Fastener spacing and sealing with o-rings

[greentlc]

I have to seal a spherical container comprised of 2 hemispheres joined together with a bolted flanged connection. I plan on using o-rings to seal the liquid (water) in. The problem I am having is finding the minimum number of bolts required to compress the o-ring and seal the joint. Can anyone point me in the right direction? Any help is appreciated.

Thanks

 

[huntoon]

How much pressure do you anticipate? What is the area of your flange surface?

 

[huntoon]

try this:
http://www.krrao.com/images/ASME_Ch40_p001-036_11-14-08.pdf

 

[greentlc]

I'll check that link out. To answer your question, the internal pressure is about 125 kPa and the flange area is 0.061 m².

 

[huntoon]

just curious, why do you need the minimum amount of bolts?

for theory?
for cost?
for weight?

 

[greentlc]

huntoon,

I am mostly going through the through the calculations for theory as it is for a school project. I was just trying to factor in the force required to keep the o-ring in compression with the internal pressure working to un-seal the joint. Using this I was going to calculate the number of bolts around the bolt circle. Is this not usually done, or is it done by different means? Thanks again for the help

greentlc

 

[peterlonz]

A conventional & quite normal engineering approach to this question, would be to select one of the many Standards documents which deal with sealing flanges at various pressures, with appropriately chosen safety factors.
Be aware that your O ring should be only ever subject to minimum compression within it's elastic deformation range. Any O ring supplier can provide charts advising on this. Remember that O rings will almost always be seated in O ring grooves which are also subject to close specification by the O ring suppliers.
Your bolt spacing will probably be commanded by the flange thickness & available surface area to accommodate the bolt heads.