The Coil of Hermes

In Greek mythology, Hermes is known as the "trickster" always playing pranks on the other Greek gods,out witting them with his winged sandals and thinking the whole time how clever he is.  The HERMS coil I built for my brewery seemed to be failing on all accounts when I tried to construct it, until I outwitted fate and came up with a solution to this problem before it "spiraled" out of control.

I have a number of readers of this blog that don't know the first thing about home-brew other than how to drink it, so you home-brewers reading this have a little patience while I explain what a HERMS coil is.  There are several acronyms for some common brewing tools, most of which have to do with heat management of some kind.  HERMS stands for "Heat Exchange Recirculating Mash System", basically using an exchange coil to transfer heat from one vessel into another like a radiator but with water instead of air.   This animation from High Gravity Brewing explains it visually.  We can discuss later whether the word "recirculating" is redundantly redundant. Circulating seems to communicate the idea clearly, but it doesn't make a good acronym.  HECMS just isn't as catchy.  CHEMS? That could have a future, but HERMS has been around a while.

 3 Dog Brew RIMS Heating Element

Another design is a RIMS "Recirculating Infusion Mash System (which I have tried before) where a small amount of mash pumped through a directly heated tube.  And, there's that word again, recirculating. I used a 2 inch by 12 inch copper tube that had a water heater element at one end.  I feel the HERMS system works better and has fewer issues.  I have cooked an element more than once by letting it run dry either through a stuck mash or just forgetting it was on and draining it.

When I started the project to convert my system from RIMS to HERMS, I was following the design well documented by Kal at The Electric Brewery.  I can't recommend this enough.  Buy the man a beer, pay the $20 for his guide book.  You won't be disappointed, and it supports all the work he put into this.

I purchased the 50' coil of stainless steel tubing from Kal's site for the Hot Liquor Tank and when it arrived, I immediately set out to fit the new coil into the tank.

 Hmm.  The coil that arrived from Amazon was 50 feet long and 2 feet (that's 24 inches) in diameter.  Easy, right?  Just recoil it per Kal's instructions on this page of his guide.  It appears simple, just stand on the coil and reform it using tie-wraps to hold it in place until you fit it into the HLT.  Except I was getting this (image at right). This looked nothing like what Kal's was demonstrating in his guide.  What was I doing wrong?  My coil was "folding" not bending.

Mr. Buttons does not approve of this design.  Look at that face. Does he look like he's happy with me?    Probably because I made him sit still for a picture.  Just a small plug for Lone Star Boxer Rescue, or LSBR on Facebook where we got Mr. Buttons from.  Rescue a dog (or a cat), it'll change your life.

Mr. Buttons

After getting frustrated with this for many hours and trying to figure out why Kal was so much better at this, I realized my error.  Kal was using a 20 gallon pot as his HLT and I was using a 15 gallon.  The pots are significantly different in size.  Roughly 25% bigger, imagine that!  I had just eye-balled my desired coil diameter and came up with about 12 inches.  Kal could create a coil up to 16 inches in diameter with his 20 gallon pot and that 4 inches in diameter was putting a "crimp" in my project.  He never mentions in his instructions the desired coil diameter for the HERMS coil, I'm just guesstimating.

Motorized grain mill

I put my toys away and decided that I needed to noodle on this for a solution that a) would give me what I needed and b) didn't require me to spend more on tooling than I spent on buying the raw tubing.  I was trying to think large scale.  What would a big machine shop use to recoil a coil of tubing or stiff wire?  They would use some sort of compression wheel with an offset guide to keep the coil from springing back to it's previous shape.  After scrounging through the garage/brewery for a while, I realized that I already had the perfect tool, in the correct diameter and that all I needed to do was find a way to secure it and to build some forms to keep the tubing coiled around it. It's called a sheave, but you probably think of it as a pulley.  I had a 12 inch sheave on my
grain mill.  There's a large coil of 10 gauge, 4-wire cable sitting on top of the grain mill that was used later to send 240 Volts at 30 Amps to the main control panel.  I can't decide if I hear Gru from Despicable Me or Tim Taylor from Home Improvement saying that.

So, remove the sheave from the grain mill, mount it to a flat table with room for the coil on either side and find a way to hold the tubing tight against the sheave as I wind it around reducing the bend radius.

I bolted the sheave to a large square piece of 3/4 MDF I had sitting around but plywood would have worked just as well. Then made a fence by gluing some MDF together and bolting that to the large square piece.  I bolted a "handle" made of another longer piece of the same MDF and used a U-Bolt to loosely attach it to one of the spokes of the sheave to make turning the whole contraption a little easier.  As you can see in this photo the system worked and I soon had a coil that went from 24" in diameter to 12".  I used clamps to hold the tubing in place as it worked it's way around the sheave.

 It wasn't "easy" and you can see in one of these photos that the "handle" I made failed and broke where the U-Bolt was.  Just keep turning the wheel and it continues to work.

Now that I had a nice HERMS coil, I had to bend the ends even sharper to exit the pot at right angles.  That's where the giant tubing bender comes in (red handles).  After all that work the last thing I wanted to do was to mess this up and have to start all over.  I used some of the pieces of destroyed tubing shown earlier to test bending the tubing to meet the sides of the pot.  This was more difficult than I imagined and I crimped several pieces of tubing and had to cut them off to start over.  Doing some quick math on what I had that was still good, 12 coils at 12 inch diameter, I had taken a 50 foot coil of stainless tubing and turned it into a 35 foot HERMS coil.

Yep. I ruined 15 feet of tubing trying to figure this out.  Someone else figured out that by using 90 degree compression fittings, you don't have to make those crazy sharp bends in the tubing.  Wish I had thought of that. Would have saved me a ton of grief.  So there you have it, another adventure in home brewing and how I managed to outwit Hermes and create my own HERMS coil.