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Frequently asked questions from the customers installing new machines

Frequently asked questions for lubricant control

Answer : Frequently asked questions from the customers installing new machines

Why is Electrostatic Oil Cleaner superior to conventional filters?

The EOC is able to remove very fine contaminants including oil oxidation products to sub-micron levels and also it removes deposits from system internals.

How small is a particle the electrostatic oil cleaner can remove?

Theoretically, any particles present in oil can be removed. In other words, anything that is not soluble in oil can be removed. For the actual example, we were able to eliminate about 0.02µm level carbon sludge in the compressed oil used in hydropower plant.

Does the electrostatic oil cleaner remove additives in oil?

Since additives are dissolved in oil, they are not removed.

What is the collector life?

Using the electrostatic oil cleaner of an optimum size and for normal contamination level, it is empirically found about 2000 hours between exchanges.

Answer : Frequently asked questions for lubricant control

Is there any relationship between oil leaks and dirt ?

There is a close relationship. The oil temperature increase as mentioned above lowers an oil viscosity (viscosity is halved when oil temperature increases by 10℃) Thus, when a piping connection is loose, oil starts to leak out. For the early stage of leakage, cleaning oil to lower the oil temperature should prevent further oil leaks.


Bubbling does not stop in spite of oil changes.

Air bubbles are introduced when strainers and/or filters are clogged or the piping connection loosens, causing suction of air. Clean the strainers and filters, check and retighten the loose piping connection between the oil tank and the pump.


Does oil viscosity decrease while in use?

No, the viscosity does not change.
You should not check the viscosity of oil in use by fingers. It must be measured at a constant temperature. At the plant, one measures viscosity of new oil when it is cold, and oil in use when it is hot, which is an obvious reason why the oil viscosity seems to have changed.


Is it possible to use a hydraulic oil whose color has changed?

Since oil is a pressure transmitting medium for the hydraulic machine based on Pascal's principle, the color is irrelevant. The color changes are due to oxidized products reacting with very small amount of nitrogen compounds in oil (a few tens to a few hundreds of ppm) resulting in coloring. Therefore, there is no alteration in basic properties of oil.


What is the oil degradation?

It has been misconceived that "degradation" means being unable to use because of total loss of oil properties. But nearly for all cases, it means that it is contaminated.. Removing contaminants, oil can be used for a long time. However, the additives, very important in oils, are consumed during service, and thus they have to be replenished by adding oils. Generally, by keeping oil always in normal conditions, one can reduce the additive consumption as well.


What kind of dirt is harmful for oil?

(1) Dirt from outside is usually metal oxides of more than 10µm in diameter. They cause the sliding part to be abraded and generate finer abrasion powder. When a machine is in normal operating conditions, the lubrication is in a fluid lubrication stage, (where oil film is about 1µm thick) or in an elastic fluid lubrication (where oil film is 0.2 -0.6µm). If the oil film is thinner than that, metal-to-metal contact should take place. Therefore, dirt becomes the culprit of abrasion when it enters oil film, i.e., the dirt size may be less than 1µm.

(2) Such metallic abrasion powders as generated by fine dirt act as catalyst for oxidizing and ultimately forming oil-insoluble resin-like materials, i.e., sludge. It is this sludge that causes all kinds of lubrication problem: valve malfunctions; clogging strainers and filters; deteriorating the heat temperatures to lower viscosity resulting in poor lubrication as well as oil leaks.
Summarizing these, one can understand why dirt as small as one micrometer or less must be removed.


Why is it necessary to know Total Acid Number (TAN)?

(1) Among the fresh oils, some have high TAN, hers low TAN - this depends on the acidic materials used in additives. Generally speaking, a new oil of low TAN increases its TAN during service. While a new oil of high TAN decreases its TAN during service, but it starts to increase, reversing the trend, when service is further extended.

(2) Increase of TAN means generation of organic acids through oxidation of a very small portion of oil - TAN is indicated by amount of KOH expressed in mg necessary to neutralize all the acidic materials in 1 gr of oil.

(3) As oil is oxidized, oil-insoluble resin-like materials are formed to become sludge. Sludge is the major culprit of malfunctions of hydraulic machines, and it should be prevented in advance from occurring through monitoring TAN. Import is not TAN itself but prevention of sludge and its elimination once formed.


What effects does water in oil have?

Water present in oil induces rusting metals by adhering to the metal surface. The rusted metals are then released into oil, acting as catalyst to accelerate oil oxidation. With water present, the acceleration for oxidation is a few tens to a few hundreds of times as fast as without - it is more dangerous than dirt in some sense.

It is very difficult to eliminate water, in particular when emulsified. But, our product, DH elements can do it by one to a few passes.


How many years can oil last?

It can last for any number of years by making sure that: oil temperature does not exceed 60℃; oil is always kept clean; and occasionally oil addition is made.

Essentially, it depends on how well one takes care of oil.

Also, once in a while, one should examine the state of oil properties via sampling in order to determine if it can still continue.