Technical Information
3-3. Oil Deterioration
It is inevitable that oil will deteriorate during use, but deteriorated oil is a major enemy of equipment.
This section explains the causes of deterioration and how to check for deterioration.
What is oil deterioration?
Oil deteriorates over time and there are three main reasons for this:
1. Contamination: Generation of sludge, contamination by atmosphere or oil mist
Metal powders generated by wear directly damage equipment, and contaminated air and oil mist affect the oil's components, changing the oil's viscosity and other initial expected performance.
2. Moisture contamination
Basically, there is a problem if the oil does not contain any water (0%).
If the oil contains more than 0.1% water by weight, it cannot be used as it can cause rust in the equipment.
3. Temperature changes
Oil is often exposed to high temperatures, and as a result, it deteriorates due to oxidation and changes in quality caused by temperature changes.
Deterioration due to temperature changes causes the oil to change, so the oil loses its original expected performance.
Lubricant additives in deteriorated mineral oil are the enemy of equipment
As mentioned in "3-2. Oil Viscosity," mineral oil always contains lubricating oil additives.
While the mineral oil maintains its functionality as new oil, this lubricant additive works by bonding stably with the base oil, but as the oil deteriorates, the lubricant additive separates from the base oil and begins to damage metals that the oil comes into contact with.
Lubricating oil additives such as sulfur, phosphate esters, and phosphates have the effect of corroding copper, which can affect the steel pipes used in oil chiller and cause damage to the equipment.
| kinds | Purpose and Function | Typical ingredients | Addition amount |
|---|---|---|---|
| antioxidants | It prevents oil oxidation by reacting with free radicals and peroxides to convert them into stable substances, and inhibits the formation of varnish and sludge caused by oxidation. | organic sulfur compounds Zinc dithiophosphate |
～1% |
| Anti-wear agents | It forms a protection film of secondary compounds on the wear surface, preventing wear. | phosphate ester Zinc dithiophosphate |
5～10% |
| Rust inhibitor | It forms a protection film on metal surfaces or neutralizes acids to prevent rust. | phosphate ester |
1% |
Prevent equipment troubles with frequent checks and replacements
Prevents equipment trouble caused by oil deterioration
Sooner or later, oil will go bad and there is no way to prevent it.
What you need to be careful of is that deterioration can cause the equipment to lose its original function or cause problems with the production equipment itself. To prevent this, it is important to observe the following four points.
- Check the oil level every day
・Don't replenish with the wrong oil
・Prevent foreign matter (moisture, metal powder, etc.) from getting mixed in as much as possible
・Pay attention to changes in the color of the oil
Determining oil deterioration by color (simple colorimetric method using ASTM colors)
As the oil deteriorates, it turns reddish in color.
When determining oil deterioration based on its color, the approximate limit of oxidation deterioration is when the color (ASTM number) of the oil becomes 2.5 or more points darker than that of new oil.
Previous item: 3-2. Oil viscosity
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