HERMS Coil: Minimum Bend Radius of 1/2" Stainless 0.020" wall thickness

[mliptack]

I am trying to get a herms coil quoted out at a local metal fab shop. They have the tools to make the coil in ~30 seconds and make it look damn near perfect.

I want to make sure I give them dimensions that are within the capability of the material. I am thinking I will want the ends of the tube to come off of the coil at the same side of the compression fittings (to leave the center of the coil open).

From what I read the minimum bend radius is typically 3x the diameter of the tube. Would this be for the inside of the bend (ID=1.5 & OD=2") or the outside of the bend (ID=1" & OD=1.5")?

Is this a pretty good rule of thumb in general?

I would like to keep the HE concentric in the kettle.

My kettle is about 17.75" ID. Compression fittings reduce the diameter by about 1", and if the ID of the bend cannot be less than 1.5" it looks like I am limited to a 12.75" OD HE coil (probably go with 12" OD to have a little bit of room to work with when putting the coil into the compression fittings).

At 12" OD I should get about 9-10 turns in about 5", which is about 25-30' of tube.

Looking for any help or confirmation on the thought process here.

Cheers!
Max

 

[mliptack]

Heat Exchanger Modeled in Solidworks.

However, just realized a mistake of mine.

The radius of an extruded tube is based off of the centerline of the extrude, in this case, I set the radius to 1.25, which would end up giving me an ID of 1" which would probably kink/tear the tube.

Back to the drawing board.

Oh well, the progress thus far is attached.

Cheers!

 

[mliptack]

Made the updates. Changed the coil to a dimension of 12.25.

 

[Ben58]

Normal 1/2" tube benders produce a radius of 1 1/2", but with .020 wall tubing I would keep it to 2".

 

[mliptack]

Normal 1/2" tube benders produce a radius of 1 1/2", but with .020 wall tubing I would keep it to 2".

Hi Ben - Thanks for the info!

Just so we're on the same page. When you say 2" are you referring to the centerline of the tube?

With the updates I just made, drawing attached, the Radius of the bends at the centerline is 1.75

Modeling this part in solidworks, is a PITA. Took me all morning to do, and to get it to a place where I am happy with it.

I will likely draw it up for a 2" radius too, and give both drawings to the fab company, and tell them to test it first before wasting 30' of stainless.

Thanks,
Max

View attachment Herms Coil Final - Sheet1.pdf

 

[maierhof]

To me - I think you are spending too much time on the drawings and not enough time talking to the people that do it all the time: I live on the west coast so I got a hold of StainlessBrewing about a year ago and he can pretty much do almost anything you want - and perhaps a lot cheaper than your shop. I just don't know how cheap your shop that you are using is or if they are friends and giving you a special rate.

Here is the chart from his site:
Coil Height
50ft 10" Diameter 12-1/2" Diameter 14" Diameter
1/2" 10"-11" 8"-9" 7"-8"
3/8" 7-1/2"-8-1/2" 6"-7" 5-1/2"-6-1/2"
25ft
1/2" 4-3/4"-6" 4"-5" 3-1/2"-4-1/2"
3/8" 3-1/2"-4-1/2" 3"-4" 2-1/2"-3-1/2"

My advice is to email him and ask away:
His name is Zack at stainlessbrewing.com
His email is: [email protected]

His site has lots of info - and perhaps he has one cheap already in your specs. "You never know until you ask..." - that is my motto...

Brew on

 

[mliptack]

Maierhof - Thanks for the reply. There are a few driving forces behind my approach.

1) I want to learn something from it - solidworks is new to me, so I take this as a personal growth/development opportunity.
2) Anyone on this site could buy everything they need, and some do. However, others, like myself, enjoy the DIY portion of it. I enjoy the sense of accomplishment when the concept drawing becomes tangible (I'm someone who dreams of owning a 3D printer).
3) I already have the SS Tube - so it doesn't make sense to ship it out when someone in town can do the same scope of work.
4)The company I work for does a lot of work through the shop I am going to - doesn't mean I'll get any discount, but who knows.

Cheers!

 

[maierhof]

Maierhof - Thanks for the reply. There are a few driving forces behind my approach.

1) I want to learn something from it - solidworks is new to me, so I take this as a personal growth/development opportunity.
2) Anyone on this site could buy everything they need, and some do. However, others, like myself, enjoy the DIY portion of it. I enjoy the sense of accomplishment when the concept drawing becomes tangible (I'm someone who dreams of owning a 3D printer).
3) I already have the SS Tube - so it doesn't make sense to ship it out when someone in town can do the same scope of work.
4)The company I work for does a lot of work through the shop I am going to - doesn't mean I'll get any discount, but who knows.

Cheers!

That is great to hear! Kudos to you if you are in that biz too. Hopefully they will give you a discount... My brother is an engineer and gets deals from his contractors all the time.

As far as the DIY aspect - bingo - that is exactly why I love this hobby too. My problem is that I just don't have the capabilities as a welder or have a commercial tube bender on hand. It sounds like you are one step ahead of me on the SS tube - I ended up just using his specs and bending my own copper for a CFC and my HEX at the same time... and I have been good with it for the last year. It sounds as if you are going in the right direction so there is no need to linger on this anymore - enjoy!

 

[mliptack]

As far as the DIY aspect - bingo - that is exactly why I love this hobby too. My problem is that I just don't have the capabilities as a welder or have a commercial tube bender on hand. It sounds like you are one step ahead of me on the SS tube - I ended up just using his specs and bending my own copper for a CFC and my HEX at the same time... and I have been good with it for the last year. It sounds as if you are going in the right direction so there is no need to linger on this anymore - enjoy!

Wouldn't it be nice if $10k+ tig welders and CNC tube benders were readily available to the hobbyist? I probably would have been done (or at least closer) to my end goal by now.

I will probably have extra SS tube, if you have anything in mind that you need, let me know, I will toss a quote out and see what they can do. I made up a bunch of random parts, MLT pick-up tubes, BK whirlpool out/in tubes etc.

Cheers!
Max