Fastener spacing and sealing with o-rings

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Discussion Overview

The discussion centers around the sealing of a spherical container using o-rings in a bolted flanged connection. Participants explore the minimum number of bolts required to effectively compress the o-ring and achieve a proper seal under internal pressure, with considerations for theoretical calculations and engineering standards.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant seeks guidance on determining the minimum number of bolts needed to compress the o-ring for sealing a spherical container.
  • Another participant inquires about the anticipated internal pressure and flange area to better understand the sealing requirements.
  • A link to a resource is provided, suggesting it may contain relevant information for the calculations involved.
  • The internal pressure is stated to be approximately 125 kPa, with a flange area of 0.061 m².
  • Questions are raised regarding the rationale behind needing the minimum number of bolts, considering factors such as theory, cost, and weight.
  • A participant suggests using established standards for sealing flanges at various pressures, emphasizing the importance of safety factors and proper o-ring compression within its elastic deformation range.
  • It is noted that o-rings should be seated in grooves specified by suppliers, and that bolt spacing may depend on flange thickness and surface area for bolt heads.

Areas of Agreement / Disagreement

Participants express varying approaches to the problem, with some advocating for theoretical calculations while others suggest reliance on established engineering standards. No consensus is reached on the best method to determine the minimum number of bolts.

Contextual Notes

Participants mention the need for safety factors and the specifications provided by o-ring suppliers, indicating that the discussion may depend on specific definitions and standards that are not fully resolved in the thread.

Who May Find This Useful

Students and professionals interested in engineering design, particularly in the areas of fluid sealing, bolted connections, and o-ring applications may find this discussion relevant.

greentlc
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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
 
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How much pressure do you anticipate? What is the area of your flange surface?
 
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.
 
just curious, why do you need the minimum amount of bolts?

for theory?
for cost?
for weight?
 
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
 
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.
 

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