WVO Cleaning Methods/Steps
After Collecting here are the most common steps to pre-filtering or pre-cleaning-
Step 1 – Settle
This is my favorite step because it requires us to do nothing. Just let the oil sit and allow gravity to do the work for us.
Gravity – Our filtering ally!
-Oil is lighter than water. With enough time and heat, the water and even much of the dirt will settle to the bottom of whatever the storage container is, i.e. cubie, barrel, tank. Settling is key and is something we all use.
How long do you settle? As long as possible is the short answer. It really depends on the contamination of the oil and temperature. We find out through a process of trial and error as to how long is necessary. If you are plugging your filters easily(i.e. after 30 gallons of oil) then you should let the oil settle longer. To speed up the settling process you can heat the oil with sunlight or other forms of heat, like band heaters for barrels.
Step 2 – Filtration and Centrifuging
Once the oil has been properly settled, it’s time to run it through a filter or centrifuge. Either pour the oil off the top of a cubie, or pump it off of the top of your tank, barrel, tote etc.
Filtration media –
Filtering is best done in stages, starting with a course filter(inexpensive and catches the large particles) and ending with a water blocking fine filter(with an absolute rating and water block to catch the really fine particles)
Literally anything porous can be used as a filter: House screen, blue jeans, old sheets, etc. You can get screens that fit nicely over the top of barrels. Also, bag filters can be used which are hung like bags and oil is dumped or pumped through. Many folks also use house water filter housing and cartridges for initial filtering. Their filter media is not good for final filtering as they don’t have an absolute rating. Most filters do not block water either. They need to say something like “waterblock”. Water blocking filters have a poly coated membrane which swells and absorbs water.
Final Filtering –
“Spin on” or cartridge filters. Many people use these for initial and final filtering. Diesel truck filters are often used with a micron rating of 10 absolute, with waterbock!
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Centrifuging – This is an extremely effective, sure and simple way of “force-settling” the oil, de-watering it and cleaning it to. Oil can be cleaned and completely dewatered in one pass, making this a time and space saving solution. When filtering large quantities, centrifuges are an obvious choice. They are becoming more and more popular due to their simplicity and effectiveness.
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PHO or Partially Hydrogenated oil, is creamy at room temperature. Sometimes it’s called “creamy liquid fry shortening”. This needs to be heated up to filter it. It takes more work. I always aim for the clear liquid at room temperature oil, it makes collecting and filtering much easier.
Absolute vs. Nominal Micron Rating
Most filters have an Absolute or a Nominal Micron rating. Absolute means absolutely no particles bigger than the stated rating will pass through the filter. Nominal means it only stop some, not all of the particles of the specified size
So, you can use a 20 micron nominal filter for intitial filtering, but do not rely on it for final filtering. House water filters are only nominal.
Remember 10 micron Absolute
What is suspended water? I’m glad you asked, but you may not be…
Suspended water is water molecules trapped in small pieces of solid matter suspended in the oil. Suspended water is not removed by the typical settling/filtering process. One way to remove this is to add another step, so it would be settling/filtering/settling. Suspended water will settle after it has been filtered down to 10 micron, and applying heat will hasten the settling. Another way to clean your oil of suspended water is by using a centrifuge.
Vegetable oil soaked rags and fabrics may spontaneously combust if left crumpled up long enough. It is a safe practice to properly discard all soaked rags, towels and filtering fabric as you finish using them finished. I don’t ever leave used rags around. Spontaneous combustion is more likely after fabrics have been washed and reacted with laundry detergent chemicals.
If your on-board or vehicle filter clogs up quickly, like less than 1000 miles, you are not cleaning your oil well enough.
Hot Pan Test and/or Crackle Test– This is the widely accepted test for water in oil. It involves heating oil so that any remaining water turns to steam and bubbles. If you have no bubbles once heated, then you are water free! If the oil is popping and bubbles are bursting then you have free water.