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Pollution and harm of hydraulic machinery oil

2018-04-27

The oil tank cover is caused by the alternation of hot and cold, which causes the moisture in the air to condense into water droplets and fall into the oil.
Water mixed in 1. oil
1．油液中水分进入的途径
(1) The oil tank cover causes the moisture in the air to condense into water droplets and fall into the oil due to the alternation of cold and heat.
(2) The seal of the cooler or heat exchanger is damaged or the cooling pipe is broken, causing water to leak into the oil.
(3) The humid air entering the system through the hydraulic cylinder piston rod seal is not tightly condensed into water droplets.
(4) When using oil, it takes human moisture and the water absorbed by the affinity between the oil and water when exposed to a humid environment.
 
2. Oil mixed with water after the harm
(1) When a certain amount of water is mixed into the oil, the hydraulic oil will be emulsified and turbid. If the anti-emulsification ability of the hydraulic oil itself is poor, after a period of time, the water cannot be separated from the oil, so that the oil is always in a white and turbid state. This white turbid emulsified oil enters the hydraulic system, which not only causes the internal rust of the hydraulic components, but also reduces its lubrication performance, aggravates the wear of the parts, and reduces the efficiency of the system.
(2) After the iron metal in the hydraulic system rusts, the peeling rust flows in the hydraulic system pipelines and hydraulic components, spreading and spreading, which will cause the entire system to rust and produce more peeling rust and oxides.
(3) Water will also interact with certain additives in the oil to produce pollutants such as precipitation and colloids, which will accelerate the deterioration of the oil.
(4) The action of sulfur and chlorine in water and oil produces sulfuric acid and hydrochloric acid, which aggravates the abrasion and wear of components, accelerates the oxidation and deterioration of oil, and even produces a lot of sludge.
(5) these water pollutants and oxidation products, then become a catalyst for further oxidation, eventually leading to blockage or jamming of hydraulic components, causing a series of faults such as hydraulic system failure, oil distribution pipe blockage, cooler efficiency reduction and oil filter blockage.
(6) In addition, at low temperatures, water is condensed into tiny ice particles, and it is also easy to block the gap and dead mouth of the control element.
 
2. oil mixed with various impurity particles
The solid pollutants in the oil are mainly in the form of particles. Some of these impurities are residual during component processing and assembly, some are produced during the working process of hydraulic components, and some are derived from the intrusion of external impurities. The hazards are:
1. Various particulate impurities in the oil can cause harm to pumps and motors. When impurity particles enter the gear end face of the gear pump or gear motor and between the two end cover side plates, tooth tops and housing, or when impurity particles enter the vane and vane groove of the vane pump or vane motor, between the rotor end face and the oil distribution plate, stator and rotor (blade top), or when impurity particles enter the plunger of the plunger pump or plunger motor and the plunger cylinder body hole, between the rotor and the oil distribution pan, the sliding shoe and the inclined plate, and the sliding pair of the variable mechanism, it may cause stuck failure. Even if it does not cause stuck failure, it will increase wear. Impurity particles may also block the oil filter in front of the pump, causing the pump to produce cavitation or cause a variety of concurrent failures.
2. Various particulate impurities in the oil will cause harm to the hydraulic cylinder. Particulate impurities will cause strain and wear on the piston and cylinder, piston rod and cylinder head holes and sealing elements, increase the amount of oil leakage, and reduce the volumetric efficiency and effective thrust (tension). If the particulate impurities jam the piston or piston rod, Will cause the cylinder to not move.
3. Contaminated particles in the oil can cause harm to various valve components. Pollution particles may cause the slide valve stuck or throttle 121 blockage, resulting in valve failure, even if there is no stuck or blocked fault, pollution particles will also make the valve components movement pair premature wear, with the clearance increased, performance deterioration.
4. Pollutants breed bacteria, aggravate oil aging, make oil black and smelly, and further produce pollution. Such a vicious circle may have the following consequences:
(1) Pollutants block the oil filter, causing the oil pump to empty, causing vibration and noise.
(2) Pollutants increase the friction of the cylinder or motor, resulting in crawling.
(3) the pollutants make the servo valve and other components with poor anti pollution ability completely lose their function.
(4) Pollutants block the pressure gauge channel, so that the pressure is not properly transmitted and reacted.
 
Intrusion air in 3. oil
The air in the oil mainly comes from loose pipe joints, not tight component joint surfaces, tubing exposed on the oil surface and seal failure, and the oil exposed to the atmosphere will also dissolve into the air. In addition, when the amount of oil in the oil tank is small, the circulation of the hydraulic oil is accelerated, making it difficult to remove bubbles. At the same time, the oil suction pipe of the oil pump is not deep enough to make air easy to enter.
The air mixed into the hydraulic system is usually suspended in the hydraulic oil in a bubble state with a diameter of 0.05~0.50mm, which has a serious impact on the bulk elastic modulus of the hydraulic oil and the viscosity of the hydraulic oil in the hydraulic system. As the pressure of the hydraulic system increases, Part of the air is mixed into the hydraulic oil, and the rest still exists in the gas phase. When the amount of mixed air increases, the volume elasticity coefficient of hydraulic oil drops sharply, the pressure wave propagation speed in hydraulic oil slows down, and the dynamic viscosity of the oil increases linearly. The air suspended in the oil combines with the hydraulic oil to form a mixed liquid. The stability of the oil depends on the size of the bubble, which has a significant impact on the hydraulic system. There may be vibration, noise, pressure fluctuation, instability of hydraulic components, crawling of moving parts, reversing impact, inaccurate positioning or disordered movement, etc. At the same time, the power consumption increases, the oxidation of the oil accelerates and the lubrication performance of the oil decreases.