O-Ring groove design

[cadmech24]

Hi,
I want to get knowledge on O-ring groove design.
Can anyone help me in how to decide on particular O-Ring? which table and how it to be used.

Thanks

 

[GregLocock]

Yup. Find and download the Parker O ring handbook.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[unclesyd]

In addition to the excellent advice given by GregLocock you should try to find an older edition of Machinery's Handbook. This book contains all the basic information you apparently need.

 

[Cockroach]

There is a PDF of Parker-Hannifin O-Ring Handbook ORD5700, downloadable from their website.

Parker is an excellent company and fully supports design applications. They had an elastomer program called INPHORM which I believe is still available. Get both the o-ring and polypak editions!

And when it comes to rubber, these guys are the best. I highly recommend earmarking their website. And no, I am not a Parker employee or salesman, but definitely a disciple of that business.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[MikeHalloran]

I'll jump on the pile, too.

Use the Parker handbook.
Do not deviate from it.
The designs encoded therein are already optimized.





Mike Halloran
Pembroke Pines, FL, USA

 

[racookpe1978]

Oh come on Mike!
Isn't always more fun to go off rapidly on your own and invent your very own personal mistakes rather than look up and actually study somebody else's stuffy reference book ... just because they've been doing it for years? 8<)

 

[Cockroach]

International and Apple are alternatives in sourcing the design handbooks in elastomer application. Parker-Hannifin in my humble opinion, as stated, is the best. But you can get decent information from multiple sources, never a bad thing.

Mistakes usually come from departure of receipe values offered by the various manufacturers. I have bastardized several gland specifications based on design problems, so have a very accurate set of equations that govern stretch (known as set) and squeeze (also known as compression). I would recommend the study of these two issues, they govern the reason as to why elastomers perform. Gland geometry is set by "fill".

Also note that there are multiple applications that specify gland depth defined from the seal diameter. The application being static, dynamic, reciprocating or face seal are the four main categories you need consider.

And don't forget the rubber compound, chemistry, explosive decompression, set and degragation given lifetime are important considerations.

Good luck with it.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[Shockdesigner331]

Use the Parker Handbook. Think about using backups with higher pressures. Pay particular attention to the fluid used with a particular compound. Just saying "Nitrile" is not fully specifying a compound. After you pick out an o-ring, make sure you can actually install it! Large cross section o-rings require quite a bit of force to assemble in the gland. Don't use o-rings for reciprocating assemblies unless failure and replacement are acceptable, go with the parker urethane seals, they work great and are cheap - just keep an eye on your operating temperatures.

 

[flash3780]

You may check the SAE Aerospace Recommended Practice for O-Ring gland design (ARP1232). No reason to reinvent the wheel; someone's already optimized o-ring glands.

 

[dgallup]

I have o-ring design handbooks from at least a dozen suppliers. The best one was from National but good luck finding one now. The Parker one is decent but their INPHORM software isn't worth the electrons it's written on.

While I make every attempt at using standard o-ring sizes and gland designs, in reality all the o-ring manufactures produce far more sizes. In particular, the AS-568 series is seriously lacking for small cross section o-rings. How on earth did they think that only 4 sizes were needed with a cross section smaller than 1.78mm? We use 20 different sizes with cross sections smaller than 1.78mm and we are pretty small.

Proper material selection is key to successful o-ring applications. There are an almost infinite number of compounds, Precix has at least 40 standard fluorocarbon compounds and quite a few more specialized ones. Learn how to use the ASTM D2000 / SAE J200 specification for rubber compounds and run as fast as you can from any supplier who can't quote it chapter and verse.

Beware of stockist who say they have "viton" o-rings. Usually this means there is no pedigree and no traceability on these o-rings and they are almost always made in a "low cost country" with a lot of filler and very little fluorocarbon, almost certainly NOT from an actual DuPont Viton(R) compound.

All that said, if you can avoid or eliminate an o-ring it will improve your design reliability and reduce your design FMEA RPN.

 

[flash3780]

All that said, if you can avoid or eliminate an o-ring it will improve your design reliability and reduce your design FMEA RPN.

In my experience, radial o-ring connections are a very reliable method of producing a non-permanent pressurized connection. I've always felt them superior to compression fittings in dynamic applications; it is often easier to provide secondary retention to the threads in an o-ring connection. What were you thinking of as an alternative?

 

[btrueblood]

He is saying no joint at all is more reliable than any other type of joint. I think.

 

[vettedude05]

Trelleborg has an Trelleborg has an excellent O-Ring calculator. It is the BEST I have ever seen. It will recommend standard Dash Size O-Rings for your application. It will give you recommended grooves for dynamic or static applications. It tells you thermal expansion and TONS of other useful information. If use O-Rings this program is a MUST HAVE!!!

 

[vettedude05]

Inch version above... Metric version here

 

[dgallup]

Quote Flash3780

In my experience, radial o-ring connections are a very reliable method of producing a non-permanent pressurized connection. I've always felt them superior to compression fittings in dynamic applications; it is often easier to provide secondary retention to the threads in an o-ring connection. What were you thinking of as an alternative?

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I agree o-rings are good for a non-permanent connection. I was thinking more of permanent installations. I have been doing fuel devices for 25 years and everything for the last 12 years or so has been 100% laser welded. Much lower defect rates. No cut, twisted or missing o-rings. No leaks due to scratches or bad surface finish.