Technical Information
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 Click here for our Oil Purification Brochure September - 2007 (472kb)
Oils in use, what happens to them and how can "Oil Purification" help?
How do oils get dirty and wet? How do they degrade?
Any oil when exposed to normal conditions in a plant will start to pick up moisture immediately it is exposed to the air. Oil is very hygroscopic and picks up moisture easily. Moisture levels in an oil will normally increase to a maximum of about 300 PPM. and then stabilize. These levels are normal and will cause no damage.
If the oil is used in a "total loss" application, such as a drip feed, pick up of moisture and dirt is not a factor as the oil is used once then discarded.
Most oils however are used in enclosed reservoir’s and re-circulate through the operating system. As the oil re-circulates, it lubricates, cools and flushes away debris from normal wear particles. This debris, depending on the size of the particle, may settle out by gravity in the oil reservoir, be removed by the filters, or simply be recirculated if it is too small to be removed. This recirculated particle is able to cause more damage by abrasive wear, each time it is re-circulated. Information developed in the last few years shows that particles as small as 5 microns, if present in large quantities will cause severe pump and valve wear by acting as a "lapping compound".
A lot of dirt is also introduced into the oil reservoir by airborne dirt. Very few oil reservoirs have efficient air filters on them. Dirt particles light enough to float in the air as dust, are drawn into the reservoir every time the oil level in the tank goes down. When this happens some of the dust particles settle out into the oil. Oil reservoirs where the level changes frequently can pump many times their volume of air every hour. This exposes the oil in the tank to very large potential amounts of dirt. This mechanism is how the new oil delivered from most oil companies becomes contaminated with dirt.
The additives present in most oils contain various chemicals to give long life to the oil. These consist mainly of antioxidants, rust preventatives, anti-foam agents, de-emulsifiers etc.
Water, heat and oxygen are the materials that separately or together will cause damage to both the base oil and the additive system. Water will react with many oil additives and hydrolyze them. When this happens the water reacts and fractures the additive into two or more other chemical fragments. These reaction products may or may not be oil soluble. They may also act as catalysts for the further decomposition of the oil or additive.
Oxygen will react with both the additives and the oil to form oxidation by-products. These by-products will generally be of a acidic nature initially and may also act as catalysts for further oxidation.
The antioxidant protects against oxidation only so long as it is present in sufficient quantity. When it falls below a certain value it will become less effective. As it is further reduced it will become completely ineffective.
Antioxidant is used up slowly under normal conditions. It protects by actually being consumed as it reacts with and neutralizes the initial oxidation products. Heat and the presence of moisture will both accelerate the consumption of the antioxidant.
The effect of this is shown in Chart # 1, which is a generalization (not actual figures) of what will typically happen in real life.
The top line represents the additive level and starts at 100%. After a period of time, the level drops slowly until it reaches a point where it will start to drop rapidly.
At about this point, the first signs of oxidation will appear, they may be measured by TAN increase or some other function.
As the additive level falls below some critical number (depends on specifics) the rate of oxidation will increase. Oxidation by products will self catalyze more oxidation, so the more of them there are present, the faster oxidation will occur.
Eventually the degree of oxidation will reach the point where the lubricant must be removed and replaced with new oil. Reclamation at this point is not recommended.
Chart #2 attempts to show graphically what can happen if the oil is reclaimed properly at regular intervals. Purification is not a valid solution once the oil has severely degraded, as at the end of the example above, but used properly, before severe damage has occurred it can give great benefits.
The top line again represents the additive level. As in the previous scenario, it drops slowly due to consumption. A very small amount of oxidation takes place. Instead of doing nothing and letting nature take it’s course, the oil is Reclaimed and THE ADDITIVES RESTORED TO THEIR ORIGINAL LEVELS.
The additives start the next cycle from a very high level and the same scenario takes place. Again a very small amount of oxidation takes place. The oil is reclaimed again and the additives restored. The net effect is that oxidation is controlled at very low levels, water and contaminants never build up to troublesome levels, Oil Life can be extended MANY TIMES!
We have demonstrated at many customers over the last twenty two years, that this system works.
The financial benefits in extending oil life in machines is actually threefold. The two more obvious ones are;
- The cost savings in buying new oil because of longer oil life and
- The cost savings from disposal.
The major saving comes out of the process where you extend the life of the oil by improving the system. If you improve the preventive maintenance and keep the oil system cleaner, the system will operate better and longer than it would without the improvements. Maintenance costs will be lower and productivity will be higher.
Filtration Improvements
The best type of filtration is full flow filtration after the supply pump. Unfortunately this will be the most expensive option. In some machines is just not possible to easily find a point where the system can be split to put this in.
Make sure that there is a suction strainer in the supply line to the pump.
If you can’t put full flow in, then at least put in "Kidney Loop Filtration". This can usually be added to the reservoir, even if you have to cut in new access points for the filter/pump unit. Filter the reservoir capacity typically every hour. Remember you will be adding to the total flow through the reservoir so the retention time for settling and air separation will be reduced.
Use as fine a filter as possible. Start with a large capacity "nominal" filter and follow it with an "absolute" filter. Most machines will see a big difference going to even a 10 micron absolute filter. Finer is better. New equipment using a lot of servo valves will REQUIRE at least 3 micron absolute filters.
Leave the filtration loop running all the time, even when the machine is shut down. This gives the filters a chance to catch up with the normal debris generated and clean the system up while it idles.
If you are getting moisture in the oil DO SOMETHING ABOUT IT! Don’t ignore it. Moisture is the single most damaging item in oil maintenance.
Remember you will be using additives up. While continual filtration will keep the oil clean, you will be depleting additives and these need to be checked by your oil supplier.
Purification is NOT a panacea, it won’t solve all problems or give indefinite life to all oil systems. But used properly it can save a lot of money and extend the life of a lot of oils and oil systems SIGNIFICANTLY.
I’d like to define some terms at this point, some of these are ours, some are in general use.
View Definitions & Terms
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