definitions & terms

ADDITIVES

Additives in industrial oils will often react with water, oxygen or system metals to create hydrolysis products, which may not be completely oil-soluble. The presence of water, together with high temperatures, will accelerate this process. These reaction products are often responsible for deposits, “varnishes,” sludges and accelerated wear on components. Deposits and varnishes are commonly associated with oxidation by-products, when in fact, these deposits MAY be caused by degraded additives.

The reduction of additive concentration in an oil will also reduce the antiwear properties of the oil.

Go to the top

CENTRIFUGE

A centrifuge removes insoluble materials by spinning a fluid at high speed. The g-force generated in a centrifuge enhances specific gravity differences between different objects or substances, effectively separating them.

In our process, water — which is generally heavier than oil — will flow to the outside of the centrifuge. Dirt particles that are heavier than water will collect at the bottom of the water layer.

Centrifuges will not completely separate either water or dirt from oil, but they can be useful for preliminary treatments, to remove gross contamination. Centrifuges are generally only useful for low-viscosity fluids — the higher the viscosity and specific gravity of the oil, the less effective a centrifuge will be.

Go to the top

CLAY TREATMENT

Many people become confused when talking about filter aids and the various clays used for oil treatment. These are two completely different types of materials. (Filter aids are described in further detail below).

The clays used in our oil purification process (such as Fuller’s Earth) are bentonite clays. When properly pre-treated (or “activated”), the clay will attract impurities, which become chemically attached to the clay, removing them from the oil.

The clays are particularly reactive with acidic materials. During oil oxidation, many acidic by-products are formed; these will oxidize further to produce the sludges and varnishes typically found in severely oxidized oils.

In the field of oil chemistry, it is well-known that these acidic materials are formed in the oxidation process and then act as catalysts for further oxidation. Removal of these materials while they are present only in small amounts will enhance the stability of the oil and extend its life.

Clay treatment is normally accomplished by mixing a specific amount of activated clay with an oil, in a specially-equipped reactor. The oil/clay mixture is heated to a pre-determined temperature, for a very specific time period. The oil is cooled and filtered to remove all traces of clay. Contact at a temperature that is too high or too low will not remove the impurities efficiently. Contact for too long a time period can degrade oil quality and additives.

Clay treatment is particularly effective for removing very small particles of degraded oil additives. These particles are semi-plastic and have been proven to pass through even a 0.45-micron filter.

Go to the top

COLOUR DEGRADATION

Oil companies have invested a great deal of effort into producing light-coloured base stocks. Removal of unstable compounds during the refining process usually removes the materials that are highly-coloured as well.

We have been conditioned by oil companies to think that a light-coloured oil is of “better” quality. As a general rule, when dealing with virgin oils, this may be so — but colour is actually a minor characteristic in oil. The materials that create the colour are present in “parts per million” levels and are difficult — if not impossible — to analyze for specifically

Purified/reclaimed oils will always be slightly darker in colour than new oils. The more times an oil goes through the purification process, the darker its colour will become. This is not necessarily a sign that the oil is oxidizing! It usually means that the colour components are building up slightly in the oil.

Analysis of an oil is the ONLY way to determine if it is starting to oxidize. If the analysis indicates oxidation is not occurring — that the oil is clean and additives are present in the correct amounts — then the colour of the oil is irrelevant. How dark can purified oil get? One of our first customers has been recycling their oil for more than twenty years. This customer reclaims about 80% of the oil they use. Their reclaimed oil has been very dark brown for a long time. Every purified batch is analyzed by the major oil company that originally supplied the new oil. Not one batch has been rejected!

Go to the top

DISTILLATION

Distillation is a process in which a fluid is heated above its boiling point and turned into a vapour. The vapour passes into a condenser, where it reverts to its liquid form. Impurities are left behind during boiling, which results in a purified fluid.

Distilled oil will usually require further treatment before it can be re-used as an effective lubricant.

Go to the top

FILTER AID

Filter aids commonly used are diatomaceous earth or perlite minerals, which are mined, heated to remove organic materials, then ground and classified into various size ranges.

Filter aids are very useful for removal of extremely fine materials suspended in liquids. They are used to clarify many liquids, including water, beer and wine.

The small chambers present in the ground material causes very small particles to become trapped. Filtration of the relatively large particles also removes all the very small particles trapped within them.

Filter aids generally do not absorb oil additives, although some specific additives can be extracted and removed

Go to the top

FILTER RATINGS

Industrial filters have traditionally been rated with an arbitrary number, which was supposed to be the largest size particle that would pass through the filter. In effect, this rating was only achieved when the filter was loaded with particles and almost ready to be thrown away.

A better way to rate filters is the beta ratio. This ratio counts the number of particles per mL in the dirty stream, and divides them by the number of particles actually passing through the filter. The number is based on particles of a particular size. A filter that passes 5000 particles of 10,000 through a 5-micron filter has a Beta5 ratio of 2. A filter passing only 100 particles of 10,000 through has a Beta5 ratio of 100 — and is obviously a better filter.

A filter can have a number of beta ratios depending on its construction.

Go to the top

FILTRATION

Filtration consists of the removal of solid particles by passing a fluid through a filter. The solid particles are removed from the fluid stream by collection on a filter media. The filter media may be paper, fibrous material (i.e. felt), filter aid, diatomaceous earth, or man-made materials. The filter may be a cartridge, belt, or filter press.

Go to the top

I.S.O. PARTICLE COUNTS

Many systems have been developed to measure the cleanliness of an oil. Many of these methods were time-consuming and difficult to implement. Different labs would often produce different results from the same sample

A single oil-cleanliness measurement system is now in use around the world. One milliliter of oil is filtered through an absolute filter, and the particles counted. Only 5-micron and 15-micron particles are counted — all others are ignored.

The particles are broken into groups for each rating class; numbers falling on the line between groups move up to the next group.

The first number reported is the rating for 5-micron particles, and is referred to as the silt level. Silts will cause wear by acting as a lapping compound. The second number refers to the 15-micron group rating — these are also generally considered to cause abrasive wear.

A typical, clean hydraulic system will have an ISO rating of 16/14 or better.

Go to the top

INDUSTRIAL OILS

Industrial oils can be classified into the following general categories:

Go to the top

OXIDATION

In simple terms, oxidation is the reaction of oxygen with oil components. The higher the temperature of an oil, the faster oxidation reactions will take place. Oxidation can never be completely eliminated, but the process can be slowed down significantly by the use of antioxidant additives, and by controlling the temperatures and contamination the oil is exposed to in use.

The first effect of oxidation is generally an increase in “total acid number” (TAN), and the second effect is an increase in viscosity. Along with these effects, sludges and varnishes will likely be formed. These may separate out in the oil reservoirs, or coat the surfaces of metal components and cause a variety of mechanical problems.

Go to the top

PURIFICATION

Purification is the removal of contamination (solid, liquid or dissolved) and the return of an oil to a state where it can be re-used for its original purpose.

Go to the top

RECYCLING

Recycling involves the re-use of an oil product for any purpose other than the original use, and includes such things as conversion to fuel programs.

Go to the top

RE-REFINING

Re-refining uses severe physical and chemical processes to treat an oil.

Now obsolete, an early re-refining technology was to treat the oil with sulphuric acid, separate the acid sludge, then clay-contact the oil at a high temperature. This produced a base stock of average viscosity that was generally only suited for low-grade industrial products like lubricants and cutting oils.

These days, the preferred process is de-metalization, followed by vacuum distillation of the various oil fractions. Distillation is followed by hydrotreating, which further purifies the base stock.

There are other processes, based on solvent extraction, which are presently being commercialized.

Oils produced by distillation and hydrotreating are typically pure enough to be used in high-quality products, and in performance, they are indistinguishable from virgin oils produced by major oil companies. Two or three viscosity grades are typically produced

Go to the top

SEGREGATION

Segregation is the process of separating certain wastes from others, by containing the different waste streams as closely as possible to the source. Each waste should be identified and stored separately from all others.

Go to the top

TOTAL ACID NUMBER (TAN)

TAN is a measuring system for the acidity of an oil. The TAN number on its own does not directly relate to oxidation; many additives used in oils have a significant acid number to start with.

It is very important that the TAN is measured and recorded over time, as this trend will indicate whether an oil is oxidizing or degrading

Go to the top

VACUUM DEHYDRATION

Water boils at 100˚C under atmospheric pressure. Many of the additives present in industrial oils will be degraded relatively rapidly if heated to 100˚C in the presence of water, so when removing water, it is very important to find ways to lower the process temperature as much as possible.

As pressure is reduced, the boiling point of a liquid is also reduced, so a vacuum of about 25 millibars allows water to be distilled off at a temperature of about 50ºC. This reduces “stress” on the oils and additives, meaning that there is no degradation of either during the vacuum dehydration process.

Go to the top

WASTE OIL

Waste oils are either industrial or automotive in origin, and may contain almost any organic liquid not deemed to be hazardous, and large amounts of aqueous waste.

Waste oils are generally disposed of by burning, used as fuel, or re-refined to produce industrial oil base stocks. Currently, only a relatively small percentage is sent for re-refining

Go to the top