holes to provide a tight joint. It has been found that application of the following gives excellent results:
Bolt Spacing (Max) = 2a + 6t/(m+0.5) "
Where "a" is Nom Bolt Diameter, "t" is flange thickness, and "m" is the gasket factor. For soft flat iron or steel, basically, max spacing is 2 nominal diameters plus flange thickness.
This equation does not relate Applied Pressure, but I suppose that used in conjunction with calculations for required bolt loads (which do account for forces) it should be sufficient.
Thanks for heading me in the right direction.
RE: Max Bolt Spacing Design
Software....for sale. There are some free papers on this site.
RE: Max Bolt Spacing Design
Regards,
Mike
RE: Max Bolt Spacing Design
Paul Ostand
www.ostand.com
RE: Max Bolt Spacing Design
http://www.asmeconferences.org/PVP07/
RE: Max Bolt Spacing Design
Round it up to the nearest multiople of 4, then you can straddle centerlines. {i.e., go to 12 bolts for the 10" BCD}