During the operation of machinery and equipment, due to the long-term contact with metal and the influence of surrounding air, temperature, pressure, electric field, light and other factors, foreign impurities are gradually added to the oil. As a result, there will be moisture, dust, sand and metal chips in the oil, which will be oxidized gradually during long-term use, resulting in changes in chemical composition and deterioration and harmful impurities. Generally, there are the following categories:
1. Stained by foreign impurities
During the use of the system, the oil is easy to be soiled by various mechanical impurities. There are impurities such as metal dust and sand particles. This is because the metal powder from the friction parts falls into the oil, or the dust and sand are immersed in the oil due to the loose sealing of the system and the machine shell. For example, when the tractor is working in the field and the car is driving on the road, a lot of fine dust and sand will be brought into the engine lubricating oil through the air filter with the air. Mining machinery is often soiled with ore powder.Causes and Preventive Measures of Lubricating Oil Quality Deterioration
The lubricating oil used in machining machine tools and hydraulic oil used in hydraulic equipment are often stained by chip dust and other metal powders of machined parts. These impurities have a very bad effect on the quality of system oil. It will heat the machine like abrasive and wear the parts prematurely.
2. Turbid by water
When oil works in mechanical equipment, water often seeps in. This is because the lubrication system, hydraulic transmission system or water cooling device of various mechanical equipment are not tight enough, so that water flows into the oil. In addition, the water contained in the air can also be absorbed by the oil, because the oil has water absorption, and its water absorption is determined by the ambient temperature. For example, the dissolved moisture of transformer is closely related to the temperature of transformer oil.Causes and Preventive Measures of Lubricating Oil Quality Deterioration
3. Thermal decomposition
There are many kinds of oil. When it comes into contact with high-temperature parts of mechanical equipment, such as in the combustion area of engine fuel, when it comes into direct contact with red hot metal in quenching, and when it comes into direct contact with high-pressure arc in oil switching, it will suffer great local overheating until partial combustion occurs, and the oil can be heated to a very high temperature. At this time, Breaings the oil is thermally decomposed (cracked), resulting in the formation of colloid and hard coke, which is called coke deposition.Causes and Preventive Measures of Lubricating Oil Quality Deterioration
Carbon deposit is very harmful to automobile engine, because carbon deposit is a poor conductor of heat, and the combustion chamber wall and piston top are covered with carbon deposit, resulting in poor heat dissipation, resulting in overheating and damage of parts and other accidents.Causes and Preventive Measures of Lubricating Oil Quality Deterioration
During the use of system oil, the main reason for chemical changes is the role of oxygen in the air. When oil works in the equipment, with the increase of oil temperature, contact time, contact area and contact pressure with air, the oxidation degree of oil will be accelerated and deepened.Causes and Preventive Measures of Lubricating Oil Quality Deterioration
The result of oxidation makes the oil produce some harmful substances, such as acids, colloids, asphalt and so on. Due to the continuous increase of oxides in the oil, the color of the oil darkens, the viscosity increases and the acid value increases. There is precipitated sludge in the oil, so the content of impurities in the oil increases again. The oxidation of oil often causes faults to the system.Causes and Preventive Measures of Lubricating Oil Quality Deterioration5. Diluted by fuel oil
During the operation of various internal combustion engines, the lubricating oil of automobiles and tractors and aviation lubricating oil seeps into the lubricating oil due to the incomplete combustion of some fuel oil (diesel and gasoline) and gradually dilutes the lubricating oil.
The degree of dilution of lubricating oil by fuel oil is related to the structure and working conditions of the engine and the type of fuel oil. The waste aviation lubricating oil contains an average of 2% ~ 3% aviation gasoline, 10% ~ 15% vehicle gasoline and 30% ~ 50% tractor kerosene.Causes and Preventive Measures of Lubricating Oil Quality Deterioration
It can be seen that the higher the flash point of the fuel oil used by the engine, the more fuel oil will be infiltrated into the lubricating oil, and the lubricating oil will become more diluted. This will reduce the flash point and viscosity of the lubricating oil and lose its proper lubricating performance.
The quantity of undesirable impurities generated by the oil in the system operation is not allowed to increase indefinitely. When it reaches a certain degree, it will not meet the requirements of the system for oil, so this oil becomes waste oil and needs to be replaced. Causes and Preventive Measures of Lubricating Oil Quality Deterioration
If it is not replaced and continues to be used, the wear of moving parts will be accelerated, the system will fail, and the service life of the equipment will be reduced.
How to determine whether oil products should be scrapped is a more complex problem, because different service conditions and different requirements for oil of various mechanical equipment need to be determined in combination with the actual use situation.Causes and Preventive Measures of Lubricating Oil Quality Deterioration
2、 Prevention methods of lubricating oil quality deterioration
The reason for the deterioration of lubricating oil quality is not only mainly produced in the working process, but also the oil will be stained due to the improper management of the staff. Therefore, it is very necessary to try to prevent premature deterioration of system oil, prolong service life and save oil. Some precautions to prevent oil deterioration are summarized as follows:Causes and Preventive Measures of Lubricating Oil Quality Deterioration
1) All kinds of oils must be used according to the specified purpose, because adding oils of different types or substandard quality to the machine can cause various adverse consequences.
2) In the process of oil handling or oil distribution, use specified sealed containers and tools, and do not put the oil into dirty containers to prevent the oil from getting dirty.
3) When refueling the machine, pay attention not to let dust, dirt and moisture fall into the oil, because the service life of the machine largely depends on the cleanliness of the oil.
4) Although the oil is not easy to volatilize, it is often lost due to overflow and leakage when filling the machine or container. Therefore, be careful not to lose the oil during operation and when adding oil to the machine.
5) When filling oil tanks and drums, do not exceed their capacity limits. A space must be reserved in the container for the thermal expansion of the oil to avoid the leakage of overflow after the thermal expansion of the oil.
6) Always check the tightness of the machine shell, the cover of the system oil reservoir and the connection of the pipe, tighten the connection of the parts or replace the sealing gasket to prevent oil leakage.Causes and Preventive Measures of Lubricating Oil Quality Deterioration
7) After discharging the waste oil and before filling with new oil, the system shall be thoroughly cleaned and wiped.Causes and Preventive Measures of Lubricating Oil Quality Deterioration
8) The water and oil sludge deposited in the engine oil should be removed regularly or continuously.Causes and Preventive Measures of Lubricating Oil Quality Deterioration
9) Keep the lubrication of the machine in good condition and prevent the parts from being greatly worn, because the clearance increases after the parts are worn, and the oil will be more polluted.Causes and Preventive Measures of Lubricating Oil Quality Deterioration
10) The temperature of oil generally does not exceed 50 ~ 60 ℃. When a lot of heat is released, the cooling conditions of oil shall be guaranteed.
11) In the air compressor, the temperature at the outlet shall not exceed 160 ~ 170 ℃.
12) Lubricating oil filters shall be installed in automobiles and tractors to make the lubricating oil continuously fine filtered during operation, so as to prevent the lubricating oil in the engine from becoming waste oil due to the accumulation of mechanical impurities and oxidation products.