The Boys' Bugle

A Christian magazine for boys featuring things of both a spiritual and physical nature.

Friday, June 22, 2007

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.


  • At 8:09 AM, Blogger Grumpy Gubbe said…

    Thank you for sharing this. I am not happy with my filtering set up either and whilst there is a centrifuge in the US called simple centrifuge for half the price you mention, by the time I get it to Sweden it is too expensive for me. I too am looking into a DIY solution - I'm not there yet either.

    Best wishes

  • At 4:11 PM, Blogger Melvin Martin said…

    Thanks for your comment. I looked at the simple centrifuge website. I want something much faster than their machine. I'm working at building a centrifuge. I ordered most of the parts today.

    Melvin Martin

  • At 8:30 AM, Blogger steve said…

    There is a company who is making nice components for DIY wvo centerfuges with plans for a working model.

  • At 5:25 PM, Blogger Vincent O'Sullivan said…

    I would be very interested in hearing how you got on with your centrifuge project. Be sure to update your blog when you've built it.

  • At 10:02 AM, Blogger smid87 said…

    Hey guys, This is not really that hard. Just contact a Machine shop and have them manufacture a bowl that is balanced and has a 90 degree lip on top. Find a decent electric motor, then build the catch basin (this can be painted steel). This should not cost but a few hundred dollars, and is a far cry from the thousands they want for other centrifuges. They other option is to look into a dieselcraft or similar centrifuge. I think another name is spinner 2.

  • At 2:05 PM, Blogger Melvin Martin said…

    Here is an email I recieved. Melvin

    Hi Steve,
    My name is Paul, from PA. I read your article about using the separator for WVO---

    I am trying to understand in more detail the modification you did with the pipes in the cone.

    I see you did away with all the cone fins, but i can't tell from the picture if you used short pieces of pipe welded to a flat piece or used round pieces,,,,,,or even if you may have 1/2 pipes going away from the center shaft...

    The reason for all this is to get the dirty oil as far to the outside of the cone as possible, right??? So the dirty oil doesn't slide right up the shaft as soon as it enters into the cone.



    1978 Mercedes 300D
    Living with the Amish in PA

    Ephesians 6:10-20--Armor on!

  • At 2:07 PM, Blogger Melvin Martin said…

    Hi Paul,

    Yes, you have the right idea. The pipes were to get the oil to the outside edge. It also was to get the oil to the bottom of the rotor. I think to get the oil to the bottom of the rotor was more important than to get it to the outside of the rotor.

    The pipes where (if I remember right) 3/8 fuel line cut to the same leanth for balance. I used wire to fasten them into the rotor. I didn't weld anything.

    I also had a much smaller cream seperater that I only had to remove the cones to get it to work right. Not all seperaters are the same.

    The cone shape of the cream seperator rotor, for some reason, fills a little bit with dirt in the bottom, then the dirt works it's way up the cone and out the exit hole. I don't understand it, but a cone shaped rotor has very little dirt holding capacity. My big centrifuge has a flat top and works a lot better.

    A cream seperater is good for a small operation.

    A centrifuge is a must for cleaning vegetable oil. I wouldn't do without one again if I had any choice.

    If you run the oil through cold, it will take the "chicken fat" out.

    If you run it hot (150-250 F.), it will take extremely fine dirt out, and take the water out.

    I filter after the centrifuge but it's hardly necessary.

    If you have any more questions, just ask.

    Melvin Martin

  • At 7:49 AM, Blogger Davide said…

    I finish the building of my DIY centrifuge this monday.
    It works at very high speed, 7000rpm with a 230mm rotor, internally 208mm, for 5700G!

    You can see photo at in folder "centrifuga".
    Cheers from italy!


  • At 9:43 PM, Blogger mike said…

    the lowest price for a centrifuge is to go to i think i have it correct well $129 and free shipping will clean 55 gallons an hour need more info contact me mike frawley 619-322-9999

  • At 12:21 AM, Blogger Uncle Dave said…

    Hi guys:
    By trial and error I went from making biodiesel to just using used frier oil straight from the restaurant, by filtering through a J cloth to remove the lumps and then using an old electric cream separater with the dishes removed to clean oil for my '91 volks golf. I ran only in the summer when the weather was warm and switched back to diesel in the fall. I ran for two summers with ever having to change the fuel filter in the car and never had any trouble with injectors etc. Separater cost me $100. Best investment I ever made and was perfect for making my 40 litre batches.


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