Centrifuge...

[Jens]

I never used a multiple pass CF, but I do not like the idea of running clean oil back into dirty oil until you get most of the dirt. How long, or how many passes would you filter dirty water using this method before you would take a drink?

In a fluid powered centrifuge the retention time is extremely short and you have no control of either rpm or retention time. Both are critical for good results.

Having said that, the classic open bowl CF is not that good either. To get a good cleaning job you need to control how and where the oil enters the bowl. I spent some time playing with an open bowl to see if I was getting some visible particles splashing out of the bowl, or was the oil not staying in the bowl long enough. Turns out splashing and low retention time were both problems.

Both of these issues can be resolved in design (retention time with adjustment of feed volume, splashing by careful setup of introduction of the oil)
The feed cone was not available when I built my setup. I designed my unit to take an add-on feed system but never actually built it because it worked well without it. Having said that, if I would built a new centrifuge I would add the feed cone simply to avoid the erosion of the bowl where the material is introduced to the bowl.

Here are some youtube clips that will show what I am talking about.

http://www.youtube.com/watch?v=1X7Lr-gdxZY

http://www.youtube.com/watch?v=DIZT-jmyphs

In this clip the feed cone system is an older style. Even better feed systems are available now from Simple Centrifuge and other suppliers. I just happen to like the guys at Simple Centrifuge and I think they were the first to offer the feed cone.   

http://www.youtube.com/watch?v=fTOUHf87uHY

Impressive visualization technique with the dye! The business with splashing is (IMHO) related to stationary liquid hitting the bowl and being atomized while a virtual hurricane is happening in the centrifuge which grabs the small bits of atomized liquid and spills some over the top. A feed cone introduces the liquid at the same speed as the bowl so there is no atomization happening and no spilling. Again, even without feed cone my results where excellent but the feed cone would improve on that.

Building your own can be done. But it is not as easy as it would first appear.     

I am not sure if you are referring to the whole centrifuge or just the feed cone but yes, I severely underestimated construction time for the centrifuge!

[glort]

I have been in the veg game for 8 years now and used the settle and filter method with circulating the oil to dry it.
Every now and then I read about the CF's and think maybe time to revisit the idea.
I have had my reservations about the things but have seen good results from them.  For all their flaws, either design does work.  Efficency is another matter all together and so is cost.

Looking at the links Fuel farmer put up, I was impressed with the new design with the bowl cover which I think was an obvious design which should have been apparent from the start.  The splashing and limited retention time was very evident to a friend and I when we spent a couple of hours setting one of these up for a someone else.

The thing that gets me still with these things is the cost and complexity.  Sure they may get the oil many times cleaner than needed but they still don't dry it and that is a HUGE drawback to me.

I personally consider Drying more important than filtering.
If you get unfiltered oil and put it in your tank you get a blocked filter and gunk in your tank. either is annoying but easily and cheaply rectified. If you use wet but perfectly clean oil, you get growths in the tank and lines and risk damage to the ip and injectors that will ultimately lead to their failure and expensive overhaul.
Every time I have got slack or rushed on the drying for more than a couple of tankfuls, it's caused me trouble.

Obviously water content is an infinite variable but I'm not sure if many people realise how much moisture is just picked up from the air alone.  Unless oil will pass a Hot pan test, I won't use it.

I really think CF's are an overkill on cleanliness. People go on about how clean their oil is without realising that diesel is only filtered down to 10 UM and no one has problems with the dirt in that.  I filter my oil to 5 or 1 UM, depending on what filters are available and they cost me under $5 ea.
Recently I let my supplies get low and didn't have time to let my oil settle as normal. as such I was using a filter for every 200L batch I did.
After a couple of batches I put a thick cloth over a drum and filled it about 1/3rd full of oil and let it drip through which took about a day.  I then put that oil in the processor and that one bit of prefiltering the unsettled oil made a huge difference and I was getting about 600L through on a filter.
With oil settled for 6 Months to a year, I can put 2500L through on a filter with no problems at all.

When I just looked at the price of these CF's There is no way in hell I can justify $1500 for a CF ( -IF- I can get one here for that price) that doesn't even dry the oil which to me is essential.  The worst that can happen with my oil is that I will block a filter on the engine a bit more often.
$1500+ buys a hell of a lot of filters both for my processor and all my vehicles and engines.  On the stationary engines I use the $2 disposable type and they last a heck of a long time.  At worst case scenario, the filters I use on the processor doing even the bare min 200L each are also too cheap to compare to any cost saving of a CF.... that still doesn't dry the oil like the processor I built for next to nothing but would cost no more than $150 to do from scratch.

Each to their own and I know there are a lot of pedantic people that have to do things to overkill in order to sleep at night but the reality is CF's are overly expensive,  Overkill for whats needed as far as cleaning the oil goes and don't dry it.

I'm really not concerned with having to change a fuel filter every month not that I ever have to. I'd say I go through about 4 a vear on the vehicle and I get those for nothing and even my wife can change those in under a minute.  On the engines, well I mostly change them because I haven't played with the engine for a while and the fuel in them goes funny so I just go nuts and reach into the pile and spend another $2.

Given the run times and heating I read of with these things, the energy consumption of CF's is overkill as well. I can easily filter 200L of oil to 1 UM AND dry it way more than a HPT will pick up in an hour easily. The greatest majority if not all filters are going to pass particles a lot larger than 1um so going finer is pretty pointless.  It's like using the entire contents of a bucket to fill a teacup.

Really, all a CF saves you is a reduction in fuel Filter changes.  Even if I spent $100 a year on filters, the payback time on a CF that doesn't dry the oil is just way too long to be viable to me.
There are other ways of getting more than acceptably clean, Dry oil a lot cheaper, energy efficiently, with less hands on time than with CF's.

No doubting CF's work but the drawbacks and cost are significant .

[fuelfarmer]

There is nothing magical about a CF. Gravity and time will do most of what we do when using a CF for veggie oil processing. Waste motor oil is another story.

You don't need a vehicle to get around, and it is cheaper to walk. But most of us want to speed up the process.

A CF can save time and space. But that also comes at a price. If you have time and space to process oil a CF could be a waste of money.

Sometimes it is just fun to play with "toys" that have some value in motivating a person to improve the fuel making process. And a CF is cheaper than a bass boat 

[glort]

Space could certainly be an issue.
I live on a suburban house block but I have enough IBC's to use in rotation to give a good settling time for my oil.
The processor itself would be smaller than most CF setups with their tanks etc. For people hat can' sore much oil for any reason, a CF may be valuable.

I think I rather put the money into a boat than a CF but I do realize other people have proclivities different to mine and if spending money on something gives you reassurance and allows you to sleep well at night, then that is worth an awful lot.

[AdeV]

I live in an area with almost unprecedented power stability. I think we've had one unexpected outage in the last 5 years, and that only lasted for ~4 hours (and made national news - it did take most of Liverpool/Wirral out).

So, any kind of Lister for power generation, whether on red diesel or reclaimed veg/motor oil is - essentially - me messing about. If my Portuguese Plan pans out however, I will initially be needing some kind of on-site motive power, and the Lister seems ideal. Since in Portugal, access to "red" diesel (low-tax fuel) is extremely restricted, using veg/motor oil would seem to be the answer...

[Henry W]

I posted some centrifuges.

http://www.microcogen.info/index.php?topic=3256.msg36360#new

Henry

[M61hops]

Hi everybody, geez, never know what you'll find when surfen the web  !  I started a thread on the 'roid forum a week or so back on making a centrifuge!  Somehow I'd missed this thread or I wouldn't have started one over there.  Now I'm pissed off because this thread got more replies than the one I started  !  I can't justify spending over $1100 for a pre-made unit because I don't have a big need or supply of used oil.   But I've got a lathe and milling machine so I was thinking of starting with an old pressure cooker and a brake drum and I'll see what I can put together.  At the moment I think I'll make a belt drive spindle so I can spin the drum up well over the speed I'll run it at to see if it will hold together.  I think a brake drum will work well.  I wish I had 2 the same so if I explode one I'll have one to use  .  In the area where I live there are no old cream seperators or used machinery dealers or even scrap metal places to pilfer.  I did score an old jucier that I might try to solder a strip of stainless sheet metal into the bowl of to make a quick and cheesy 1000g trial unit.  I'll let you guys know what I come up with if I get something working!               Leland

[glort]

You reminded me of something.....
There was a guy, Sunwizzard, on the burnveg forum that made an effective fuge out of a Juicing machine some years back.

http://www.burnveg.com/forum/about8.html

If I remember correctly there was a much longer thread with the usual idiotic questions from the nitpickers on the info pop forum.

Might be something you could look at and save you some time and effort.

[billswan]

Hello

For everyone reading this thread you all should go to you tube and search for home made centrifuge.

There are quite a few clips of differing builds.....

A few weeks ago I ran across one where some guy used a automatic transmissions torque converter as a bowl. I should have copied the link back here but was to pressed for time and thought I would be able to find it later but so far no luck.
Now a torque converter with part of one side removed  should be able to reach very high RPMs without the fear of centrifugal deconstruction so to say 
It is bowl shaped as quick as anything just need the drive and tank for it to set in.......

Be a lot easier than an aluminum bowl construction or the risk of iron brake drums.

Billswan

[deeiche]

SNIP
A few weeks ago I ran across one where some guy used a automatic transmissions torque converter as a bowl. I should have copied the link back here but was to pressed for time and thought I would be able to find it later but so far no luck.
SNIP

Billswan

thanks for the info, I found a thread on 4btswaps where there are pics of a torgue converter based centrifuge.