Compression of Compressed Fibre Gaskets: Is it Linear?

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Discussion Overview

The discussion revolves around the compression behavior of compressed fibre gaskets in the context of bolting torques for flanges on a large water pipeline. Participants explore whether the relationship between applied stress and gasket compression is linear or more complex, as well as the implications for ensuring proper sealing under operational conditions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant questions whether the amount of compression in gaskets is directly proportional to the applied stress, suggesting that the relationship may be more complex than linear.
  • Another participant notes that typical gasket materials are uniform but emphasizes the importance of following specific torque sequences in applications involving bolt patterns.
  • It is mentioned that some gasket assemblies utilize "torque to yield" bolts, which maintain compression through a stretching mechanism, and that these bolts must be replaced if disassembled.
  • A participant expresses the need for stress/strain (compression) curves for different gasket materials to model the effects of gasket compression and recovery during operation, highlighting the lack of readily available information from vendors.
  • Several participants provide suggestions for sources of gasket material specifications, including links to vendor websites and specific product information.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether the compression of gaskets is linear or more complex. There are multiple viewpoints regarding the behavior of gaskets under stress and the availability of relevant data.

Contextual Notes

Participants mention limitations in testing capabilities during the design phase and the proprietary nature of some gasket material data, which may affect their ability to model gasket performance accurately.

James3849
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Hi All,

I am currently researching required bolting torques for flanges on a large water pipeline, but my question relates to compression of compressed fibre gaskets.

I know that catalogues and vendors typically specify the percent compression under a specfic test stress, and also percent recovery. What I would like to understand though is, is the amount of compression directly porportional to applied stress (i.e. linear) or can we assume this is so, or a is it slightly more complex?

I need to know this to ensure a proper seal in the flange, espcially under full pipeline operation.


Cheers
 
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i do not know and it varies...typical gasket material is uniform. but..in any gasket application involving bolt patterns there is a specific torque sequence. on a cylinder head it is a cork screw pattern starting with the bolt located in the center of the head and spiraling outward. i recommend you measure the gasket thickness and tork down the gasket to actual specs. unbolt the assembly and measure the gasket for crush.
 
some gasket assemblies use "torque to yield" bolts. they maintain the proper compression on the gasket by being in "stretch mode". these kind of seals require the replacement of the bolts if disassembled. additionally, many gaskets are not a single material, but a sandwich of multiple layers. the layers composition determine its compression requirements.

dr
 
being in the design phase of the project, we don't really have the luxury of testing gaskets for compression at different bolt torques. We are currently undertaking an investigation into selecting the most appropriate gasket for the job and need to model effect of gasket compression and recovery during full operating conditions.

what would be extremely useful would be stress/strain(compression) curves for different gasket materials.

although from what I've found from vendors, they don't have this information readily available as they tend to deem it proprietry knowledge.

Does anyone know where I could find any characteristic curves for gaskets, particularly for compressed fibre gaskets?
 
Flexitallic has a lot of information. I design high temperature equipment and use a lot of their thermiculite gaskets and the spiral wound gaskets.

Here is some information on the compressed fiber gaskets.

http://www.flexitallic.com/pdf/broCompFiber.pdf

Also, regarding bolt torque see the ASME (American Society of Mechanical Engineers) section VIII division 1 or 2 for their method of flange design.

Thanks
Matt
 
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