Harmfulness of Polluted Oil to Hydraulic System
Click：2898 UpDateTime：2014/2/10 16:52:49
With the production of enterprise there are large expenses for oil annually, which always keeps the production cost at a high level. In order to decrease production cost as much as possible, many enterprises try to save oil expenses, which shows up in changing oil not timely and irregularly. The oil in use does not reach the standard of equipment operation, resulting in oil pollution, re-doing work pieces and even suspension of production to recondition. The losses are serious.
The research of Chinese Mechanical Engineering Society shows that: 80% of mechanical breakdown is caused by frictional wear. Therefore, to improve equipment lubrication, control friction and reduce wear are important measures to save materials, reduce equipment breakdown, improve operating condition, raise the level of quality, reduce pollution, extent equipment service life, save energy, decrease cost and improve economic performance.
Harmfulness of Water in the Oil
1. Low water content: It will accelerate the aging of hydraulic oil. The water will produce chemical reaction with additives in the oil under certain condition, causing degradation or even no effect of certain using performance in the hydraulic oil.
2. High water content: hydraulic oil mingling with water produces emulsified oil, making blocking properties of lubricating oil decreases. Insufficient adhesive force of hydraulic oil to friction surface and damage of oil film can cause abnormal mechanical wear and even result in mechanical breakdown.
Harmfulness of Gas in the Oil
The bubbles in hydraulic oil can damage the oil film, resulting in dry friction of mechanical equipment and even mechanical breakdown!
1. The work performance of hydraulic pump goes bad (Shows up in bad performance of hydraulic pump and its short service life).
2. Noise and vibration: When bubbles flow along with oil to the place in higher pressure, the bubbles are compressed in smaller volume and greater density. At this moment, certain energy is saved inside the bubbles. When the pressure is increased to certain values, the bubbles will explode, produce partial hydraulic shock, make the system vibrate and the partial pressure up to dozens of MPa , and meanwhile produce explosive sound.
3. Hydraulic system is unable to work normally. Once the hydraulic oil is mixed with air, the oil compressing rate will increase largely and the high stiffness of oil itself will reduce greatly, resulting in miswork of performers, failure of automatic control and creeping of working bodies, destroying work stability and seriously harming system’s work reliability. Even air leakage may happen and endanger human safety.
4. Cavitation Erosion: when the bubbles generated from the oil in the low pressure area are carried to high pressure area, they will collapse suddenly and re-condense to fluid, causing the partial area forms vacuum. The surrounding oil flows toward to the collapsing center at very high speed, producing larger partial impact force to the wall surface. The instant pressure can be up to hundreds of or even thousands of barometric pressure. When a great deal of bubbles collapse, the metal side wall will suffer exhausted damage from repeated fierce shocking, causing the erosion of solid wall surface. The erosion caused by cavitation to the surface of solid materials is called cavitation erosion, which is very harmful to system.
5. Speed up hydraulic pollution. The bubble or foam in oil is called intangible contaminant, which is seriously harmful to hydraulic. It makes the oil’s stiffness decreases, volume efficiency reduces and system’s reliability decreases. When the bubbles in the oil is compressed instantly or destroyed, the state similar to adiabatic compression will increase the bubble temperature sharply and then cause increase of oil temperature, resulting in the damage of various additives in the oil, thus, producing free carbon, acid substances and daub sediments, causing oil turns black, accelerating oil degradation and meanwhile causing the metal produces chemical corrosion. Besides, higher oil temperature will cause oil oxidation, decrease oil lubrication performance and speed up aging of seal elements.
Harmfulness of Impurities in the Oil (all suspended solids as well as their sediments which are not dissolved in gasoline and benzene)
1. It destroys oil film and blocks the formation of oil wedge. Solid contact occurs between the friction surfaces of moving parts, causing lubrication failure.
2. The galling and damage fitting on the surfaces decrease degree of finish and fit quality. When it is serious, due to continuous and rapid expansion of damaged surfaces the moving parts bite together, causing damage of machine parts, parking accidents and product abandonment.
3. It speeds up machine parts wear, destroys fit property and precision, enlarges space and reduces transmission accuracy. In the lubricating system inner leakage is increased. Insufficient oil supply decreases system pressure, affecting mechanical efficiency and service life or causing serious problem that the machine cannot work normally the lubrication loses efficiency.
4. It stuffs or blocks oil flow in the filtering devices or running pipelines, causing insufficiency and failure of lubrication and cooling system, bringing sharp temperature rise of friction surfaces and accelerating aging of the oil.
