Stainless steel conical beer fermenter Pt.8

The beer fermenter project is finally ready for its first batch of beer. I bought a soft silicone strip from McMaster and cut a scarf joint in it. The diameter of the finished ring matches the lid on the fermenter.






I did some testing and verified that standard silicone adhesive would bond the red silicone rubber strip very well. I am pretty sure that if tested to destruction, the glue joint would break before the rubber itself would, but it still seems tough enough for this application.

I also welded my stainless cooling coil into the lid.


I made some Delrin clamps to keep the lid held tightly onto the tank. The silicone rubber is very soft which helps easily make a seal with minimal clamping pressure. I clamped it all up, shut both valves, and sucked some air out with my lungs. I could feel the vessel holding the vacuum that I created, so I assume the setup is essentially air-tight.

OK, so now it's time to brew some beer! Any recipe suggestions?

Stainless steel conical beer fermenter Pt.7

The conical fermenter project is coming along well. Here is what's left to do:
1. Mount stainless cooling coil (chiller) to bottom of lid so that I can quickly chill the hot wort after boiling.

2. Make a silicone seal for the lid

3. Make some beer! Wow, I can't believe this project is almost done... it's taken a long time.



Here's a picture of the lid with a thermowell that I made. The thermowell allows a temperature probe to be inserted deep into the tank without exposing the tank to the outside air. It's basically just a long stainless tube that is welded to the underside of the lid and sealed (welded) on the end.

The peltier heating/cooling module is working pretty well despite the copper block soldering mishap. The thermal conductivity is not nearly as good as it should be, but it still seems to work well enough. My original plan was to use two separate peltier modules, but so far, one seems to be sufficient. Without any insulation on the tank, the device held a 15*F difference from ambient temperature, so this project may not even need much insulation.

The temperature setpoint is 67*F. For actual beer brewing, I'm thinking 64*F will be the target ale brewing temperature. So far, I am just using proportional control with a very high proportional constant. The tank has so much volume, and the heating/cooling power of the peltier is relatively tiny, so there isn't much tendency to oscillate.

Stainless steel conical beer fermenter Pt.6

I decided to scrap the idea of using my ring burner shown in "part 5" of my conical fermenter series of posts. Instead, I started reading about home-built propane burners for use in small metal-working forges.

These sites were very helpful:
http://www.zoellerforge.com/sidearm.html
http://ronreil.abana.org/design1.shtml
http://www.backyardmetalcasting.com/oliverburner1.html

I decided to follow Mr.Zoeller's design, for which he was kind enough to post a PDF and provide great instructions.




I used an 1/8" NPT brass cap to seal the end of the 1/8" pipe nipple instead of a Tweco Mig tip. I drilled a .035" hole in the center of the brass cap after machining the sides and face smooth.


I used a 3/4" to 3/4" extender as a flare. I cut out the threads on the lathe, leaving a 1:12 taper on the interior surface. I tested the burner briefly before cutting the taper, and I'm not sure how much it really helped. I never tested it without the flare.


This is really a very good design. It can be built from parts found at any hardware store, and it only requires a couple holes to be drilled. The performance seems to be quite good. I do not have any other burners to compare it to, but I am quite pleased. It doesn't like to run at very low pressures. The flame will be drawn back into the tube, and it starts to sputter (as well as heat up the tube). Above 3 or 4 psi, it runs like a champ, and the adjustable air shutter is a critical piece. Without the air shutter, the flame is very lean and might blow itself out. I kept the shutter half-closed, and this seemed to produce a very neutral flame.

I fitted the conical with its valves and added 1 gallon of tap water. The burner is mounted by simply placing it between two short stainless pipes that I welded onto the frame rail. There is currently nothing holding the burner in place except gravity. I'll probably add a pin or strap to prevent the burner from accidentally falling.

Cool!


I achieved a full rolling boil in 20 minutes (1 gallon of water). I started out fairly low with the gas pressure, and gradually increased it, as I saw nothing bad happening.

Stainless steel conical beer fermenter Pt.5

I found a 0-10 psi adjustable propane regulator at Home Depot. It was a closeout item with a price of $4.99! I built a circular burner from 5/8" copper tubing and soldered in some "jet burners" from the ubiquitous 23-jet wok burner.


The 23-jet burner is available in natural gas and propane versions. I ordered the propane version from kitchensupplydirect.com (it was on sale for $20.03 a few weeks ago), but they might have sent me the natural gas version. I suspec this might be the case because the burner runs very rich. Take a look:


The yellow tips on the flames show that there is a lot of excess fuel. The flames are jumping off the burners probably because the mixture is too rich to start combustion inside the burner tube.

I ordered some hypodermic tubing from McMaster and made the jets smaller by press-fitting the hypodermic tubing into the existing jets. This changed the jet size from about .023" to .012". Now, the jets seem to burn too lean, and have a very hard time staying lit. The slightest breeze blows the flame out. When the burner was running too rich, it also could be blown out by slight breezes. I think the burners are not designed very well. The original orientation in the 23-jet burner caused a lot of turbulence to be generated -- it positioned the jets to aim into each other's path. This might have been a required design element to prevent the flames from being blown out.

Anyway, I'm considering a different propane burner design. More later.

Stainless steel conical beer fermenter Pt.4

Today I built a three-legged support structure to hold the beer fermenter. My original design called for welding three square cross-section tubes to the sides of the conical tank. I decided against this method because I wanted to ability to remove the tank from the stand, and I was also a little worried about having inadequate argon coverage on the weld backside (in the tank).



The three legs are only held together by the welds near the ground. The tank just rests on top of the legs. I may add some strapping to prevent the legs from splaying outward from the conical tank, but so far, this doesn't seem to be much of a problem. The legs are all 304 stainless steel - same as the tank.


I was surprised how little filler rod I needed for these welds. Next time, I will make my tack welds much smaller, because the weld bead itself was very tight, and the globs of filler from the tack welds were annoyingly large.


I welded some stainless nuts to small sheet metal structures, then welded the assemblies to either side of the copper heat block. The two nuts will allow me to sandwhich the Peltier between a large heatsink and the copper block. I'll use nylon screws to prevent heat transfer and also to make the compression on the Peltier more gentle and balanced.

Stainless steel conical beer fermenter Pt.3

I just finished welding together the stainles racking cane for the beer fermenter project.

Even though this may not look like much, I am quite proud. It is a 5/8" dia stainless tube, but the wall thickness is only .020". I sliced it on my new metal band saw, reoriented the pieces to make an elbow, then tacked it in two places, and welded all the way around. It's air-tight. The trick is to get the tacks done really quickly. I only used filler (.035") to make the tacks, then just fusion welded it in very short sections (a few seconds at a time). I blew through it once, and had to repair it with filler.

Here's the tube welded to a tri-clamp plate, which is welded to one side of a three-piece ball valve.

Here's the other side of the ball valve welded to a hose barb.

The complete assembly is attached to the tri-clamp port on the side of the tank. The purpose of all this hardware is to be able to rotate the racking cane while draining beer from the tank. Thus, the height at which the beer is drawn can be adjusted. This allows the maximum amount of clear beer to be drawn from the tank without getting any cloudy beer that has settled to the bottom.

Inside the tank.

Stainless steel conical beer fermenter Pt.2

The next step in the beer fermenter project is to mount some copper blocks to the outside of the stainless tank. The purpose of these blocks will be to thermally couple two peltier devices to the surface of the tank. The tank is cylindrical (near the top) and the peltiers are flat, so the copper blocks must be curved on one face, and flat on the other. I started by cutting off some chunks of copper and milling the edges square.



Next, I used a long end mill to profile the sides with a radius that matches the outside of the stainless tank. My plan was to silver solder the copper blocks to the stainless tank exterior. This turned out to be a very bad idea. I started by fluxing the copper and stainless, then separately covering them with a thin layer of silver solder. No problem yet. I put the semi-cooled block onto the tank, and planned to heat the tank and block and let the two solder-covered surfaces melt together. This started working, but then the stainless expanded dramatically under the block. The copper was lifted a clear 1/4" off the surface near the edges, while the center was making contact. I removed the heat, and looked inside the tank to find this new disaster:

A monster crack had developed in the wall of the tank! I am still not sure why this happened. It obviously has something to do with the metals' differing rates of expansion, but I had no idea the consequences could be so damaging. Perhaps this has something to do with the stresses in the metal from the spinning (cone-forming) operation?

Luckily it wasn't too difficult to repair the crack. Since the crack went clear through the tank wall, I had to fight the silver solder which was molten and trying to flow into the weld puddle. The copper blocks must be making good thermal contact, since I maxed my TIG machine out at 200A, and it was just enough to comfortably weld.

There are two copper blocks (each made of two pieces of bar). In order to avoid the silver-soldering nightmare again, I used silver epoxy to join the copper to the tank. After both blocks were attached, I mounted the assembly in the milling machine, and flattened the faces.

If I were going to do this again, I would profile the copper backside, flatten the face, then use silver epoxy to attach it to the tank.

UPDATE: This method did NOT work. I was not able to hold the glass without rocking it very slightly. This created a very smooth, but curved surface on the copper. It was unsuitable to mount the peltier.

Here, I am removing the milling marks with sandpaper mounted on a 1/4" thick glass plate. This took a very long time. In fact, I am still "going up through the grits" right now. The next step will be to weld a small threaded boss on either side of the copper blocks. This will serve as an attachment point for the peltier heatsink. The peltier itself will be pinched between the copper and the heatsink.

DIY stainless steel conical beer fermenter Pt.1

Please search my blog for "fermenter" to find all of the posts regarding this project.

I am building a stainless steel tank that will eventually become a very unique beer-brewing vessel. My idea is to make a tank such that the entire process can take place without ever having to transfer the beer from one tank to another. This vessel will boil the wort, chill the wort, provide a temperature-controlled fermentation period, allow the trub to be removed, and provide a secondary fermentation. This tank was designed with my experience in brewing about 30 5-gallon batches of beer using the extract process. I don't have much inspiration to do all-grain brewing yet.

Having said all of that, I am also learning to TIG weld, and this project will provide many different welding setups -- all in stainless steel.


I bought a stainless steel conical hopper, model TMS14514 from
http://www.toledometalspinning.com/products/hoppers/priceList.asp

Toledo Metal Spinning sent the item very quickly, and I am impressed with the quality. The edges are extremely flat, and the overall finish and dimensional tolerances are great.

It holds 6.4 gallons total, so a 5 gallon batch of beer should fit pretty well. The hopper is a continuous piece with no hole in the bottom. I will be mounting a butterfly valve at the apex, so I need to cut the tip off to match the diameter of the valve housing. I knew before I ordered the hopper that I would only need to slice off about 1/8" off the end.

I used a slitting saw in my milling machine to do the job. This left me with a super flat clean edge. 70 RPM, 0.5 inches per minute, however the feed rate is measured at center of the saw, and I programmed a G2 circular path. This means the feed at the cutting point is probably lower. I had problems with chatter, thus necessitating this low feed rate.

This is one half of the butterfly valve housing after I welded it to the cone. The blue hose is silicone, and is carrying argon to the backside of the weld. In addition to the foil on top, I have made a dam with aluminum foil and tape inside the neck of the cone to trap the argon in the space around the weld.

Since the first weld went so well, I decided to weld on the inside of the fitting as well. Ultimately, this was not a great idea, but the weld itself went well. I used a copper tube with a line of tiny holes drilled in it to disperse backing argon to the outside of the cone. I had a fair bit of room inside the valve fitting for the TIG torch and filler rod.

I used a die grinder to smooth out the interior weld. After putting it together, it leaked! I had used the die grinder too much, and made the metal thin enough where a tiny pinhole in the weld made it all the way through the metal. I re-welded the outside bead, and then realized that I should have just made a couple of passes on the exterior to build up material. Then I could die-grind away the inside until I ground into the weld bead. No need to weld the interior. This would provide a nice smooth surface inside the tank and ensure there was enough material to keep it structurally sound.


It looks good now.


I originally started to cut this hole with a high-quality hole-saw in a corded drill. After a few seconds, I realized it was probably not going to work. Stainless is just such a tough metal, cutting tools just bounce off it. I used a free-hand plasma cutter to make the hole.

I made another aluminum foil/tape dam around the wall on the interior.


The weld went pretty well.



This time, I learned how to do it. Instead of welding on the inside, I just built up a nice bead, then used the die-grinder on the interior until I ground into the bead. It's nice and smooth on the inside.

Peltier power supply and integrated PID controller

I am preparing to build a beer-brewing tank that will be temperature controlled. The goal is to keep the vessel at a very steady 72*F. Depending on the time of year, this might require heating and/or cooling 24 hours per day, or heating during the night and cooling during the day. Since the only heat load on the vessel is the heat leakage through its insulation, the total amount of heat that needs to be pumped is fairly low. This might be a good application for a Peltier heat pump since the heat load is low and the heat pump direction might need to be changed often.

As I mentioned in my aquarium chiller post, the Peltier module must not be controlled by PWM (pulse width modulation) or on/off thermostatic control. During the 'off' part of the cycle, heat will flow backward through the Peltier device and decrease efficiency almost to zero. Ideally, the PWM output should be smoothed with an L-C (inductor-capacitor) circuit to provide clean DC power to the device.

I happened to disassemble a thermoelectric refrigerator (and replaced its guts with a refrigerant-based system in a previous post) and had a 115VAC Peltier power supply and Peltier module. The power supply uses a TL494 IC to control a 115V->12V high-frequency transformer. The output of the transformer is smoothed with an L-C circuit. The TL494 is controlled by the output of a thermistor and digital thermostat, thus sending more power into the transformer when the fridge's temperature exceeds the thermostat set-point, and reducing power when the temperature falls below the set-point. I couldn't figure out the analog side of the circuit which had a few op-amps. Instead, I discovered that I could throttle the power supply by putting voltage on the TL494's DTC (dead-time control) pin, which wasn't used in the original circuit. Cool. So now I have an efficient power supply that I can throttle from 0V to 12.5V (full power) to the Peltier.

Next, I need a thermostat to control the power supply and also reverse the polarity of the Peltier device (to switch from heating to cooling). I thought about using an Arduino to do the whole thing: sense the temperature, provide a UI with LCD and buttons, process the PID loop, and send output to the power supply. My biggest worry was the UI. There are actually a lot of parameters in a PID loop, and I didn't feel like writing code to make all of them user-selectable. I also had another Eurotherm 2132 PID controller (same as the aquarium project) which I really like. I decided to use the Eurotherm and build a circuit to convert its output into a control signal for the power supply.

The Eurotherm has two outputs, a relay and a driver output for an external solid-state relay. I removed its internal relay and directed the relay's coil wire connections to the Eurotherm's rear terminals. I then used an optoisolator to interface the Eurotherm's floating outputs to the rest of my signal-converter circuit. The Eurotherm can be configured so that its output 'cycle' for each output is 1 second. Thus, it essentially outputs a PWM signal at 1Hz for cooling, and another 1Hz PWM signal for heating. I wrote a little code for an Atmel AVR ATMega8 that reads the two control signals from the Eurotherm and outputs a voltage that controls the Peltier power supply. It does this by generating high-frequency PWM and smoothing it with a simple R-C low-pass filter. The current draw is very low. The AVR also controls an NPN transistor that drives a DPDT relay. The relay will reverse the polarity of the Peltier device.


All of the above-mentioned circuitry is crammed into an acrylic box that I made for this project (left). The Peltier module has a small heatsink and a large heatsink with two fans (right).





I modified the power supply (by removing a fuse, and adding a fan), and tested it with two Peltier devices hooked in parallel. It seemed fine at 12.5V and 7A.

The next step is to mount the Peltier devices onto the brew tank and test it out.

The tank will hold 5 gallons. For thermodynamic analysis, I will assume it's water. So, that's about 20 liters, and water has a specific heat of 4.2J/g*C, so the tank will require 4.2(20)(1000)=84KJ to change 1*C. If the Peltiers are consuming 12.5(7)=88W, and are 50% efficient, they will be pumping about 44W (in cooling mode), which is 44J/s.

In order to change the tank's temperature by 1*C, the system will need 84000/44 = 1900 seconds, or 30 minutes. This is good and bad. The good news is that the tank will remain very stable, as it is not in danger of being quickly influenced by the Peltier. The bad news is that the tank must start out fairly close to the target temperature, or else it will take a long time to be regulated by the system.