O-Rings for a compression fitting - Home Brew Forums
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Old 06-06-2010, 05:22 PM   #1
jtrainer
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I'm building a new boiler and as such a new dip tube. I have several DT's but the nuts never come off and over a couple years there is a build up of crap at the joint.... I'm willing to try the o-ring solution here...

I picked up 5/8 ID high temp o-rings at True Value. They said they were Buna-N for the material, I also picked up an HNBR o-ring but just read HNBR is another name for Buna-N or so I read someplace.

My initial tests show it appears to be sealed and sealed well. I have not installed the solution yet. But the finger tightening seems to work great.

OK So what size o-rings are being supplied for a compression fitting of say 5/8 (copper dip tube) is 5/8 O.D.?


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Old 06-07-2010, 12:16 AM   #2
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HNBR and Buna-N are not the same rubber. HNBR is "hydrogenated NBR", NBR is another name for Buna-N. If they are food grade, either will work, HNBR is better at high temp in harsh chemical environments. Brewing is not a harsh chemical environment, at least it shouldn't be.

Using an O-ring in the compression fitting will work nicely, the size you want for a 5/8" dip tube is 5/8 ID, and probably 1/16" thick, so 3/4" OD, since it needs to fit into the annular space between the tube and the compression nut.



 
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Old 06-07-2010, 01:16 AM   #3
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Got it... I'll hold out for some silicone ring then...just to be sure...
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Old 06-07-2010, 01:39 AM   #4
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When you ask which oring size is supplied... I don't get it. I don't know of anyone selling compression fittings with orings. It's a homebrewers construct.

#112 or 113 will work great on 5/8" OD tubing. You'll want to stack 2 or 3 in there.
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Old 06-07-2010, 01:47 AM   #5
jtrainer
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Nope nothing supplied other than the brass ferrule. I'll look for the silicon 5/8 ID o-rings..

thanks
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Old 06-07-2010, 06:23 PM   #6
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FYI: Buna-N is fine to use as long as it's not in a dry heat area.

Buna-N is rated for temps above boling and, depending on the brand, will be either ANSI rated for use in potable water systems or full-blown NSF rated. (The difference is simply whether or not the manufacturer coughed up the money for NSF certification... the material is the same in either case.)
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Old 06-07-2010, 06:59 PM   #7
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I'm not so sure all Buna-N O-rings are potable water or food safe. A heck of a lot of Buna-N is used in automotive fuel and oil handling systems, and I doubt these compounds are food safe. There is no point for the rubber molder to use a food safe formulation for gas line orings or oil seals. There are for sure food grade O-rings available, but I wouldn't count on finding them in the bin at the hardware store. These probably come from a distributor who buys the cheapest ones available, and doesn't specify food grade. That being said, I would not use the hardware store variety for my brewing applications, I'd find food or potable water safe ones, maybe from McMaster Carr, or Grainger. Or go with food grade silicone if I wanted to spend a little more.

 
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Old 06-07-2010, 07:02 PM   #8
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Yeah, you're probably right that not all are food safe.

If you shop at Lowe's, the o-rings they sell for faucet repairs are from a company called Danco, and I actually called them up and spoke with them to get the info about their particular o-rings to get the details. The Danco ones are a-ok to use.
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Old 06-07-2010, 07:07 PM   #9
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Yor're absolutely right, faucet repair O-rings are (I hope!) potable water safe, and would be fine for brewing. I wasn't thinking about plumbing stuff, but the anonymous O-rings in the little draws at good hardware stores.

 
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Old 06-07-2010, 10:19 PM   #10
jtrainer
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Walker, that's most excellent info.. I'll be headed to Lowes for the faucet O-Rings from Danco..


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