Cleaning Vegetable Oil with a Centrifuge

Last summer and fall we had some trouble with our injector pumps and pipes from bacteria in our diesel fuel and vegetable oil. We started to use anti-bacteria fuel conditioner and all our problems vanished.
But this spring I thought it seemed like a few of our injector pumps were showing signs of wear. I wasn’t convinced I completely found the cure to my problems. I didn’t know if I’m filtering fine enough. Or perhaps bacteria had made acid in my oil that I wasn’t getting out. Or perhaps all the problems I was having was either from old bacteria dirt in the pipes or was just my imagination.
A friend mentioned about using a cream separator to clean the oil. I borrowed a hand crank cream separator from my brother-in-law and tried it. It worked very nicely, but it was very slow and didn’t hold very much dirt, and it was hand-crank. I tried to find an electric motor to turn it, but I couldn’t find one that turned the right speed. Then I got a big cream separator from another friend that had a pulley and mounting for an electric motor. It was an answer to prayer. I was pleased. I put an electric motor on it. It worked, but I had to install pipes in it to get the oil to flow right so the dirt would stay in it (the designers weren’t thinking of me when they designed it). My separator has a 7.5 inch rotor and the rotor spins about 7000 RPM.
I took all the disks out of the cream separator so the rotor is just an empty “can.” I heated the vegetable oil up to 140-230 F. for running through the separator. I run the oil through a screen just before the separator. I prefer the hotter temperatures so the oil is very thin, especially if I suspect any water in the oil. The dirt flies to the outside edge and stays there. The clean oil flows to the top and comes out the milk hole. Nothing comes out the cream hole.
After 50 to 250 gallons (depending on how dirty the oil is), I need to stop the machine and clean the dirt out. If I run it too long, it will fill up with dirt and stop cleaning. The only way to know when it needs to be cleaned out is after some experience. Because of the cone shaped rotor of the cream separator, it holds an amazingly small amount of dirt until it starts to come out with the clean oil.

The whole setup with the heater tank in the background and the barrel to catch the oil to the left. The white bucket is to catch any oil that happens to come out of the cream spout.

I am very pleased with how clean it makes the oil. The finest dirt it takes out is so fine it’s like grease. I probably could fool you into thinking it was dirty wheel bearing grease. I ran 750 gallons of centrifuged oil through a 0.5 micron Greasel (Golden Fuels) filter bag. It didn’t so much as discolor the filter. I did get some bigger dirt in the filter that looked like it would have come out of my cooling/storage tank and pump and pipes. I also got a small amount of “chicken fat” in the filter because I filtered it at 80 F. and I was working with thick oil. But it was clean “chicken fat.”
Even though I’m getting the oil cleaner with the centrifuge than the filter gets it, I still get a significant amount of dirt out if I run the oil through twice.

The rotor when it needs to be cleaned out.

Sometime along the line I decided to try to buy a real centrifuge. I just about bought a Diesel Craft centrifuge, but I didn’t like the idea of having to run the oil through it 3 or 4 times to get it clean. I found a rebuild centrifuge just like I wanted for $6500. It was way too much money for my operation to afford. I decided I could make one just as good for a lot less money (including my time) because I have most of the parts already and I have a lathe and milling machine. I was told of a fellow who can balance it for me. But I plan to wait until next fall or winter to build it. Perhaps I’ll find one for a price I like before I get around to building one.
Sometime I want to try to clean used engine oil, transmission oil, etc.
I think the centrifuge will make the biggest difference on vegetable oil that is very thick, because the thick oil holds the dirt with normal, natural settling, but the centrifuge is finished before the oil has a chance to cool off and get thick.
I was told that American fuel is very dirty compared to European fuel. My goal is to get my vegetable oil as clean or cleaner than American diesel fuel. I don’t think I’m there yet.