Frequently asked questions about hydraulic oil
1. Why does the oil temperature rise?
Insufficient oil or oil pollution. Insufficient oil is caused by equipment design defects or oil leakage. Oil pollution, especially oil oxidized pollutants, can easily cause blockage of the cooling system and filters and increase the oil temperature.
2. What is the relationship between oil leakage and pollution?
When the oil temperature rises due to the above reasons, the viscosity of the oil will decrease, and low-viscosity oil is more likely to seep out in the connecting parts. Keeping the temperature low and the oil clean are common methods to avoid oil leakage.
3. How are bubbles produced?
When the filter or the line is clogged or the air passes through a loose connection, the anti-foaming additive in the oil does not work, resulting in bubbles.
4. Why does oxidation increase the viscosity of oil?
The viscosity of hydraulic oil that has been used for a long time will not change, except in the case of particularly severe oil oxidation. Generally, engineers think through experience that the viscosity of oil will decrease after long-term use, but that is generally judged when the machine works at 50-70°C, and the viscosity test is at 40°C. In fact, as the degree of oil oxidation deepens, the viscosity will increase slightly.
Five, oil color problem
Long-term use of oil darkens due to the formation of pigment, which is normal. Because the pigment dissolves in the oil and does not affect the quality of the oil, it is not correct to judge the quality of the oil only by the color of the oil.
Six, deterioration of oil
Oil oxides continue to polymerize oxides to adsorb particles, resulting in a "sand paper-like" effect that is the adverse consequence of oil deterioration. The deterioration of the oil leads to the abrasion of the machine. In fact, the deterioration of the oil is essentially the oxidation of the oil!
7. What size pollutant is harmful to the hydraulic system?
Particles larger than 1um will cause filter blockage or pump failure to hydraulic system. Because the particles of about 1um are similar in thickness to the oil film, they adhere to the oil oxidation pollutants and are adsorbed in the pipeline and valve gaps to wear the pipeline valves.
8. Why test the acid value
The acid value is closely related to the oxidation of oil, which is an important indicator for checking the degree of oil oxidation. Generally, if the acid value of the oil exceeds the standard, the acid value of the oil can be reduced by removing oil oxides.
9. The role of water in lubricants?
The presence of water will cause rust in the circulation system. Rust can cause valve and system problems and accelerate the oxidation of oil. The oil-water separator can remove the water in the lubricating oil.
10. The service life of oil
When the oil is completely purified and the change of the oil below 60℃ is very small, it can be used for a long time. However, lubricating oil is affected by air, heat, impurities, and water, and usually cannot be completely clean and needs to be replaced. At the same time, the consumed additives can be replenished with a small amount of new oil.
11. How to judge whether the oil is water/air mixed
If the oil appears white and turbid, the possibility of solid impurities or liquid viscous impurities can be eliminated, and it can only be caused by water or air. The hydraulic oil can be sampled and tested. Drop the oil sample on a hot iron plate. If bubbles appear (water turns into water vapor at high temperature to form bubbles), it can be determined that there is water in the oil: otherwise, the oil contains air.
12. How to deal with oil entering moisture
If the oil is mixed with water to cause turbidity, let the oil stand for a period of time, let the water sink to the bottom of the oil tank, and then remove the water. However, if the water content is too high and the hydraulic oil is emulsified, the oil needs to be replaced.
13. Treatment method of oil entering the air
If it is determined that turbidity is caused by air mixed in the oil, 1. Check whether the hydraulic system pipeline leaks, and cut off the source of air mixing.
14. Reasons for abnormally high oil temperature
The root cause of the abnormal increase in oil temperature is as follows: First, because the safety valve pressure setting is too low, most of the oil flows back to the tank through the safety valve, resulting in too low work efficiency of the hydraulic system, such as excessive load. Most of the energy will be converted into the heat energy of the oil, resulting in high temperature: the second is the poor cooling effect of the cooling system, which causes the oil temperature to be too high; the third is that the oil circulates too frequently in the oil circuit (often caused by insufficient oil), Causes heat dissipation difficulties and temperature rises.
15. Examination of excessive oil temperature
Fault diagnosis should be from easy to difficult, first check the amount of oil in the tank, if the amount of oil in the tank is insufficient, it should be added to the standard level in time. Pay attention to use the same grade of oil when filling, and filter before use.
If the amount of oil is appropriate, check whether the oil cooling system is blocked. If it is found that the oil cooling system obstructs air circulation, it should be cleaned in time to ensure normal air circulation and facilitate heat dissipation. Sometimes the fan tape is too loose or slippery, which will also cause the fan efficiency to decrease and the cooling effect is not good. It should be checked and adjusted in time, and replaced with new tape if necessary.
If there is no problem with the oil volume, oil cooling system, and fan tape, it can be determined that the set pressure of the main safety valve is lower than the standard value. The pressure setting value of the main safety valve should be adjusted again to the standard value.
16. How to know if the oil is deteriorated or contaminated
The reasons for the dirty oil are: 1. The oil has chemical changes due to long-term use; 2. There are too many impurities and physical changes;
As long as the reasons for these two changes are found, corresponding measures can be taken. In the absence of necessary testing equipment and equipment, to determine whether the oil has undergone chemical or physical changes, a relatively simple and practical method is to use filter paper.
Take a sample of the oil, drop the oil on the filter paper, and observe the oil halo formed. If the layering and splitting of the oil halo is more obvious (dirty in the middle, the closer it is to the edge, the clearer it is), indicating that the oil has deteriorated and must be replaced. Oil; if the oil halo spreads out evenly, it means that the oil has too much impurities. Check the oil filter, replace the filter element, and replace with new oil if necessary.
