How I built my bulk pasteurizer
I wanted to put together a parts list and breakdown of my second pasteurizer build after I had a chance to run the first one for a few months and address some of its flaws. I could not find a ton of info on the builds or pasteurizers so here is how I did it.
I purchased the stock tank from tractor supply. Its a 3x8 tank. https://www.tractorsupply.com/tsc/product/countyline-oval-galvanized-stock-tank-3-ft-w-x-8-ft-l-x-2-ft-h-300-gal-capacity
I used two furniture dollys on either end of the tank to roll it around as needed. I ran galvanized screws with rubber washers through the bottom of the tank and into the wood of the dollys to secure the tank to the dollys.
A ½” hole was drilled through the bottom of the tank and a pvc fitting with a threaded male end and slip joint on the other side was inserted into the hole. I used red rtv around the joint to seal it and a threaded 1/2” electrical nut to secure the drain in place. I then ran ½” Pvc into the slip joint on the bottom of the stock tank, came down and 90’ed then ran ½ Pvc out the front. I added a ball valve to allow me to control when I drain the water
To support the inner rack that the bags sit on, I chose to use stainless steel tubing (1”x1”x .120) welded together to form a solid surface for the wire rack to sit on. There are a total of 6 supports in the pasteurizer. The top of the support is 9” from the bottom. The 4 supports in the center have a spread of 35”. The two supports on the ends to support the narrower portion of the stock tank have a spread of 12”. I could not justify the cost to run stainless steel wire in my welder so I chose to cover my welds in heat/water resistant paint to prevent rust.
For the rack I used livestock fencing from tractor supply. I used wire shelving from home depot in the first version but found it to not have enough strength to support the weight of all the bags when the pasteurizer was fully loaded. It would sag and bend and not keep the bags where they needed to be. The livestock fencing is proving to be a solid upgrade. Should go without saying but when using a grinder, eye/ face protection is strongly encouraged.
To cut the rack to size, I laid it on top of the stock tank and cut the excess length off with a grinder using a metal cut off wheel. I then cut the outline of the tank, cutting small bits away until the rack fit into place inside. Caution:The cut edges of the livestock fencing are razor sharp after you cut them. Wear gloves when handling it and be careful not to cut yourself.
To round off the edges, take a sanding wheel with your grinder and smooth out the sharpness from your cuts. This will help lower the chance of you getting cut, but the bags will still be susceptible to punctures. To lower the chance of punctures, I took 20’ of ½” hose from home depot, made a single cut down the center and wrapped it around the edges of the stock tank. It serves as a cushion between the sides of the livestock fencing and the bags that sit on top of them.
Possibly the easiest part of the build to think about and plan for, but one of the hardest to make look pretty. Ha. To hold heat in I grabbed 4 moving blankets from harbor freight and a 4 pack of ratchet straps. Get as many friends as you can to help you put the blankets on and hold them in place while you strap them against the stock tank. No fancy work here, with 3 people and no planning we pulled it off okay. It proved to be a bit difficult to keep the blankets folded to the right size of the stock tank without dropping them. Be creative, I am sure there is a better way to pull it off but that is how I did it.
For a lid I used foam insulation board from home depot. I cut it to size with a jigsaw and covered it in a tarp to prevent steam from hitting it. The tarp was secured with duct tape on top. Not the prettiest but it has held up for months.
I have two units to produce steam depending on the run size. They're both CGoldenwall brand steam generators. One is a 6KW unit and the other is a 10.5KW unit. The 6KW unit requires a 30amp 220V circuit. The 10.5KW requires a 50amp 220v circuit. If I am only running one of my bulk pasteurizers, I will run the 6KW unit and achieve run times of around 8 hours with 650 pounds of substrate. I choose to do a single layer of bags when pasteurizing to achieve even heating throughout the bags. If you add a second layer, effectively doubling the run (1300pounds) the top bags will heat up considerably faster and pasteurization is inconsistent in my experience.
For larger runs, I fill both of my bulk pasteurizers. I can steam 1300 pounds at a time using the 10.5KW unit steaming two large stock tanks. Run times are in the 8-10 hour range.
Steam pipe routing
I chose to use a washing machine discharge hose from home depot to route the steam from the generator to the stock tank. I used a brass 90 double female off the steam discharge and connected a a ¾” male to ⅝” barb connection . The hose is slipped over the barb and secured with a hose clamp. For steam distribution in the stock tank I drilled a ¾” hole. I attached a fitting with a threaded 3/4 “ male end sticking into the stock tank and a ⅝” hose barb sticking out. Washers were placed between the inside and outside of the tank, and red rtv was applied around the hole to seal the opening. I used a ¾” nut to hold the brass fitting into place. On the ¾” threaded end inside the stock tank, I attached my copper piping to distribute the steam. It’s a simple “T” with holes drilled in the front so steam is spread in the center and the sides of the tank. If you're unsure about it just be creative. The steam will fill the vessel regardless, you just don’t want it getting spit out on a single area as it will super heat those bags compared to the rest.
If you have made it this far, thank you for reading! There is not a lot of information on the steam generators or really anything surrounding building out the stock tanks and I wanted to try to help those that have reached out about my first build. I will continue to run these and refine the build as time goes on.