O ring application guides

[Cliff897]

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[bendavanza]

great resource, thanks!

 

[Bobby_M]

Are you actually making a case for using Buna N over silicone in brewing applications or is it just a generic Buna-N Oring appreciation piece?

I can tell you for sure that I've had success using #417 silicone rings for temperamental corny lids where the Buna failed. I also like them on the posts much better because they're softer in the cold.

The cost portion is a little silly at the homebrew level. We're talking about a difference of a few dollars for a lifetime supply.

I appreciate the links to the resources.

 

[DrDirt]

you spent an awful lot of time thinking about o-rings.

 

[schmagy]

Buna is a wonderful material, however i can tell you from 15yrs experience in the hydraulic industry that although buna will seal for 300 hours at the 149 you referenced. I can guarantee that the test was not conducted during heat cool and disassembly cycles.

Buna begins to harden at 149 degrees and will start out at around 70 durometer and harden quickly. it will take a set at a time value MUCH lower than 300 hours and begin to develop cracks somewhere in 150-200 hour range. eventually the seal becomes so brittle that it crumbles away and the seal fails.

In any situation where heat is applied above 150 degrees and or there is dynamic movement due to disassembly or simply thermal expansion contraction differences of metals viton/fkm or silicone will hands down win durability and performance.

Silicone is used in food and medical due presumably to its chemical and biological properties.

I prefer viton for durability but dont see it in food and packaging applications or medical, so i wonder if there is a problem there with food safety...

Cost is certainly an issue, however lets get real.
any joe blow repair shop can buy direct from any of a number of manufactures including sealsource in portland:

http://www.sealsourceinc.com/products.html

Hercules Hyd in florida or a host of others.

List prices directly from sealsource published catalogs for orings for a corny keg in buna viton and silicone

-111 seal .05 .23 and .32 cents respectivly
-109 prices are the similar
-417 main 1/4 inch seal was P.O.R. but a larger seal was $1.10 $8.54 and $7.14 respectively

In the scales that even a larger hombrew shop would order, the shipping would likely cost more than a bag of seals.

 

[schmagy]

Softer 70 durometer buna, soft silicone and other soft materiels will seal better in a low pressure environment found in corny kegs. Especially when dealing with bent and ill fitting lids.

 

[Cliff897]

Are you actually making a case for using Buna N over silicone in brewing applications

Yes.
While I can't (& wouldn't try to) tell you that Silicone is bad, I can tell you that Buna N is good and lots cheaper and lots tougher than silicone.
Buna N is however, not a pretty as silicone.

 

[Cliff897]

you spent an awful lot of time thinking about o-rings.

Well, yes, I have been involved in O rings a very long time. Before I went to law school and after almost 2 decades as a machinist toolmaker, I was employed variously in engineering R&D, working on things like the MX, the Hubble, NASA, a stint with a university UHV physics research lab, and a decade as head of R&D for a laboratory apparatus company.
All along the way O rings were very important.