pure graphite Gaskets vs reinforced graphite gaskets

[gfernan]

Hi
I would like to know what are the diferences between a pure graphite gasket and a reinforced graphite gasket wich one is better.
And comparing this gaskets with the non asbestos gaskets?
Thanks

 

[MikeHalloran]

Well, the reinforced gasket is less likely to be crumbled between manufacture and installation. ... but it may not be the best gasket for a particular application.

... speaking of which, you didn't mention your application, so any comparison we could make is meaningless.



Mike Halloran
Pembroke Pines, FL, USA

 

[gfernan]

Thanks Mike, the gaskets is for a hot reactor feed/effluent exchanger.
For desing the gasket recomended was nos asbestos, but latter it was changed to pure graphite, Now they are proponing reinforced graphite. I would like to know if this chance can bring any difficulties

 

[MikeHalloran]

It depends on what's in the stuff you're trying to contain.

The reinforced graphite gasket material with which I'm most familiar it called 'tang' in the gasket trade. The reinforcement is a thin sheet of stainless steel with a multitude of tangs pierced and formed normal to the sheet proper, then sort of crimped onto the graphite.



Mike Halloran
Pembroke Pines, FL, USA

 

[SnTMan]

gfernan, a 100% graphite gasket is going to be made of a number of plies of graphite film. These plies will tend to slide across one another and so to exit the joint. I know this firsthand Some means is necessary to retain them. One such is the tanged construction MikeHalloran refers to. Sheet sizes of these are limited. Another such means is applying graphite facings to a metal core, such as so-called Kammprofile and Graphonic styles of gasket. Visit the Flexitallic or Garlock websites to start.

As to non-asbestos gaskets they are, literally, anything that is not asbestos. The term is generally used to refer to composition sheet gaskets which were formerly often reinforced wth asbestos fibers, now more likley aramid or something.

For an F/E exchanger I would personally prefer a metallic, graphite faced gasket, such as the aforementioned styles.

Regards,

Mike

 

[tothepoint]

Limit compressed, non-asbestos fiber gaskets to temperatures <250F (they have lots of rubber in them). Use a reinforced graphite gasket between 250-600F. Above 600F graphite will oxidize with time and create leaks. Foil or tang reinforced graphite sheet gaskets are much better than pure graphite because they increase pressure resistance and provide some rigidity to the gasket, making it less fragile. For exchangers or other cycling service use a corrugated insert graphite gasket (CGM). Be careful of camprofile gaskets as they need extremely flat mating surfaces and do not cycle well; thus requiring high bolt loads to allow the bolt themselves to be the spring in the joint.