Written by Rickdatech

The drier your oil is before making biodiesel, the better your biodiesel will be. One of the oldest techniques used to dry oil for making biodiesel is the heat and settle method. In this article I will repurpose an old appleseed water heater for this task. It's a 53 gallon AOSmith water heater I purchased a few years back and has served me wonderfully as an appleseed. I'm using a steel water heater stand as a base because the Best Practices Manual suggests minimizing both wood and plastic in our designs.

I'm using stainless steel and galvanized plumbing where possible because it's going to be exposed to the weather. Around here steel and cast iron turn to rust quickly when exposed to the weather. There probably is some coating that will stand up to the occasional splashing with oil and biodiesel as well as harsh UV exposure; I just haven't found it yet. So, since I already have most of what I need for this project in stainless and I'm really tired of working with rust, I'm going high tech.

Since I'm mounting the water heater upside down for better draining, I had to drill holes through the stand to clear the drain pipe. I used a hole saw to cut clearance holes over all the plumbing connections so they can be accessed from below if I need to change or tighten anything. I've drilled a dozen clearance holes for sheet metal screws near the outside edge in order to securely attach the stand to the water heater.  

The Site Tube

We need a site tube to show us how much oil we have loaded. If we don't have enough oil to cover the element good, it will burn out when we turn on the heat.

I'm using a polyethelyene tubing temporarily for my site tube. I plan to upgrade it to a PTFE site tube in the near future. So far I've only found PTFE tubing in 25 ft minimum lengths. at a couple dollars a foot, that makes it an expensive addition. I have plans for some more equipment with site tubes in the near future, and I'll upgrade them all at the same time.

I've put a valve at the bottom of the site tube. I'm only going to use the site tube to indicate how much oil is in the tank. After filling the tank, I'll close the valve so it doesn't drain the tank if it becomes damaged for any reason.

Adding Insulation

The bottom of this water heater is not insulated. In fact I have not seen one that was insulated on the bottom. When a water heater is right side up, it doesn't need any insulation on the bottom since heat rises and there is almost no heat loss through the bottom. But, I'm turning mine upside down and if I don't insulate, it will lose heat too fast. I'm insulating the easy way, with spray foam insulation. I drilled holes in the sheetmetal cover and filled the void with foam. As the foam cured, it expanded and came back out the same holes it went in. After a day of curing, a razor blade and some silicone will clean and seal it all up. After filling the void on top, I added a 1/2" sheet of styrafoam insulation. Now, I can heat it to 150F and it will take more than two days to get back down below 100F.

Temperature Guage

I've installed a wireless BBQ grill thermometer. It has a probe that I have slipped between the insulation and the tank. The sender is sitting on top of the tank. Now I can check the temperature from anywhere on the property.

Safety Concerns

The two main areas of concern are electrical safety, and fire safety.

Electrical safety is all about not getting electrocuted. We do that by following good electrical wiring procedures. Make sure our electrical connections are all covered with no bare wire exposed. Make sure the tank is grounded properly, and use GFCI fault protection on 110V circuits. The best thing you can do is to get an Electrician friend to look over your work.

Fire safety has three main areas here, the first is to make sure we never overheat our oil, the second is to make sure we have no leaks or drips that could cause spontaneous combustion, and the third is good housekeeping. Kitchen fires are the most common type of fires in homes in the US, and they almost always caused by overheating oil. The intrinsically safe way to do this job is to heat the oil indirectly. Indirect heating is typically heating water elsewhere and piping the hot water or steam over to the settling tank. That's how commercial plants do it. Indirect heating is too complicated and too expensive for home brewing equipment.

This project uses the less expensive direct heating with multiple safety shutdowns. We use two snap discs that shut off the electricity when it reaches a certain temperature, and a timer. The idea is to use various sensors and switches to shut off the flow of electricity. This method is not fool proof. It is possible for the controller to malfunction allowing the heating element to overheat the oil. A routine check of the electrical system should help prevent malfunction from happening.

Spontaneous combustion can be and has been caused by oil soaking into a fibrous insulation of a heated oil tank. It is simple to prevent with this type of tank, watch for leaks and fix them promptly. 

Oil expands when heated. If the vent is closed, it can build up pressure. To keep the pressure low enough to prevent the plastic site tube from rupturing, I've added a pressure relief valve set to 30 psi and a pressure guage to periodically test the relief valve.

Good housekeeping or keeping our workspace neat, clean, and organized will go a long way towards preventing accidents and fires. Make sure you have the materials you need to clean up oil spills right away. Make sure you have a fire extinguisher nearby. Don't leave hoses stretched across walkways. These all sound like common sense. They are, but common does not mean 'without thought'. Pay attention to the details of your work area with safety in mind.

The One Shot Element Controller

This Element Controller will let the element heat until it reaches temperature, then shut off until it's turned back on manually. It also has a failsafe timer that will cut off all power when it times out. And finally if there is an interruption in power, it will again shut down until it is manually restarted. The wiring diagram below is for 120V wiring.

To operate it, set the timer for a little longer than it takes to heat the oil up to temperature, then push the green button. To turn it off, push the red button. The light will come on when the element is heating.

Bill of Materials