Compression of Compressed Fibre Gaskets: Is it Linear?

[James3849]

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

 

[Ranger Mike]

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.

 

[dr dodge]

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

 

[James3849]

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?

 

[Ranger Mike]

go to Mcmaster Carr web site

http://www.mcmaster.com/#gasket-sheets/=4ur7ho

a whole lot of sources for gasket material with applicable specs

 

[CFDFEAGURU]

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