Coiling 316L Tubing?

[MeuserReef]

Im building a new, inline heat exchanger for my DIY chiller. I have purchased a 6' length of .50" OD 316L stainless steel tubing (.028" wall thickness). I would like to coil this tube into as tight of a coil as possible. Whats the best way to coil this stuff? Pipe bender? Custom made roller?

I have never bent this stuff before and could use some help.


ps.. I know that Ti is the preferred material to use for this (I have Ti in my current heat exchanger) but I have weighed the Pro's and Con's and feel comfortable using it in my setup.

 

[PrivateJoker64]

I'd use either a spring type bender (harder to use, but cheaper)

or a lever style bender (harder to make continuous coils)

If you just try to hand bend it, you will likely collapse it.

 

[JCTewks]

you might be able to fill the tube with sand and put duct tape on both ends before you bend it to keep it from collapsing. I've seen people do that with PVC when bending it and it seems to work well to keep the PVC from deforming during the bending. THe sand would serve a similiar purpuse as the tube bender in the first pic.

My guess is that heating it would make it easier to bend...although you'll still want some sort of precaution to keep it from kinking.

 

[MeuserReef]

Thanks for the info! PrivateJoker64, How does the spring type bender work? Ive seen the other type of bender pictured above in action and I can see how it would not produce a clean, consistant coil. I have heard about a "roller" that a guy used to coil Titanium tubing, but have been thusfar unable to get anymore details on how the roller was made.

JCTewks, I had considered the sand as I have seen the PVC bending process before, but wasnt sure if it would work on SS. Anything to prevent collapsing the tube is worth it to me. I will certainly add this to my to-do list. I would have to believe that SS would have to be heated pretty hot to be able to bend freely. I would like to try to keep any parts of the tube from becoming stretched too thin as this will likely lead to premature failure, which would equate to dosing my tank water with R-22 (not so good)

Thanks for taking the time to offer help.

 

[JCTewks]

roller benders are pretty straight forward....

The rollers start out in this position...
<a href="http://s120.photobucket.com/albums/o186/JCTewks/?action=view&current=Steelroller.jpg" target="_blank"><img src="http://i120.photobucket.com/albums/o186/JCTewks/Steelroller.jpg" border="0" alt="Photobucket"></a>

And you get the top roller closer and closer to the bottom 2 until you end up with this...
<a href="http://s120.photobucket.com/albums/o186/JCTewks/?action=view&current=Steelroller2.jpg" target="_blank"><img src="http://i120.photobucket.com/albums/o186/JCTewks/Steelroller2.jpg" border="0" alt="Photobucket"></a>

At which point you have a full circle

Sorry for the crappy paint drawings...it's late and I wanted to respond before I forgot

 

[JCTewks]

The spring type bender....

You just insert the spring into the tubing and bend by hand....the spring simply keeps the tubing from kinking!

 

[MeuserReef]

Thanks alot Jeff. As you can see, I wasnt lying when I said I needed help!

The paint drawings do a perfect job explaining your point. Im curious how one would build a roller?

So the spring type bender and the sand are pretty much one in the same with respect to function,

 

[MeuserReef]

Double post

 

[MeuserReef]

Triple Post! Whoa... never done that before!

 

[JCTewks]

Yes, sand and the spring serve the same function.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=36698 here's a link to one that yo can purchase...however, this model has wire forming grooves only up to 3/8" and you need 1/2". Check around with local metal fabrication shops and see if any of them can roll 1/2" tube. A friend of mine locally has a sheet metal shop, he has rollers with wire forming grooves up to 3/4" on 1 of his rollers.

 

[MeuserReef]

How hard would you imagine it would be to fill the tube with sand and bend it by hand? The thin wall should help.

Im just hoping that Im not going to have to spend any more $$$ to get this thing created.

I appreciate the link too.

 

[JCTewks]

I wouldn't think it would be that difficult as long as you used something to roll it around...I would think a piece of PVC would work as a former. You could use duct tape to hold one end to the PVC and just wrap it around the pipe.

 

[vvolfe1]

How tight of a bend are you looking for? It is pretty easy just attaching tubing to a piece of pvc with a U-bolt. Then you just need to rotate the pvc on a bench and keep it straight.

 

[MeuserReef]

vvolfe1, thanks for the input. I was thinking of using PVC ad a form but hadnt figured out how to hold the tubing to the pipe. I was thinking tape, but then I also figured that it would pull free from the PVC once tension was applied to it. The U bolt is a good idea.

Im hoping to be able to create a coil < 3" in diameter (closer to 2" if possible).

The housing that this will go inside of is going to be made from 3" PVC pipe, so it will need to be smaller than 3".

Do you think that a 2" - 3" diameter coil is realistic if bending around a piece of PVC pipe (2" pipe used as a form perhaps?) I would fill the tube with sand to prevent caving the walls in and creasing the tube.

 

[BeanAnimal]

If the former pipe is around 2" O.D and the tube is around .5" O.D. then you are going to end up with a coil that is in the 4" - 4.5" O.D. neighborhood.

 

[MeuserReef]

Thanks BeanAnimal! Do you think a smaller coil is possible, one that would allow me to fit the coil into a 3" piece of PVC ?

 

[BeanAnimal]

I dunno... I suppose it is possible, but will depend a lot on the technique you use. By hand? I dunno... if you had a set of rollers, I am pretty sure you could.

 

[JCTewks]

Are you dead set on using 3" pvc for the chiller barrell? I would think that a coil that small would be difficult to make without LOTS of tiny stress fractures in the SS....at least doing it by hand would cause them.

Maybe you could upsize your barrell to 6"....or just see what size coil you end up with and size your chiller barrell from that!

 

[MeuserReef]

JCTewks,

Im glad you mentioned the risk of stress fractures, especially when bending by hand.

Im actually starting to think that the risks involved with coiling the material arent worth it, and would possibly leave me with a less stable system, long-term.

Is there really a point to a coil, other than its space conservation?

I could do somethin like this and only have one bend (or 2 consecutive 90 degree bends)

The contact surface area of the SS is still the same, regardless of how its bent, correct?

 

[BeanAnimal]

Yup, and you could slide a few makeshift baffles over the lines if you want to make sure that the liquid gets good surface contact, but that really is not needed either.