Help with Sizing - Oetiker (Ear Clamps) with Eva Barrier Tubing

[Nagorg]

I need some help before I throw in the towel and go back to worm clamps.
First, I cant find any consistent sizing info for the clamps. No site I find has positive info to help find what to order. Bobby's site looks the most promising but still doesnt seem to match other sites or available sizes. Not sure why these things need to be so hard. :|

I'm using EVA Barrier tubing (2 different sizes) with 1/4" MFL swivel nuts.

Tubing Sizes:
Beer Line - 4mm ID x 8mm OD
Gas Line - 6.3mm ID x 9.5mm OD

Again, the sizing of the clamps seems inconsistent. I'm okay with dealing in metrics but I have no idea what clamps to chose for a given tubing diameter, especially when that changes after being forced over a barb.
Some sites list the clamps as a min-max size, others list a single number for the size but I've not found anything really consistent from site to site about this.

Any help available for this problem?

​

 

[McMullan]

The clamps come in a number that covers a range of diameters. There should be a sizing chart somewhere. By the time you’ve pushed on to a suitably sized barb, it’s going to be a bit bigger than the OD of the tubing. I go for the size next up from the one I think I need. I can find out which numbers are on mine later, if no one else chimes in with the info. But, yeah, it can be a PITA trial and error otherwise.

 

[Nagorg]

The clamps I used that seem perfect for the gas line (6.3mm ID x 9.5..OD) have "109" stamped on the side.

I thought this might translate to 10.9 mm. These clamps came out of an assortment box I bought from Amazon and I think the box lists these as a size "9.2 - 10.9mm" though that's not even definitive.

But when I lookup Oetiker 109 online trying to confirm, I don't think 109 really translates to the size.

https://www.oetiker.com/en-us/products/clamps-and-rings/ear-clamps/pg-109_159_163
Kegoutlet.com has a decent list of sizes with ranges but none match what I bought. There's a "close" size range of 8.8mm - 10.5mm and maybe that's good enough. I'm just getting tired of buying clamps that wind up not fitting. And buying assortments so I can try them all is giving me a nice collection of clamps I have no use for. lol

https://www.kegoutlet.com/oetiker-clamps.html
But none of this matches what Bobby has listed on his site. The clamps are all listed as max OD there with 11.6mm being the smallest; but thats still bigger than the max of 10.9mm that seemed to work for me.

Man it seems like it should be easier than this...

 

[sibelman]

I've found that, if the Oetiker is almost snug on the fitting-plus-tubing (before clamping), it's the right size.

That only helps if you have the right size on hand of course.

 

[VikeMan]

The clamps I used that seem perfect for the gas line (6.3mm ID x 9.5..OD) have "109" stamped on the side.

I thought this might translate to 10.9 mm.

That's correct. "109" means 10.9 mm nominal diameter, i.e. the clamp's untightened inner diameter. Which theoretically is a hair bigger than the maximum hose OD (or hose/barb bump OD) you could fit it over. In practice, it's better to go a little larger.

 

[oakbarn]

Get a cheap ($19) micrometer.
https://www.harborfreight.com/paint...sae-and-metric-fractional-readings-63731.htmlmeasure your tubing.
The measurement "9.2 - 10.9mm" means that it will work on anything between those two extremes.

This is perfect for you
Gas Line - 6.3mm ID x 9.5mm OD as it in the range.


You need a clamp with a range with 8mm for the beer line. If you want Oetiker clamps, an assortment is likely the best buy as getting 10 of one size is not easy to find, Packs of 50 are $$ ;


I have found that it is best to buy Oetiker brand

 

[Deadalus]

Is there a reason why you aren't using push to connnect (ptc) fittings with the tubing?

The walls of your 4X8mm tubing are 2mm. They will potentially stretch some but you could add 2 x2mm=4mm to the barb size you are jamming into them to get the maximum size the barb + tubing diameter might be. One thing I am not so sure of myself is whether a specific barb size is nominal for the inner tubing diameter it is meant to fit. A digital caliper is a really handy tool to have and not that costly.

 

[Nagorg]

Is there a reason why you aren't using push to connnect (ptc) fittings with the tubing?

Yes, I don't trust them. This is probably unwarranted since I've never used them. But I've read and heard of leaky connections. Probably not the connector's fault but clamps have never failed me. (knock on wood)

 

[Deadalus]

Yes, I don't trust them. This is probably unwarranted since I've never used them. But I've read and heard of leaky connections. Probably not the connector's fault but clamps have never failed me. (knock on wood)

I think a lot of the issue with the ptc is likely operator error, although I have had 2 fittings fail. One could have been operator error with Starsan exposure. It's hard sometimes to know definitively whether the other was operator error. They are plastic and they will add up if converting. I do have a leak somewhere in my four tap system that I haven't traced down as I also have repeated issues with my keezer lid struts. A lot of tight spaces make it hard to work on too. Not necessarily trying to sell you on the ptc fittings though.

I just bought 20 Oteiker clamps from BobbyM. I thought the info he had there was well laid out and I would trust him that for what he is selling that he actually took the time to check them out properly. Like you, I have an assorted bag of clamps but I went through the sizes I needed. The size he had listed matched up with the size I had low inventory of and had been using on my 1/2" ID tubing. As far as assortments, the same thing happened with worm clamps, I ran out of the sizes I was using most and have a plastic box full of sizes I don't use!

 

[mac_1103]

I have 10.5 mm clamps on 4 mm tubing swaged over 1/4" barbs.

 

[oakbarn]

I have 10.5 mm clamps on 4 mm tubing swaged over 1/4" barbs.

It is important to measure the tubing "ON" the barb. I forgot that little fact and have a bunch of clamps that are too small. You want the clamp to slide over the tubing while installed on the barb. I find that putting the tubing in hot water makes them much easier to put on.

 

[Broken Crow]

I know 95% duotight users have no problem, but I've had 3 leaks with them, at least one of which was defective part...the other 2 may have been user error because I don't have the physical or cognitive capacity I used to. I don't trust them in the long run either. If it's not too late, do yourself a favour and get the 3mm ID EVABarrier..it's great to have such short lines! Approx. 37", using 9.5mm oetikers.
I tried to detail it here:
https://www.homebrewtalk.com/thread...mm-monotight-connector-duotight-shank.730515/I'll be doing my gas lines next and switching out to the 1/4"ID EVABarrier shoved over 5/16" swivel nut nut barbs, but I haven't figured out which oetikers to use yet...I've got a couple assorted packs of them and I'll just try them out, but I'll be keeping an eye on this thread.

 

[McMullan]

On my 9.5mm OD EB tubing with 1/4” barb clip is ‘12.8’.

On the 8mm OD with 1/4” barb it’s ‘10.5’.

I prefer to fit the Evabarrier tubing like this for things that get moved around a lot, like my mobile gas line or lines I undo for multiple applications. You can’t beat a swivel nut on the end of a line. The duotight fitting seem fine when thing are setup to be fixed. Like all push-fit fittings, they’re not designed to be repeatedly disassembled.

 

[sibelman]

1/8” barb

Great post and pics. I think you meant 1/4“, no?

 

[McMullan]

Great post and pics. I think you meant 1/4“, no?

Yes, 1/4”. Good call.

 

[Deadalus]

The caliper I have reads fractional inches, decimal inches, and decimal millimeters. I didn't bother with decimal inches. I went and measured four 1/4" swivel nut barbs that I had. They were all reading 9/32" as the diameter of the high ridges and about 7.2mm for metric. The barb is 75% larger than 4mm ID. Obviously the tubing is getting stretched to put it on the barb and quite a bit. Using the 2mm wall thickness, without stretching, you'd need something 11.2mm or greater. I suppose you could calculate the ring area of the stock tubing and then use that area to solve the area for a ring with the inside radius being 7.2mm/2 to get an idea as to how thick the walls are after insertion. I would guess that perhaps the barbs press into the tubing walls some.

Solving that for the 4x8mm.

tube cross sectional area=pi(8/2)^2-pi(4/2)^2=12pi.
pi(new outer radius)^2-pi(7.2/2)^2=12pi
new radius squared-3.6^2=12 [Divide out pi]
new radius squared=12.96+12=24.96~25mm

So the new outer radius is just about 5mm and thus the diameter is 10mm. If you subtract out the barb diameter, that's 2.8mm. Divide that by 2 and the new wall thickness is 1.4 mm. That's 30% smaller than the original 2mm. I suppose a matched size barb would still stretch the tubing a little as here the 1/4" barb is slightly larger on the ridge but probably not as much with the correct size.

 

[mac_1103]

I suppose you could calculate the ring area of the stock tubing and then use that area to solve the area for a ring with the inside radius being 7.2mm/2 to get an idea as to how thick the walls are after insertion.

Or maybe you could put the tubing onto the barb and THEN pull out your calipers.

 

[Deadalus]

Or maybe you could put the tubing onto the barb and THEN pull out your calipers.

Not everyone has calipers so explaining a method to figure it out can be informative. I also don't have any 4mmx8mm Evabarrier, much like you must not have access to calipers. I'm also not a fan of using oversized barbs in general. If the tubing is designed to accept a barb and uses inner diameter as its size class, matching the correct sized barb to the inner diameter is really how the manufacturers generally expect the two to go together. Having done the calculation, it shows how much the material is being stretched. Potentially not a problem, they make 5mmx8mm, which is what I use, and the wall thickness there is 1.5mm. But since it's proprietary, it's not clear where the double wall transitions and whether stretching it that much affects its properties.

 

[mac_1103]

Not everyone has calipers so explaining a method to figure it out can be informative.

At first I wrote "put the tubing onto the barb and try to slip clamps over the connection until you find the right size" but that only works if you already have a bunch of different sized clamps. But anyway you can just use a ruler. It's not like this requires extreme precision since the clamps are designed to work on a range of diameters.

If the tubing is designed to accept a barb and uses inner diameter as its size class, matching the correct sized barb to the inner diameter is really how the manufacturers generally expect the two to go together.

Where does one get 4 mm barb? And what good does that do if you're trying to attach EVA barrier tubing onto swivel nuts or barbed shanks that you already have?

 

[Deadalus]

At first I wrote "put the tubing onto the barb and try to slip clamps over the connection until you find the right size" but that only works if you already have a bunch of different sized clamps. But anyway you can just use a ruler. It's not like this requires extreme precision since the clamps are designed to work on a range of diameters.

Where does one get 4 mm barb? And what good does that do if you're trying to attach EVA barrier tubing onto swivel nuts or barbed shanks that you already have?

I think you want to argue for some reason because I used a caliper. One could also use a ruler if that's what you have and your eyesight is good. A caliper is a pretty cheap tool to have as I said and pretty handy when dealing with tubing and pipes. It's not really a wide range of diameters the clamps work on either, it's just 1-2 millimeters. It might spare the wait involved with a second shipment if you are off on something that falls on the edge of the clamps range and you pick wrong. Saving the shipping cost may just pay for the tool. And that applies to each time you use the caliper, it could be for a variety of projects. Saving a trip to the hardware store here or there will also pretty much pay for itself honestly.

Evabarrier is designed to be used with ptc fittings. But here's a 5/32 barb for use with a 1/4" swivel nut. It says (3/16") in parentheses which I am guessing is the actual and the 5/32" is the nominal, with 5/32"=3.969mm. Just because all you've got is the wrong sized fitting doesn't mean you should use it. Now I don't know what size the ID of the barb is, and that's a problem with barbed fittings as they constrict the flow. So I get why people upsize the barbs at times. However it may come with a cost of potentially impacting the function of the tubing in some other way as the tubing is stretched, A recommendation to use the right size fitting for the connection is a perfectly normal suggestion as that's how the system is designed.

 

[mac_1103]

I think you want to argue for some reason because I used a caliper.

Actually I don't want to argue at all. Just thought it was worth pointing out that you seriously over-complicated the question IMO.

 

[Deadalus]

Actually I don't want to argue at all. Just thought it was worth pointing out that you seriously over-complicated the question IMO.

I can understand you might consider opening a caliper and reading decimals and fractions to be tough but honestly it's pretty simple. And faster than eyeballing a ruler anyway.

And the OP was interested in solving this:

Again, the sizing of the clamps seems inconsistent. I'm okay with dealing in metrics but I have no idea what clamps to chose for a given tubing diameter, especially when that changes after being forced over a barb.

The example I provided allows for an estimate for the clamp size needed and illustrates how the size of the barb is affecting the overall combined diameter while noting potential unforseen consequences. It used a calculation for ring area and a little algebra. Sorry if you think that's complicated, I did use numbers not variables. It provides an example and a method to determine what was asked by the OP. Your answer didn't even consider that there are different sized barbs to begin with for older style lines so save the criticism.